UNITED STATES DEPARTMENT OF THE INTERIOR FISH AND WILDLIFE SERVICE FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE VOLUME 57 BULLETINS 107 TO 125 ISSUED BY THE FISH AND WILDLIFE SERVICE 1956-58 UNITED STATES DEPARTMENT OF THE INTERIOR FISH AND WILDLIFE SERVICE Bureau of Commercial Fisheries TITLE PAGE AND INDEX VOLUME 57 ISSUED 1962 U.S. GOVERNMENT PRINTING OFFICE • WASHINGTON, D.C. • 1962 CONTENTS OF VOLUME 57 Bulletin No. P;i(;^' 107. V.vLiDiTV OF .\r,K detp:kmi.\'ation from sc.\les, .\.\d growth ofm.vrkedL.\keMichig.\n L.vKE TRoiT. Bv Louellii E. C'uble. (Issued October 1956.) l-.')!t 108. (_''OMP.\R.VTIVE STUDY OF FOOD OF BIGEYE AND YELLOWFIN TUNA IN THE CENTRAL PaCIFK'. B3" Joseph E. King and Isaac I. Ikehara. (Issued October 1956.) 61-y the fishermen. Initially, the officers removed the fin scar from each fish (in some cases, also a scale sample) and sent them to the Institute for Fisheries Research of the Michi- gan Department of Conservation in Ann .\rl)or for payment of the reward. Later, however, most of the fish weic shi])ped iced, either in the round or (hcssed," to the Institute where the scale sam- ples were taken, measurements recorded, and the deformed or missing fin described in some detail. Sex was not recorded. Vp to July 22, 1952, 1,603 fish had been sent to the Institute for Fisheries Research. Of this number, 96 could not be identified with any one of the three plantings or lacked essential records: ?'. e., record of the missing fin was lacking, the fin or combination of fins rcporteil missing or ab- normal had not been used in the experiment, or fins were reported by the State observer as normal in every resptH't, length measurement was not re- coi-ded, or scale sample was not taken. For the 1 ,.507 fish that, on the basis of fin records alone, could have been marked lake trout, the annual recoveries were as given in table 2. Al- though this group includes individuals with "natinally (h'formed" fins (malformations not resulting from earlier clipping), tlie data of table 2 give a rougii estimate of th(> percentage return from the several [jhnitings. Because it is (loui)tful that the recoveries from area 8 were fish with l)()na fi(h" markings, the percentage of returns arc shown for aieas 1-6 only. Recoveries from the 1945 planting exceech'd those from the 1946 planting almost 4:1, aiul c.Nreeded recovei-ics from tile 1944 " tvills and \ iseera n'lnoveil. planting 11:1. but the I'ccoveries of marked lake trout from all plantings were in exceedingly small percentages of the numbers of fish released. About 0.67 percent of the marked lake trout re- leased in 1945 but only O.Oti percent of the 1944 planting and O.IS percent of those planted in 1946 were recovered. The low |)ercentages of return and abrupt termination of ca|)tiires probably were due to the rapid reduction of the population by the sea lamprey. Xo explanation can be ottered for the higlu'i- percentage of return irom the 1945 than from the 1944 and 1946 plantings. A large majority of the recoveries of marked lake trout in northern Lake Michigan (areas 1-6) were made in the fourth year after planting. The fish had evidently reached a sufficiently large size at that age to be most easily caught in the nets employed in the fishery at the time. The localities and relative numbers of recov- eries are shown in sectional maps of Lake Michigan (figs. 1 and 2). Bouiithiries of tliese sections are superimposed on a map of tiic entire lake (fig. 3) to indicate their position with reference to the houiuhiries of the statistical areas or districts 1-8 regularly employed in analyses of commercial fishery statistics for the State of Michigan waters of Lake Michigan (Van Oosten, Hile. and .lobes 1946; Hile, Eschmeyer, and Lunger 1951). The largest catclies of niaiked lake trout were made out of Manistitiue, Mich., in area 2, and in the vicinity of the islands of areti 3, with the great est concentrati'in about lieaver Ishiiid and tiie shoals to the east of tiiis island. A few s[)ecinieiis were caught in each of areas 1, 5, and ti; 2 trout, taken just across tlie line in tiie northern i)art of area 7 by fisliernieii from I'entwater, are included witii tliose caught in area 6. .\o recoveries were made between Little Saliie Point in the nortltern FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE NAUBINWAY Scale of Miles TRAVERSE CITY Figure 1. — Northern Lake Michigan showing points of release and capture of marked hike trout. Phmting kjcations designated as follows: 1944, square enclosing an X; 1945, circle enclosing a +; 1946, triangle enclosing dot. Re- coveries from the three plantings are indicated as follows: 1944, squares; 1945, circles; 1946, triangles. The sizes of the symbols indicate numbers of fish recaptured at the various points, the smallest symbol of each year class is for 1-4 fish thro\igh the largest for more than 49 fish. part of area 7 and tlie vicinity of South Haven (area 8), more tlian 60 miles distant, where 102 lake trout with deformed or missing; fins were taken. Lake trout witli ahnormal fins, captured on the Wisconsin side of tlie lake, are not shown on the map. Most of tlie 142 fish taken were caught north of Algoma; a few, 1 or 2 off each port, were taken off Two Rivers, Cedar Grove, Milwaukee, and Racine. The records on tliese fisii are not sufficiently detailed for profitable study. Rather than iTJect individual fish arl)itrarily all samjjles, pioporly documented and iiaving "possible" fin markings, were accepted for study. The large size of certain lake trout whose missing fins in<- tions l)ut a summary of tlie basis for the rejection of the samj)les from area S is given at tliis |)()int. GEOGRAPHICAL DISTRIBUTION OF RECOVERIES In areas l-(>, tiie earliest reeoveries were made near the loeality of planting. As the fish grew oldei- and larger the captiiies were more widely disti-ibuted. They scattered to some extent in all directions, hut the principal movement was in a northwest I'lly direction toward Maiustiqiie and thence westerly and southwesterly until some fish were recaptured along tlie Wisconsin shore. Captures of lake trout with deformed fins were fewer and the distribution was discontinuous southward from the localities in which the plant- ings were made. No recoveries at all were made between the extreme northern part of area 7 and the neighborhood of .South Haven.'" If it is as- sumetl that lake trout reported off South Haven were actually marked fish, it is difficult to under- stand why none were caught in the heavily fished 60-mile-long area en route to the more southerly waters. On the other hand, if the lake trout reported from area 8 are considered to be wild- stock lake trout with abnormal fins, the trouble- some question arises as to why no trout of the same category were reported from that 60-mile stretch." The discontinuity of distribution of the recoveries does not provide convincing evidence, but does, nevertheless, give cause to regard with suspicion the genuineness of the mark (deformed fin) on the fish caught at South Haven. FINS ON RECOVERED LAKE TROUT Records of degree of regeneration of the pectoral fins '- in terms of regenerated rays (table 3) and lengths of the abnormal fins (table 4) on recovered lake trout were similar in that they suggested no basis for the separation of marked "> \'an Oosti'ii (19511) dcsciibcd the distribution of rccovprios of these sanu' fish tlirougli 1949. Subsequent captures did not chanKe the general situation greatly, except that the progressive scattering of the growing fish continued. " The answer possibly may lie in the enterprise of a single fi.sherman. Of the 102 recaptures from southern Lake Michigan, 94 were turned in by the same operator. Conceivably fishermen in the waters to the north observed similar al)normalities hut did not believe them to be thi' result of fin-clipping. " The collection of fish with dorsal and adipose fins dijjped is too small to give reliable results, but 43 (75.4 percent I of a total o( 57 specimens were jurtgi'd to have true marks. .lust one lake trout with this mark was caught in area 8. The mark (dorsal and adipose fins removed) proved somewhat confusing becau.se of the presence of fish w itll oni' fin deformi'd anil the other normal. 37832G O — 50 2 lake trout of areas 1-6 from naturally propa- gated individuals of this region, but did indicate rather conclusively that the samples from areas 1-6 and area 8 could not have been drawn from the same population. Despite certain disagree- ments as to detail between data on the right and left pectoral fins of trout frotn areas 1-6 (dis- crepancies which could have been the result of the small number of fisii recaptured with a deformed left pectoral fin), the general situation can be de- scribed satisfactorily from the combined records of the two fins. The extent of regneration of fins on lake trout from areas 1-6 was relatively small. In a total of 1,348 individuals, 57.5 per- cent had no regeneration of the fin rays, and 77.5 percent had fewer than 5 rays regenerated. With respect to length of regeneration, 58.2 percent of the fins were without regeneration, and 75.2 percent were not more than K normal length. In area 8, to the contrary, regeneration of most fins was advanced. Of 74 fish, for which there were records of the number of rays in the de- formed fin, but 1.4 percent had no rays regenerated, and only 4.1 percent had fewer tlian 5 rays re- generated as compared with 77.5 percent in areas 1-6. Of 89 fish, for which the length of the fins was recorded, just 1.1 percent of the fins were without regeneration, and only 13.5 percent were not more than ji normal length as compared with 75.2 percent in areas 1-6. The very small percentage (1.1) of fins showing no regeneration in area 8 is strikingly difl'erent from that (58.2) of fins on fish from areas 1-6. The data of tables 3 and 4 have a usefulness in addition to that of demonstrating that samples from areas 1-6 and area 8 were drawn from stocks that were dissimilar with respect to the character- istics of abnormal fins. If the thesis is accepted that most or all of the lake trout from area 8 were unmarked, it can be anticipated that most of the unmarked lake trout in the samples from areas 1-6 also will be among the fish whose fins exhibit more advanced regeneration. DISCREPANCIES BETWEEN AGES READ FROM SCALES AND INDICATED BY ABNORMAL FINS Agreement between ages indicated by fins and read from scales was high (substantially above 90 percent) in fish from areas 1-6, but in area 8 only 39.2 percent of the scale readings agreed with the ages indicat(>d bv abnormal fins. p]ven 8 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE Table 3. — Extent of regeneration of the pectoral fins,, expressed as number of rays, on lake trout marked in 1945 and 1946 Locality of recovery and mark; year of planting offish Number of rays regenerated >8 Unknown Areas 1-6: Eight pectoral (1945) Percenta?e ' -_ Left pectoral (1946) Percentage Ritiht and left pectorals Percentage Area 8: Right pectoral (1945).,.. Percentage Left iiectora! (1946) Percentage Right and left pectorals. Percentage 271 i.348 679 65.0 96 36.8 774 57.5 91 8.7 29 11.2 120 9.2 46 4.5 9 3.5 55 4.2 43 "69" "in2 1 2.4 1 1.4 31 3.0 10 3.9 41 3.1 1 3.0 2.4 2 2.7 36 3.4 10 3.9 46 3.5 48 4.6 13 5.0 61 4.7 3 9.1 3 4.1 30 2.9 17 6.6 47 3.6 1 3.0 2 4.9 3 4.1 25 2.4 14 5.4 39 3.0 1 3.0 1 1.4 17 1.6 28 10.9 45 3.5 2 6.1 2 4.9 4 5.4 41 3.9 33 12.8 74 5.7 26 7.5.8 35 85.4 60 81.1 I Fish with unknown number of fin rays not included in percentages. Table 4, — Extent of regeneration of the perioral fins, expressed {for most fish) as a fraction of the normal length of the fin, on lake trout marked in 194-5 and 1946 Locality of reco\ery and mark; year of planting Number of fish Extent of regeneration No regener- ation Less than t/ij-inch long normal length normal length normal length H W normal normal length length 45 42 4.2 3.9 27 17 10.2 6.4 72 59 5.4 4.4 13 6 34.2 16.8 10 14 19.6 27.6 23 20 25.9 22.5 Full normal length No record of length Areas 1-6; Right pectoral (194.6) Percentage ' Left pectoral (1946) Percentage Right and left pectorals. Percentage Area S: Right pectoral (1946)..-. Percentage Loft i)ectoral (1946) Percentage Right and left pectorals. Percentage 1.077 27! V.iis 679 63.8 95 36. 774 58.2 43 "59' 162" 1 2.0 124 11.6 48 18.2 172 12.9 1 2.6 2 3.9 3 3.4 18 1.7 2,7 26 1.9 1 2.6 4 7.8 6 5.6 21 2.0 8 3.0 29 2.2 2 5.3 1 2.0 3 3.4 128 12.0 60 22.7 188 14. 1 15 39.5 IS 35.3 33 37.1 0.8 2 (1.8 10 U. S 1 2.0 1 1.0 1 Fish with fins of unknown length not included in percentages. though this percentage was somowliat higher than would be expected from an assumption of complete iiulcpeiulcnce of age shown by abnormal fins and by scale markings, it does indicate that if the sample from area 8 contained any authentic marked lake trout, their number was extremely small. GROWTH AS INDICATED BY ABNORMAL FINS Presentation here of details on length frequen- cies and average sizes of various age groups of the different year classes as established by abnormali- ties of the fins and by the examination of the scales would be little to the point as the situation is described adequately by the data of table 5 which shows the mean lengths and ranges of length for the several age groups (year classes combined) as indicated by fins. If these lake trout are taken as bona fide fin-clipped fish, we must accept also tlie conclusion that the trout were largest in the first and second years of life (average lengths of age-groups I and II, 23.8 and 17.1 inches, respectively), were smaller, and, for the most part, without growth in later years (range of 12.5 to 12.7 inches for average lengtlis of age-groups III-VI, and only 13.7 inches for age-group VII)." Despite the consiilerable range of length for each age group of lake trout of known Tablk .5. — Average lengths and ranges in length iif age groups as indicated by the occurrence of abnormal fins '{assumed to be true marks) of lake trout from southern Lake Michigan [See text discussion of the probability that few or none of these fisti c luld have come from the various fin-elipping e.vperiments] Number offish Total length (inches) Average Range I - 4 13 28 22 19 13 3 23.8 17.1 12.7 12.7 12.5 12.6 i:i. 7 22. .5-24. n --- 10 4-24. HI - 7.4-21.0 IV 10. 4-2:!. V 10. 4-1.6. 2 VI 10.0-16.6 VII - - 13. 2-14. 5 '" According to Smith and Van Oosten (1940) lake trout tagged at Port Washington, Wis., that averaged 12.8 inches long at tagging were 19.8 indies long about 2 years later. AGE DETERMINATION FROM SCALES OF LAKE TROTIT 9 age that will be demonstrated later, some of the ranges in table 5 cannot be considered reasonable. These lines of evidence, even though they do not exclude the possibility of the presence of a few marked lake trout in the samples from area 8, demonstrate conclusively that the great majority were unmarked wild stock, and that the occurrence of abnormal fins among these fish was not related to the age of the fish. The sample is, therefore, considered unsuitable for use in the present study. Samples from areas 1-6 undoubtedly also include some unmarked fish with abnormal fins; and con- vincing evidence of their presence will be offered. There is no reason to believe they were sufficiently numerous there to harm seriously the materials for the purposes of this investigation. VALIDITY OF AGE DETERMINATIONS FROM SCALES The study of the scales of lake trout, presum- ably of known age, ofTered the rather perple.xing problem of using the same materials for two pur- poses which, in a sense, are mutually exclusive. It was, of course, imperative to examine carefully the scale characteristics of a large series of fish of known age to establish, as exactly as possible, criteria for the determination of age. It was equally necessary to use the same fish as the basis for an objective estimate of the degree of accuracy to be expected in the reading of the scales of lake trout for which the ages are not known. With a small series of fish, accomplishment of both purposes would be impossible, for the investi- gator would become so well acquainted with the scales of individual specimens as to remember their characteristics, especially their unusual features, and hence would be unable to make ob- jective age determinations. In the present large series of 1,405 fish from northern Lake Michigan (areas 1-6), however, memory of scales of indi- vidual fish probably had no biasing effect on the accuracy of successive readings. Even so, pre- cautions were taken to keep the tests objective. A brief statement of the general procedure follows. In a preliminary examination, designed to estab- lish whether or not the scales of lake trout bear markings that can be interpreted as annuli corre- sponding in number to the supposed age of the fish (as indicated by a deformed or missing fin), the scales of several hundred lake trout were read objectively. They were studied for the occurrence of repetitive irregularities in the sculptured pattern without reference to any information about the fish except the date of its capture. When such markings were found, readings and measurements made from them were compared with tlie full data on the individual fish. Another important aspect of the first series of examinations was the establishment of the time of annulus form- ation and the progress of the season's growth, without knowedge of which it is difficult to make accurate readings from scales of fish caught over much of the growing season. After the characteristics of the annulus and the time of annulus formation were well established, the entire series of scales was read twice. During both readings the only information available was date of capture, and eacli second reading was made without knowledge of the age assigned at the first. After completion of the two readings, a careful study was made of the scales of all lake trout for which the ages assigned were not the same at the first and second examination and a best estimate of the correct age was made. EARLY GROWTH OF SCALES The scales of lake trout are cycloid, oval to egg- shaped. Concentric ridges or circuli, arranged about a focus, roughen the outer surface of the scale. The focus may be central or slightly anterior or posterior to the center of the scale (see figs. 8 and 11). Neither radii nor transverse grooves are present. The inner surface of the scale lacks circuli but is not utterly smooth and characterless. Annuli sometimes are clearly visi- ble on this side. The scales are so small, thin, and deeply embedded in the skin as to be relatively inconspicuous. They are dislodged with such difficulty that few are regenerated. Variation in the number of scales, in series along the lateral line, is large, from 180 to more than 200. Squa- mation of the body is complete. Only the head, which is well supplied with mucus pores, and fins, are unsealed. The size of the scale varies greatly from one location on the fish to another. In general, the larger scales are on the posterolateral surfaces of the body and the smaller scales about the fin bases 10 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE and Oil the aiiteroveiitral and aiiterodorsal surfaces. Samples for study were taken from a mid-point on the body, below the anterior part of the dorsal fin, immediately above the lateral line, and thus did not include either the smallest or the largest scales of the individual fish. However, scales from rather limited areas show considerable variation in size and shape. Scales chosen from the sample for study were tliose which seemed most repre- sentative of the larger symmetrical scales. The scales of lake trout appear during the sum- mer of the first year of development. However, neither the age nor the length of the fish at the time of scale formation lias been determined definitely for the lake trout in I>ake Michigan. Both salt-water and fresh-water fishes that have been studied develop platelets, the beginnings of scales, when the yoinig fish are from about 18 to 50 millimeters in total length (Fish 1932; Hilde- brand and Cable, 1930, 1934, and 1938; Cooper 1951 ; Brown and Bailey, 1952; and others). Fisli (1932) described a lake trout larva 21.5 millimeters long from Cape Vincent Hatchery, but did not mention the development of scales. A yolk sac was still present at this size and the appearance of scales would scarcely be expected before ab- sorption of the yolk. In 1953, young lake trout 26 to 56 millimeters long, were taken in Lake Superior in the middle of June and the middle of August by the Fish and Wildlife Service research vessel ( 'isco. The largest of those caught in August was 56 millimeters or 2?i6 inches long. It had a band of scale pockets containing platelets along the entire length of the lateral line. This band consisted of several rows of platelets on either side of the lateral line. The sizes of the platelets were graduated; the larger ones were adjacent to the lateral line; the others became smaller and farther apart with each suc- cessive row. Only in tiie lateral line did the scale structures take alizarin stain readily. These structures were concave ovoids, two in each pocket, one dorsal to and the other ventral to the lateral-line organ, forming partial sidewalls to it. The platelets, situated in dermal pockets, were protected from immediate <'ontact witli tiie alizarin. Consequently, the scale pockets stood out as clear areas after staining. The largest scale platelets, when teased out of the pockets, measured about 0.2 millimeter long. Some were clear and smooth; the first circulus was formed on others. Although some fish such as biook trout form scales first along the posterior ])art of the lateral line (Cooper 1951), a .young lake trout 53 millimeters long had platelets scattered in one or two interrupted rows and in small groups here and tiiere along the anterior end only of the lateral line. The lateral line itself was not in evidence posteriorly. The largest i)latelets on this lake trout were about 0.1 millimeter long and lacked circuli. Probably scales begin to form on lake trout in Lake Superior when the fish are about 50 millimeters long but no histological sections were made to determine this jxiint. It is not known whether young lake trout growing in Lake Michigan develop scales at the same size as those in Lake Superior. One hundred fingerlings, all of the same age but ranging in length from 35 to 85 millimeters, which were reared in the fish hatchery at Charlevoix, Mich., in 1948 and preserved on Septenil)er 17, were examined. The smallest of these lake trout having scales was 47.5 mm. long. This fish liad scales with as many as 4 circuli the full length of tiu' lateral fine. Other specimens 35 to 43 mm. long were without scales and no evidence of a lateral line was seen. Although these young lake trout grew under artificial conditions, development of the scales began at about the same l)0,\ll scah'.s weri' studied ut the sinii' niagnilication (.Xs:t..1). Ulustra- tions (,f I hi' scales have been reduced Xfifi.S. Sec p. 59 fur siRnificanee o( th.' cheek latuled ■'O." of scales). Here, the annulus often is seen dis- tinctly as a ridge on the scale or as a groove on the impression. The groove is well illustrated by the second and third annuli in figure 10, and the third and fourth annuli in figure 9. Another characteristic pattern in the posterior field results at points where circuli of the preceding growing season end and the first circulus of a new season crosses their paths at angles that bring the pattern to a crude V in which the angle of the V points toward the annulus. These V's are in evidence somewhere on nearly every scale, but on the scale shown in figure 7, it is doul)tful whether the fourth annulus would have been located but for the V on the lefthand side, as the annulus is indistinct elsewhere around the scale. The V's are also clearly represented in figure 5 bv tlie second and third annuli, and in figure 8 bv the first, second, and third annuli. Frequently, part of the posterior area of the scale is almost devoid of .sculpturing. Only ragged bits of crooked, discontinuous circuli are scattered about, but even then, circuli extend farther out into this part of the scale at the annulus than between annuli, pointing it out like a crooked finger. In the anterior and lateral fields, three charac- teristics of the pattern of circuli, usually occurring in combination, indicate the location of the annulus. First is the narrowing of the spacing between circuli at the end of a growing season, mentioned earlier and seen in most figures. Usually, in addition, there is a broken circulus here or there along the annulus with another circulus crossing the ends in a "cutting-over" pattern (as in the V formations of the posterior field). The longer circulus which does the cutting-over is the first circulus of the new growth. It is often continuous through the anterior field from the posterior field on one side to the posterior field on the other side of the scale, and may cross or extend partly across the posterior field itself, as shown by the first annulus in figure 12, and by all annuli in figure 11. The third characteristic pattei-n results from the apj)earance of one oi- two very fine, broken lines '* at the annulus. This feature is illustrated by the scale shown in figure 10. Note especially the second and third annuli. The scales shown in figures 5 to 12, also 15A and 16A, are from fish representative of lake trout '• Thes*' do not appear to t'e true circuli. 12 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE FiGt'RE 4. — A scale from a 4-year-olcl lake trout 15.3 inches long, marked in September 1945 and recovered May 7 or 9, 1949, showing the degree to which annuli mark the inner surface of the scales. The outer surface of another scale from the same fish is seen in figure 8. The photograph is a negative of an impression in plastic. AGE DETERMINATION' FROM SCALES OF LAKE TROUT 13 Fkurk f). — Scale (if a lake trout marked in Seiiteiniier I'.Mo and recovered June 11. lOlil. A negative photograph of an impression in plastic. 14 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE FifitiRE G. — Scale of a lake trout 14.8 inches Ions, marked in Seijteniber 1945 and recovered July 8, IIU'.I. The 0- mark and first annulus appear to occur together. A narrow band of new growth is present. presumably of known age. Scales of lake trout whoso age, as rea () — 56 3 16 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE Figure 8.— Scale of a lake trout marked in September 1945 and recovered May 7 or 9, 1949. Note that focus of the scale is located posterior to the center. No new growth. AGE DETERMINATION FROM SCALES OF LAKE TROUT 17 FiciRE 9. — Scale of a lake trout 13.5 inches long, marked in September 1945 and recovered August 13 or 16, 1949. Note that the band of new growth is wider than in figure 7 even though this fish was caught 2 weeks earlier. 18 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE NEW C, , GROWTH-^j NEW GROWTH NEW J^^ GROWTH Figure 10. — Scale of a lake trout 15.9 inches long, marked in September 1945 and recovered April 17, 1950. The 0- mark is more conspicuous than the first annulus on this scale. The band of new growth is narrow, but wider laterally than terminally. AGE DETERMIXATIOX FROM SCALES OF LAKE TROUT 19 Fif.iRE 11. — Scale of a lake trout 15.1 inches long, marked in September 1945 and recovered April 25, 1950. The focus of this scale is located anteriorly. The annuli are indistinct. Such a scale is difficult to read. The band of new growth is narrow. TIME OF ANNULUS FORMATION New gi'owth on lake trout scales is first seen as a narrow, clear band outside a darker band of the closely spaced circuli of "winter growth." In the early part of the season, new growth is too narrow to be distinguished from spacing between winter circtili. For this reason, new growth was i(h'iitified and measured only when it had attained a width greater than that of the spacing between |)rece(Hng circuli and an outer circulus had formed at least part way around the scale. Hence, in this study, the scales had grown an undetermined, though short, time before growth was recorded. One lake trout had some new growth on its scales -laiuiary 19, but no others appeared with new growth until the latter part of .\Iarch. Similarly, a single specimen without new growth was caught September 23, more than a month after new growth was started on the scales of all other fish in the sample. The two aberrant specimens are 20 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE FiniiRE 12. — Scale of a lake trout 16.8 inches long, marked in Septenihor 1945 and recovered April 25, 1950. The 0-mark is more conspicuous than the first annulu.s. The band of new growth is wider than is usually found on scales of the fish caught in April. AGE DETERMINATIOX FROM SCALES OF LAKE TROUT 21 2 3 4 5 6 7 GROWTH Fici-RE 13. — Scale of a lake trout 26.2 inches long with left pectoral fin abnormal allhouKh the type of abnormality was not described. Caught June 13, 1947. If thi.s lake trout had been marked by the removal of the left pectoral fin, it would have been 1 year old, but it is too large for that age, and 8 checks were on the scales. (See text for dis- cussion of the central check). Xew growth was not uniform in width. On this section, new growth appears only in the lower right area. The deformed fin was an abnormality. 22 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 987654 32 1 Figure 14. — Scale of a lake trout 31.8 inches long with left pectoral fin missing; no regeneration. Caught September 10, 1947. Lake trout with left pectoral fin removed were released in September 1946. If marked, this fish should have been 1 year old. Because of its large size, it probably was of more advanced age. Ten checks were read on the scale. (See p. 59 for a discussion of the central check). The band of new growth is wide. The missing fin was an abnormalitv. listed in table 6 because a fin of each appeared to have been clipped and the ai\nuli on the scales seemed well defined. However, the dates on which new growth on the scales was begun are sulli- ciently unusual to throw some doubt on the authen- ticity of the fin-clip and the accuracy of the age determination from the scales. The percentage of lake trout witli new growth on tiieir scales increased slowly through April and May, but rose rapidly through Jinie and Jidy, passed the 50-percent level during the last week of June, and reached the 100-percent level the last half of August (table 6; fig. 17). Al- though the season's growth was detectable on the AGE DETERMINATION FROM SCALES OF LAKE TROUT 23 Fkure 15. — (A) Scale of a lake trout 8.6 inches long, marked in September 1945 and recovered October 8, 1947. The band of new growth is wider than the entire growth zone of the previous year. (B) Scale of a lake trout 10.8 inches long with a right pectoral fin missing; no regeneration. Caught November 4, 1948. Only 3 checks were found on the scales. As lake trout with the right pectoral fin removed were released in September 1945, the scales shovild have had 4 checks, 3 antnili, and 0-mark, if the fish were one of those marked. The missing fin was, therefore, abnormal. scales of some lake trout by the latter part of Marcli, it could not be seen on otliers initil August. The period for the start of new growth, therefore, extends tlu'ough .5 months. Possibly, tiie period wotdd he shorter for groups of fish, all caiigiit from a small, localized area. The present collec- tion of marked lake trout came from contiguous but relatively extensive areas in the nortlieastern part of Lake Michigan. A diversity of environ- mental conditions in various localities, about which there is at ijresent very little information, may cause growth on the scales of local groups of :<78:):if! o— ,^i(; —4 lake trout to begin at different times so that when the groups are combiiu-d, as in the present study, tlie semblance of a long period for tiie begimiing of growth would result. Assuming normal distribution, the combinetl data fit, within the confidence limits at the 5- percent level of probability, a normal cimaulative curve witii tlie (7 = 20 days and the .'iO-percent level on .Time 18. The test used for goodness of fit was tiie Kolmogorov-Smirnov test described by Massey (1951). Whereas tlie .")0-percent level of the theoretical normal po|)uhuion falls on 24 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE Figure 16. — (A) Scale of a lake trout 16.5 inches long, marked in September 1945 and recovered October 5, 1948. Note partial check between the second and third annuli. There was no evidence of a check on the righthand side of the scale. (B) Scale of a lake trout 13.5 inches long with left pectoral fin consisting of 9 twisted rays one-half normal length. Caught December 18, 1948. Four checks appear on the scales. As lake trout with left pectoral fin removed were released in September 1946, the scales should have had 3 checks, 2 annuli, and 0-mark, if the fish were one of those marked. The fin was, therefore, deformed. AGE detp:rmixation from scales of lake trout 25 Table 6. — Progress of anniilus formalion on the marked take trout [Based on rocovcrii's for the calendar years 1947-51 and age groups II-VI. No consistent differences could be detected among age groups In collections from dilTerent years] Date Number without newgrowth Number with new growth Percentage with new growth Date Number without now growth Number with new growth Percentage with new growth Jan 1-15 29 23 g 13 1 20 25 «7 140 55 71 66 1 1 4 3 17 39 24 31 56 0.0 4.2 0.0 0.0 0.0 16.7 10 7 20.2 21.8 30.4 30.4 45.9 July 1-15 48 2 11 104 96 151 fiO 62 47 17 3 3 9 68.4 16-31 93.2 Feb I 15 Aug. 1-15 98.7 16-31 100.0 Mar. 1-15 Sept. 1-15 - 100.0 lfi-31 16-30 97.9 Oct. 1-15. 100.0 10-30 16-31 100. May 1-15 Nov. 1-15 - 100.0 1()-31 16-30 100.0 Dec. 1-15 16-30 16-31 16 100.0 I Sec page 19 for comments on these specimens. 100 t/1 UJ _J < u (/I z o I \- $ o a. o LU Z I t- I (/) Ll ti. o LU z lU o a. LU a 6 23 8 22 8 23 8 23 8 23 8 22 8 23 8 23 8 23 JAN FEB MAR APR MAY JUNE JULY AUG SEPT Figure 17. — Perci'iitanc of marked lake trout curve drawn by inspection. (lowing new growth on their scales. Empirical data indicated by dots 26 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE June 18, the date on which 50 percent of the marked fish had started new growth on the scales was June 26. Within the 5-percent confidence limits for samples of the same size, new growth on the scales of lake trout in other years would be expected to reach tlie 50-percent level during the last 3 weeks of June. New growth may be identified, then, on the scales of individual lake trout in northern Lake Michigan any time be- tween the middle of March and the middle of August, and about 50-percent of the lake trout will show new growth on their scales by the latter part of June. Because of the long time interval in which new growth may begin, the numbers of lake trout with narrow spacing between the circuli at the margin of their scales diminish gradually from January through August and the numbers with wide spac- ing between these circuli increase correspondingly. In July and August some scales, that began growth early in the season, already had a wide band of new growth with narrowing spacing between the circuli near the edge of the scales. The age of unmarked fisli would be difficult to interpret from such scales. Whether the band of growth liad been formed during the current or the previous season would be a matter of the reader's judgment. On most scales from fisli caught at this season, the growth of the current season was narrower than the growth of tlie previous year, but tiiere were exceptions which gave difficulty. The end of the growing season for the scales of lake trout could not be determined definitely from the scales themselves. As new growth on the scales of individual fish in the sample began at different times during the spring and summer, they may also have completed growth at different times. In summer and early fall, scales having wide bands of marginal growth with narrowing spacing between the outer circuli had the appear- ance of completed growtli, but it is not known that additional circuli do not form later in the season. It remains uncertain, therefore, whether the scales of lake trout attain the full growth of a season shortly after the begiiming of growtli or continue to increase in size, however slowly, until time for the next anindus to form. SUPERNUMERARY OR 0-MARK During the first examination of the scales, it was a surprise to discover tliat tlie number of annulus- •like markings observed was almost invariably greater, by one, than the number of years of age indicated by the clipped fin. Upon further inves- tigation, the reason for the discrepancy was found in the interpretation of the mark nearest the focus. Comparisons of lengths at capture of lake trout of a known age group (age-groups II to V) with calculated lengths for the same year of life showed the outermost markings to be annuli. Although no lake trout of age-group I were captured, it is logically to be expected that on their scales, also, the outermost mark would be an annulus, hence that the central check is supernumerary. This check or mark appears to have been formed dur- ing the fall of tlie fish's first year when they were only slightly larger than at the time of planting. The innermost marking on the scales, referred to hereafter as the 0-mark, is interpreted to be a line of demarcation between an initial slow rate of growtli and a later sudden increase in the rate as indicated by a change in spacing of the circuli at this point. The circuli within the central mark are more broken and more closely spaced tlian cir- culi laid down later (figs. 5 and 12). The mark is usually fainter tiian the annular rings on the scales and is not present on the scales of all specimens.'^ Rarely, scales show the central marking so closely approximated to the first an- nulus (figs. 7 and 11) as to suggest that on other scales it might coincide with the annulus and thus be lacking altogether as on the scale in figure 6; a few have it very close to the focus, but for most specimens the inner mark is a little over halfway from the focus to the first annulus. Although this mark is typically indistinct (figs. 5 and 9), it some- times is the most conspicuous mark on the scales (figs. 10 and 12). Such outstanding marks might easily be taken to be first annuli on fish of un- known age unless the reader were expecting to find, and looking for, a mark within the true first aiuiulus. The 0-mark can only be surmised, at this time, to record some drastic change in the young fish's enivronment or habits of life. A possible explana- tion is that the check results from handling (an- aesthetization, removal of fin, transportation) at the time of planting and the change from hatchery to lake environment. In support of this view is " A separatp inner marking was not found on the .scales o( 4 (0.3 iwrcent) of the marked specimens and it is believed the inner mark on these scales coincided with llle first annulus. AGE DETERMIXATION FROM SCALES OF LAKE TROUT 27 the fairly close agreement between the average calculated length of 3.7 inches (range 1.5-5.9) at time of formation of the 0-mark (computed from scale measurements of recovered marked fish) and the average measured length (3.2 inches; range 2.1-4.3) of samples of fingcrlings at time of release into the lake. On the other hand, the examination of scales of lake trout that almost surely were not marked fish (lake trout from northern Lake Michigan that were unreasonably large for the ages indicated by their deformed fins and fish from area 8 that included few, if any, marked fish) suggested strongly that naturally hatched lake trout in Lake Michigan also form a 0-mark. Such a mark could arise, for example, from a change in environmental conditions, a change of diet, or a shift by the fish to different grounds upon attainment of a particu- lar length (about 3.7 inches in the northern part of the lake). The scales of lake trout for which there was disagreement between the age, as indicated by scales and fin, consistently exhibited a first check that resembled in every way the 0-mark on the scales of marked specimens. The scales in figures 13 and 14 were from fish turned in as recoveries of marked lake trout but they were unquestionably from fishes of natural origin. Fish marked in 1946, averaging 3.2 inches long, could not have attained lengths of 26.2 and 31.8 inches before they were caught in 1947. Actually, the scales showed 8 and 10 checks, respectively. The central checks resemble closely the 0-marks of the scales from bona fide recoveries. This is brought out forcefully by figures 15 and 16 in which the lefthand scales are presumably from bona fide recoveries (age read from the scales and age indicated by the deformed fin in agreement); and the righthand scales are probably from natur- ally propagated fish (ages from scales in disagree- ment with age indicated by fin). It is readily apparent that the structure and size of the central areas of these scales are similar. That the central check on the scales of wild- stock lake trout was in fact a 0-mark and not the first annulus was strongly supported by the good agreement between the average calculated lengths of the naturally propagated fish and the marked, liatchery-reared fish at each of the first three checks on the scales. A few lake trout captured by large-mesh nets in northern Ijake Michigan during 1947 could be identified, without question, as wild stock because they were too large to have belonged to any group of marked fish. The calculated lengths of these fish at all three first checks were greater than for the marked lake trout caught in all nets over a period of years, 1947-51 (columns 2 and 4, table 7). The differences were no larger, however, than would be expected from the small number of fish in the sample and from the powerful selective influences that bore on the older age groups of the more recent year classes in the collections. The calculated lengths of the wild stock caught in nets of all mesh sizes '* differed little from tlie marked fish caught in similar nets (columns 2 and 6, table 7). Calcu- lated lengths of wild-stock lake trout caught by all nets in the southern part of the lake were 0.8-1.0 inch shorter at each of the first 3 checks tlian those of wild stock caught in more northern waters (columns 6, 8, table 7). This large dif- ference between calculated lengths of lake trout from the 2 sections of the lake is indicative of the racial separation of the 2 pojjulations. '* This group of lake trout incluiles. in addition to those positively Identified as wild stock, other lake trout for wtiich the age read from the scales differed from that indicated by the deformeil fin. Evidence is i)resented later to show tliat most, if not all, of these fisli were also wild stock. Table 7. — Calmlaled total lengths (inches) and increments of growth in length of marked lake trout recaptured in northern Lake Michigan and of naturally propagated fish from northern and southern Lake Michigan year classes combined Unmarked lake trout Northern areas 1-6, from all nets Northern -areas 1-6 Southern-area 8 Check or annulus From large-mesh nets From all nets From all nets Length Increment Length Increment length Increment Length Increment 3.7 5.9 8.7 4.0 6.9 10.0 3.5 6.6 8.3 2.7 4.8 7.3 1 2.2 2.8 2.9 3.1 2.i 2.7 2.1 2 2.5 1,318 M6 99 102 .\ge groups in sample n- VI III -IX 11- IX II-'' k'lll ' The marked lake trout averaged 3.2 inches long at time of planting. ' This total includes 9 fish obviously too large for their supposed age (see p. 30) and also 7 that could not be assigned to a particular planting (more thaii one fin deformed or the deformed fin not one used as a mark), but wtiicti were too large to have been from any of the three plantings. .\11 fish weri' caught In 194i . 28 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE Discrepancies between increments of growth were also small. At the second check the differ- ence was 0.1 inch between marked and unmarked fish from all nets in areas 1-6, but was nil between unmarked or wild stocks from the northern and southern parts of the lake. At the third check the increment of growth of the unmarked fish in areas 1-6 was 0.1 inch smaller than that of the marked fish from the same areas and 0.2 inch larger than that of the unmarked fish in area 8. With regard to the central check on the scales of the naturally reared lake trout, two assumptions are possible. First, that these fish did in fact form a 0-mark during their first growing season; under this assumption these data exhibit no particular conflict with those for planted lake trout. Second, it may be assumed that naturally reared lake trout do not complete a 0-mark, and hence that the calculated lengths for the first three checks on the scales describe the fish at completion of their first, second, and third growing seasons. A corollary to this thesis, namely, that the average length of the unmarked, wild fish from all nets in areas 1-6, at the end of their first year (3.5 inches), was about the same as that of the marked, hatchery fish at formation of the 0-mark (3.7 inches), might be accepted without mis- givings as the hatchery and naturally propagated lake trout spent much of their first year in different environments. If this corollary is accepted, however, it follows that the increment of growth in length of the wild stock in northern Lake Michigan during their second growing season would be only 2.1 inches which is considerably less than the growth indicated for this group during either the first or third (2.7 inches) years. A growth of 2.1 inches the second year would be 0.7 inch less than the growth made in the same environment by the hatchery fish in their second year and 0.6 inch less than the growth made by the marked liatchery fish between their introduc- tion into the lake in September at a length of 3.2 inches and formation of the first annulus when they were 5.9 inches long. The growth made by the wild stock between formation of tlie first two checks on their scales, nevertheless, was very nearly the same as that made by the marked fish between formation of the 0-mark and the first annulus. It would be expected that the wild stock would grow at about the same rate as the introiluced fish after Sep- tember, but if they did, and the first check on the scales were the first annulus, they could not have grown any the fore part of the season. The length of the wild stock at the end of the second year would be 5.6 inches or 0.3 inch shorter than the marked stock at the end of their firs t year and 3 . 1 inches shorter than the marked fish at the end of their second year. To justify this relationship, it isneces- sary to assume that the wild stock grew erratically during their first or second year. The rates of growth in later years were about the same for the marked and unmarked lake trout. Although it cannot be stated categorically that the central check on the scales of the unmarked fish was not the first annulus, neither does it seem reasonable to assume that it is. The evidence strongly favors the belief that the first check on the scales of the naturally propagated lake trout is a 0-mark formed during the first growing season. This view is supported further by the appearance of the check itself (pattern, and location on the scales). See figures 15 and 16. The contribution of data on lake trout from southern Lake Michigan to the problem of the 0-mark is greatly limited by the lack of recoveries of planted fish from this area for comparison with the wild stock. Nevertheless, the much smaller increment of growth before formation of the first check on the scales of lake trout in southern than in northern waters makes it difficult to assume that the 0-mark of these naturally propagated fish is a first annulus. If this assumption is made, it is necessary to believe that these fish were only 4.8 inches long at the end of two full growing seasons or 1.1 inches shorter than tlie marked fish from northern Lake Michigan at the end of one year (5.9 inches). Alternatively, if it is assumed that the first check is a 0-mark, the calculated length at that point is somewhat smaller than that for the northern fish at formation of this check. vSubsequent growtli is only slightly less for the soutiiern than the northern fish. This growth pattern follows closely that of the marked fish. If the hypothesis, that most or all naturally reared lake trout do form a 0-mark on their scales during their first growing season, is ac- cepted, the question then arises as to the extent of error that this structure might introduce into the work of a competent and careful scale reader who is not aware of its existence. The only objective information on this point comes from AGE DETEKMIXATIOX FROM SCALES OF LAKE TROUT 29 records of culculatccl lengths for 97 lake trout captured in large-mesh gill nets off Montague, Mich., October 1, 1947 (Van Oosten 1950). The scales of these fish were read by Dr. Frank W. Jobes who did not record having observed the 0-mark. The calculated lengths from 82 of the fish in the year classes 1939-43 yielded an average length of 5.1 inches at the end of the first year of life. This average is Ijctwecn (1.5 inches higher and 1.0 inch lower than) the averages 3.6 and 6.1 inches obtained in tlie present study for the lengths at formation of tiie 0-mark and the first annulus, respectively, from 17 lake trout of the same year classes from southern I..ake Michigan (off South Haven in area 8) caught in the same year and in nets of the same mesh size (table 23). These differences suggest that on some scales Dr. Jobes may have measured the first aniuilus to the 0-mark rather than to the first annulus. How- ever, the calculated lengths " for the later years of life of the lake trout from Montague and South Haven were close enougli to indicate good agreement on the assessment of age. From tliese data, it appears tlial without a knowledge of the 0-mark, errors in measuring to the first annulus of lake trout scales, due to mis- interpretation of the central check, might be numerous enough to bias seriously an estimate of the first-year growth of I^ake Michigan lake trout, but errors of age determination would be few. AGREEMENT BETWEEN FIRST AND SECOND READINGS The two readings of lake trout scales, mentioned previously, were made on the scales of all fish in the collection. No samples were discarded, how- ever difficult to read. The second series of read- ings was begun several months after the first was completed and, for each fish, a second scale was read and measured, after comparison with the other mounted scales in the sample. The two readings agreed on age for 96.8 percent of the fish. Errors of interpretation, not involving change in age, reduced agreement to 91.4 percent of the specimens. Because of experience gained during the first reading, and standardization of proce- dures, the second reading disclosed errors in the earlier work as shown in table 8. Many of the disagreements resulted from the omission of a '• Sums of the incrcmfnts of growtfi. Those for the lake trout from .Mon- tapue. Mich., were obtained from the puhlislu'd data. measurement of the central or 0-mark, and the mistaken location of annuli. However, there were also disagreements on the number of annuli. The number of annuli located during the second reading varied from that recorded during the first reading for 45 (3.2 percent) of the fisii as follows: 1 annulus more for 18 fish, 1 annulus less for 24 fish, 2 less for 2 fish, and 3 less for 1 fish. The differences in percentage of such disagreements among the data for tlu' tliree plantings were not large. Disagreements in measurement, not re- sulting in change of age, occurred for scales of 76 (5.4 percent) of the fish. T.\BLE 8. — Comparison of first and second readings by the same person, of scales from the '^marked" lake trout Item Year of planting Totals 1944 1945 1946 57 1,077 271 1,405 Differences from first to second reading Rpsultinp in change of ape: 14 13 2 4 9 18 2 24 2 1 Total 3 5.3 29 2.7 13 4.8 45 Percentage 3.2 Not resulting in change of age; .\ssumption of marginal growth in 4 10 45 4 1 9 8 Current season's marginal growth 1 2 12 Age same but one or more annuli 56 3 5.3 59 5.5 14 5.2 76 5.4 fi 10.5 88 8.2 27 10.0 121 8.6 Disagreements in readings due to omission of the central check at the first reading were recorded, but were not considered to be errors in reading because the importance of measuring the 0-mark was not fully understood at the beginning of the first reading. Measurements of tlie central mark had been taken commonly, liowever, when loca- tion of the first annulus was math' easier In- defi- nitely locating the central check. The scales of some lake trout present such prob- lems of interpretation that readings made at differ- ent times are likely to disagree. Much of this un- certainty is dispelled by long familiarity with scales from fish of known age. Most readers dis- card the more didicult scales (usually about 5 per- cent of the total) as unreadable. U this practice liad been followed in the present study, some of 30 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE the (lisajiroemoiits bctwopii readings miglit liave been eliminated. AGREEMENT BETWEEN AGES READ FROM SCALES AND AGES FIXED BY DEFORMED FINS The final readings of the lake trout scales agreed witli the supposed ages of the fish for 1,319 of the 1,405 or 93.9 pereent of the specimens from nor- tliern I^ake Michigan. The presumed age is fk'- termined as the time between tiie date of capture and the year tlie fish would have been liatclied if the damaged fin were a true mark of identification. Detailed information is given in tal)le 9 for the 86 lake trout for whicii the supposed ages and the ages as read from the scales were in disagreement. Of this numlier, 9 fisii (indicated by asterisks in the talile) were so large in relation to their sup- posed age tiiat it may be assumed with confidence that they were unmarked fisii with malformed fins. No de])en(lal)U' objective standard was found from which to judge wlietlier or not the re- maining 77 lake trout were iiona fide recoveries of marked lake trout. They must accordingly be classed collectively as of "uncertain status." Data presented in a later section, however, give evidence that a large percentage of these fish liad not been marked. A summary of the discrepancies in age with respect to the degree of divergence (including the 9 fish designated in table 9 as too large for their supposed age) is given in table 10. Disagree- ments on age were mostly of 1 year (68.6 percent): but were of 2 years for 18.6 percent and more than 2 years for 12.8 percent. T.\BLE 9. — Inforiiintion on SfS lake trout from northern Lake Michigan for which aqe indicated by the mark did not agree with age read from the scales [Asterisks designate fish that obviously were too large in relation to their supposed ages to have been bona fide recoveries of marked fish] T.\Bi,E 0. — Information on 86 lake trout from northern Lake Michigan for which age indicated hi/ the mark did not agree with age read from the scales — Continued Total length (inches) Sup- posed age Age read from scales ml?ked Condition of an 31.8' 12.3'.. 21.2' 20.0' 14.H* _. 13.3* 12.7 __ 20.0* __ 19.0* 16.5' 12.0 22.0 21.5 20.0 20.0 17.6 14.1 1 1 2 2 2 2 2 2 2 2 2 3 3 3 I 3 9 3 4 5 3 3 5 6 7 r, 3 5 4 6 5 5 1946 1946 1945 1945 1945 1945 1945 1946 1946 1946 1946 1944 1944 1944 1944 1944 1944 No regeneration, or fin missing. ?3 normal length. No informLition. Do. yi normal length, rays twisted. Short stub, 2 twisted rays. ]r'i normal length. .\o information. Small stub. No information. Uo. Do. Do. Adipo.se missing, dorsal normal. Do. Do. Do. Total length (inches) 17.5 1.5.4 14.8 13.3 11.7 11.5 11.2 10.8 10.0 9.5 22.0 lfi.8 15.9 12.7 12.7 12.1 12.1 11.9 11.6 11.3 11.0 14.1 21.8 20.5 20.0 19.3. 18.2. 18.0 16.1 16.0 15.6. 14.7 13.9 12.5. 12.1. 11.7. 9.7 18.0. 14.9. 14.3. 13.4. 13.1. 12.0. 17.3. 14.4 13.7, 13.0. 12.S. 11.8. 11.8. 20.0. 19.4. 19.0. 18.8. 18.7. 18.6. 18.0. 17.0. 17.0. 16.3. 14.0. 13.8. 12.4. 12.2. 11.3. 11.2. 10.8. 13.4- 13.0- Sup- posed age Age read from Year marked' Condition of fin 1945 1945 1945 1945 1945 1945 1945 1945 1945 2 1945 5 1946 4 1946 5 1946 4 1946 4 1946 4 1940 4 1946 4 1946 5 1946 2 1946 4 1946 3 1944 5 1945 7 1945 5 1945 6 1945 6 1945 1945 3 1945 5 1945 5 1945 5 1945 5 1946 5 1945 3 1945 :i 1945 2 1945 5 1946 5 1946 5 1946 5 1946 5 1946 5 1946 6 1944 4 1944 4 1944 4 1944 3 1944 4 1944 4 1944 6 1946 6 1946 6 1945 6 1945 6 1945 6 1945 6 1946 fi 1945 4 1945 6 1945 4 1945 3 1945 1945 4 1945 4 1945 4 1945 3 1946 6 1946 4 1945 No regeneration, or fin missinfr. Do. Do. Do. Do. Do. Do. Do. Little regeneration. No information. Fin scar not seen in Ann Arhor. No regeneration, or fin missing. Do, l^ normal length, 8 rays. '/4 normal length, 1 curved ray. ^ii normal length, 10 twisted rays. \i> normal length, rays twisted. !^ normal length, 4 twisted rays. Ml normal length, fi twisted rays. H normal Irntzth. 12 twisted rays. No regt'niTation. or fin missing. H inch long, 1 twisted ray. Adipose missing, 4 rays in dorsal. 34 normal length, some rays fused and curved. 34 normal length, fi twisted rays. S rays. Xo regeneration, or fin missing. H normal length, 4 rays. ^4 normal length, H rays, Xo regeneration, oi' fin missing. Do. Do. Almost normal length, 7 rays. H normal length, 9 twisted rays. \i normal length, ray^ twisted. No regeneration, or fin missing. V-i inch long, 7 rays. \\ inch long, 1 curved ray. X^o regeneration, or fin missing. ^i normal length, H rays. \i normal length, fi rays. X'o regeneration, or fin missing. Do. H inch long. 2 twisted rays. Adipose missing, dorsal normal length but with all rays crooked ^6 distance from back. Adipose torn, dorsal normal. Do. Do. Adipose missing, dorsal normal. Adiposi- small, dorsal normal. Adipose missing, dorsal normal. J.4 inch long. 2 twisted rays. i^ normal length, b rays, Xo regeneration, or fin missing. Do. Do. Do. },-2 inch long, 2 twisted rays, i.^ normal length. ^ rays. No regeneration,- or fin missing H normal length, 2 rays. ^1 normal length, rays broken. Normal length. H norma! length, 4 curved rays. ^4 normal length, 8 normal rays, fi twisted ravs. 34 normal Irngth. 14 iwisted rays. ^4 normal length. 9 rays, ^^ normal l*'ngth. 3 twisted rays. ^^ normal length. 10 rays. 3i norma! length, 9 twisted rays. Table 10. — Smriwary of (he extent of disagreements on lake trout showing discrepancies between supposed ages and those read front the scales Areas 1-fi .\ge discrepancy Number of fish Percentage .59 16 11 68.6 2 years 18.6 >2 years 12.8 AGE DETKRMIXATIOX FROM SCALES OF LAKE TROUT 31 FACTORS OF DISAGREEMENT Disagroempiits hctwocn ajres as read from scales and supposod ages can arise from misinterpreta- tion of the scales from bona fide recovei-ies, and also from the inclusion in tlie sampl(> of lake trout that had not been marked. Both types of errors may be represented in the disagi-eements discussed in the precedino; section. Although the relative importance of these factors cannot be estimated closely, the data do provide some instructive in- formation in tlie matter. Errors of Reading Errors of reading may originate in tlie inter- pretation of scale patterns which, properlv diag- nosed, could lead to a correct determination of the age of the fish. Errors may arise also from defective scales, that is, scales that failed to form certain aimuli, developed accessory checks indis- tinguishable from amudi, or had a pattern so diffuse that any reading is questionable. As was pointed out earlier, the present collection certaiidy contained some lake trout that were not recoveries from plantings of fin-clipped fish. It is impossible, therefore, to attribute any individual disagreement strictly to error on the part of the scah> reader. It is possible, however, to gain a general idea of tlie clarity and dependability of scale patterns from the examination of a large series of scales, a high percentage of whicli must be from bona fide recoveries of planted fish, even thougii the status of an uidividual specimen must be recognized as uncertain. Careful study of the hundreds of scales from which readings agreed with supposed age led to the conclusion that over the age-span represented, the markings were almost always clear, and that failure to form an aiumlus must be rare. Some annuli were extremely faint, espe- cially in the posterior field but faint year-marks usually could be detected in the lateral fields. The presence of an occasional indistinct annidus does, nevertiieless, indicate the possibility of others so weak as to be overlooked. Accessory checks between atniuli, other than the 0-mark discussed in the preceding section, were not connnon and when present caused little trouble because they rarely, if ever, extended completely around the scale. Another factor which may iiave been a source of some error is the int.'rpretation of marginal growth. Dining th(> period of aiuiulus formation it is occasioiuilly didicult to decide whetlu-r the marginal band rei)resents completed growth of the previous year or rapid growth of the current season. Inclusion of Unmarked Fish With Abnormal Fins Overwhelming evidence was |)resented earlier that the "recoveries" from southern Lake Michi- gan (area 8) included few, if any, marked lake trout. Since there is no reason to believe that the development of a])norniaI fins among naturally propagated fish is exclusively a property of tin- stock of lake trout in southern Lake Michigan, it was to be anticipated that the recoveries from northern Lake Michigan, though principally marked fish of Imtchery origin, woulil also iiu'lude some naturally hatciied lake trout (and possibly some unmarked hatchery-reared lake trout that tleveloj)ed abnormal fins).-" Relation of disagreements to appearance of the fin If data on the "extent of regeneration" of the fins of lake trout from area 8 (tal)les 3 aiul 4) are typical for abnormal fins on wild fish, then, in samples from northern Lake Michigan (areas 1-6), the great majority of fish with fewer than 5 rays regenerated or with fins less than y, normal length would be bona fide recoveries of marked speci- mens, whereas most unmarked fisli with abnormal fins would appear in the group sliowitig greater regeneration. If these conchisions are valid and if the collection of lake trout from northern Lake Micliigan contains appreciable numbers of wild fish, a correlation should l)e found between the extent of regeneration and tlie percentage of dis- agreement l)etween supjjosed ages and ages read from scales. Tills expectation is met l)y the data of table 11, for the lowest percentage disagreenu'iit (3.8 per- cent) occurred among fish with fewer tiian .5 fin rays regenerated less than half normal length. For the other three groups in the nuiin body of the table the percentages ranged from (5.3 (trout with fewer than r, fin rays regenerated but iialf normal length or longer) to 10.7 (fish with fins less than half normal length but having 5 or more fin rays re generated). The value of 6.9 percent ■" Allhough the pvmTitaBi' of wild-stuck hiko Iiout with alinorllKil fins is smiill, llir total niinihiT irport.-il hy fishmiii'ii can he con.siilcrahlc when all catches arc hi'Inc .scnititlizcil for dcfornicil fins. The perccntaRC of hatchery fish with ahnormal fins is also low. Dr. I'aul K.schincycr. who has hcon in charge of fin-clip|iin(! o|)eraIions at the fnitcd Stales Kish and Wildlife Service Fish Hatchery near Charlc'voix, .Mich,, several seiisons. states that an occasional finserlinc lake trout reared in the hatchery has an accrs-sory fin hut very few finperlings have deformed fins. 32 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE for trout with more than 5 fin rays at least half normal length offers a slight inconsistency, since, on the basis of the assumptions made, this per- centage should have been the largest. Table 11. — Relation of extent of the regeneration of pectoral fins, expressed in terms of number of regenerated rays and length {fraction of normal) to percentage disagreement between ages as determined from scales and as indicated by deformed fins Length of fin Less than half normal. Half normal or longer. All lengths Item Xiiiiibcr tif fish |-j\uiiihiT i)f 60 3 8.3 3 100.0 Total or average . . 36 5 13.9 1948: <20 123 61.8 3 2.4 20-40 61 30.7 6 9.8 40-60 15 7.5 1 6.7 >60 Total or average. . . 199 10 6.0 1949: <20 -- 91 17.2 3 3.3 20-10 -- 251 47.5 2 0.8 40-fiO— 156 29.6 3 1.9 >60 30 5.7 4 13 3 Total or average . . . 528 12 2.3 19.M): <20 59 23.4 2 3.4 20-tO 48 19.0 4 8 3 40-60 138 54.8 8 .5.8 >60 7 2.8 3 42.8 Total or average- - - 252 17 6.7 \m\: <20 0.0 0.0 20-40 5 18.6 ao 40-60 . . . 9 13 33.3 48.2 1 8 11. 1 >60 61.6 Total or average. . - 27 9 33.3 ' Some lake trout were omitted from this table because the description of the locality of capture was indefinite. 2 All disagreements were on lake trout captured along the north and east shores of Lake Michigan, areas 2, 3, 5, and 6. There were no disagreements on those captured in areas 1 and 4. The sequence of changes through the years fol- lowed the expected pattern. The percentage dis- agreement (between supposed age and age read from scales) was relatively high (13.9 percent) in 1947 when only 36 recoveries were made. As the number of recoveries rose to a maximum of 528 in 1949, the percentage disagreement dechned to AGE DETERMINATION FROM SCALES OF LAKE TROUT 33 a miiiiinuin of 2:.i. Decreases in tlu- luimber of recoveries to 2.')2 fish in 1950 and a mere 27 in 1951 were accompanied hy increases in percentage dis- agreement to 6.7 and 33.3 percent, respectively. The onU-r with respect to the size of the annual total number of lake trout recaptured was practi- cally tlie reverse of the order of the percentage disagreements. The one exception was between ranks 2 and 3 where the difTerences in percentage disagreement were small but sufficient to reverse the order of the ranking as shown: Year Number of fish Rank Percentage disagree- ments Rank 1949 _ 528 252 199 36 27 1 2 3 4 5 2.3 6.7 5.0 13.9 33.3 5 1950 3 1948 - 4 1947 2 1951 1 Still another significant feature of the annual totals is the limited range in the number of dis- agreements (from 5 in 1947 to 17 in 1950). The indicated variability is much below that of total recaptures for corresponding years. For example, from 1947 to 1949 the catch of fish with deformed fins increased 14.7 times but the number of dis- agreements increased only 2.4 times. Thus it ap- pears that the number of disagreements tended to fluctuate about a fairly stable level and to be rela- tively independent of the number of recaptures of marked fish. This relation is precisely the one which should obtain if a liigh percentage of the disagreements were caused by the presence of un- marked fisli. The data on tlie relation between locality of capture and percentage agreement within and between calendar years exhibit certain incoti- sistencies most of which can be attributed to tlic small numbers of fish in some entries. D(>finite trends can l)e detected, nevertheless. It is seen, for example, that tlie percentage disagreement between supposed ages and ages read from scales was invariably nil or small (0.0 to 3.4 percent) for lake trout recaptured within 20 miles of tlie point of release. The percentages were large, on the other hand, foi' trout recaptured more than 60 miles from the locality of planting. Only in 1949, when 13.3 percent of the fish were in disagreement on age, was there evidence of consideiai)le numbers of bona fide marked fish in this aiea. In the re- maining 3 years in which recaptures were re[)orted from distances greater than 60 miles, the per- centages ran from 42.8 to 100.0 (numbers of fish were small but the figures probably are significant because of consistently high values). For lake trout captured at tlie two intermediate distances, the percentage disagreement was nil at 20 to 40 miles in 1947 and 1951, but only 5 fish were reported each year. The remaining records for fish captured at 20 to 40 or 40 to 60 miles indi- cate a general inverse relationship between per- centage disagreement and number of lake trout reported. In the largest sample, 251 fish at 20 to 40 miles in 1949, the percentage disagreement was only 0.8; the two samples in the range of 100 to 200 fish had percentages of 1.9 and 5.8; and the four samples containing fewer than 100 fish had per- centages ranging from 6.7 to 22.2. The data of table 12, taken as a whole, lend strong additional support to tlie belief that a con- siderable part of the disagreements between sup- posed ages and ages read from the scales can be attributed to the presence in the sample of un- marked lake trout with abnormal fins. Relation of disagreements to size of fish It was stated in an earlier section that 9 of the 86 lake trout, for whicli the supposed ages and ages read from scales did not agree, were too large for their supposed age and lience almost certainly were not recoveries of marked fish, but merely had ab- normal fins (these fish are designated by asterisks in table 9). The basis for this conclusion is to be found in the length-frequency distributions of table 13. The 9 fish include 2 members of age-group I (marked lake trout of this age seemingly were still too small to be captured in commercial nets) and the 7 lake trout of age-group II that lay well outside the range of length for lake trout of the same age for which scale reading and supposed age agreed. For the remaining fish, length does not appear to offer a safe criterion for judgment as to whether any particular individual in a "no" column was or was not a marked fish. The frequencies and mean lengths for the paired groupings are so different, however, as to leave no doubt that the lake trout, for which supposed age and age as read did not agree, included considerable numbers of un- marked fish. Despite the wide ranges in length of individual age groups and the extensive overlap between successive age groups, the distribution of 34 FISHERY BITLLETIN OF THE FISH AND WILDLIFE SERVICE Table 13. — Length-frequency distribution of "marked" lake trout at capture, in age groups indicated by deformed or missing fin (all year classes combined) [Fish in "yes" column of cacli ago group are those tor which age read from scales agreed with age indicated by abnormal fin. and fish in the "no" column are those for « hich ages disagreed. Total lengths in inches] Age group Total length I II III IV V 1 No = Yes No Yes No Yes No Yes No 7 7 4 1 7 5 7 9 8 0-8 4 4 7 4 2 7 6 3 4 1 1 8 5-8 9 1 1 1 4 2 12 28 33 31 39 31 27 20 8 9 5 2 2 1 "T ! 1 ...... 2 7 19 44 84 74 84 HI 90 68 56 26 27 18 .8 3 3 3 1 1 1 10 0-10.4 . . . 2 10 5 10 9 1 11 0-11.4 T 2 1 2 1 2 2 ...... 2 ...... ...... ...... 1 ...... 3 2 6 4 10 5 18 15 24 41 23 31 26 17 14 14 10 5 6 2 11 5-11 9 2 12.0-12.4 --. 12 5-12.9 1 2 1 13.0-13.4 2 13 5-13 9 2 14 0-14.4 2 14.5-14.9 1 15 0-15 4 1 15.5-15.9 16 0-16 4 3 16 5-16 9 1 1 17.0-17.4 3 17 5-17 9 2 1 18 5 18 9 3 19 0-19 4 1 2 20 0-20.4 3 1 2 1 on "i 20 9 1 2 2 1 21 5-21 9 1 2 1 31.5-31.9 1 Number Mean length.-. 2 22 39 10.0 10 17.0 255 12.8 27 14.5 732 14.3 22 15.5 280 15.9 25 15.0 I Later age groups not included because the number of fish in each was too small to Yield useful information. ' No fish were captured for which the age read from the scales agreed with this supposed age. the lengtlis and the progressive shift of modes and means of fish in the "Yes" cohimns are much as would be expected. The frequencies in the "no" columns do not exhibit a similarly consistent rela- tionship. They show a random scatter greater than that which can be ascribed to the small num- bers of fish. Modes are lacking, and the means give no indication of the progressive increase in size that should accompany increase in age. The dif- ferences between the two groups with respect to indicated growth is demonstrated by the summary in table 14. Here, as was true for fish from south- ern Lake Michigan, the lake trout for which there was disagreement on age present the ridiculous spectacle of diminishing length with increase in age. A high percentage of tliem obviously could not have been from plantings of marked fingerlings. Another approach to the question of the presence of unmarked lake trout in the samples lies in the comparison of the growth of lake trout for which there was agreement on age with the growth of thosef or which there was not agreement on age. In this comparison it was assumed that none of the lake trout for which there was disagreement were marked fish and that the scales rather than fin abnormalities offer the correct estimate of age. Table 15, which gives the result of this compari- son, is so arranged that the vertical columns give the average lengths at ages indicated by abnormal fins and diagonal rows (from upper left to lower right) contain a series of estimates of the length of lake trout of the same age, as read from the scales. As would be anticipated, if the readings are correct, the lake trout with agreement on age were shorter than those whose ages, read from the scales, were one or more years older than the ages indicated by the deformed fins. Conversely, the lake trout with agreement on age were larger than others whose ages were read one or more years younger than the ages indicated by the fins. In general, the magnitude of this difference in lengths was progressively greater with each in- crease in tiie number of years of disagreement between the supposed age of the fish and the age read from the scales. Despite the considerable variability expected because of the small numbers of fish in some samples and the known large range of lengths within age groups, the means in each diagonal, in the main, fluctuate normally about the average length determined for lake trout for whicli ages from scales and fin marks agreed. Data in summarj- table 16 support the conten- tion that lengths of age groups determined by Table 14. — Comparison of average lengths of lake trout, for which the ages as indicated by scales and fins were the same, with average lengths as indicated by abnormal fins of lake trout for which ages indicated by fins and scales were different [Data from table 13. Number of fish in parentheses] Total length (inches) Age group Scales and fins in agreement Scales and fins not in agreement 22.0 I (2) 17.0 (10) 14.5 (27) 15.5 (22) 15.0 (25) II 1 10.0 \ (39) / 12.8 \ (255) / 14.3 \ (732) / 15.9 \ (280) HI IV V AGE DETKRMIXATIOX FROM SCALES OF L,\KE TROUT 35 Table 15. — Comparison of the average lengths of lake Iroiil whose scale readings disagreed with their supposed age uith the average lengths of lake trout for which the reading agreed with the supposed age ' (In all readings, It was assumed that the central check was a O-mark] Departure of age read from expected age 5 yean; more: Age from scales.. .\verage length.. Number of fish_. 4 years more: .\gi' from scales.. .\vorape length _. Number of fish.. 3 years more: .\ge from scales. .\verage length.. Number of fish., 2 years more; .\ge from scales,, .\verage length.. Number offish.. 1 year more: .\ge from scales. .\verage length. Number of fish. .\s expected: .\ge from scales. .\verage length. Number of fish. 1 year less: Age from scales. .\verage length. Number of fish. 2 years less: .\ge from scales. .\verage length. Number of fish. 3 years less: .^ge from scales. Average length. Number of fish. Age indicated by fln mark reported III 12.3 1 I '5.6 1,319 VII 19.0 1 VI 18.2 2 V 16.4 2 IV 21.2 1 III 13.4 3 II 10.0 39 HI IV VII 20.0 1 VI 20.0 1 V 16.1 6 IV 13.4 15 III 12.8 255 II 10.5 3 VII 19.2 2 VI 18.8 2 V 15.4 13 IV 14.3 732 III 13.5 4 II 9.3 I VII 22.0 1 VI 17.8 11 V 15.8 280 IV 13.0 10 III 12.5 3 II 12.4 1 VI VI 15.6 13 IV 13,0 1 ' In addition to the fish listed in the table, the collection contained 1 lake trout. 31,8 inches long, which, according to the fin. should have belonged to age-group I but the scales indicated it to be a member of age-group IX. • A mean calculated length bii.'^ed on all lake trout for which ages from scales and fin marks agreed. The samples contained no fisli whose scales indicated that they belonged to age-group I. scale readings give a reasonable estimate on growtli of tlie lake trout for which ages from scales and fins disagreed. In tliis table age groups, as established from the scales, have been combined regardless of discrepancies between supposed age and age as read. For age groups II to V, the differences in average lengths between the lake trout with and without agreement on age fell within the range of 0.1 inch (age-group V) to 0.8 inch (age-group IV). The difference was fairly large (2. .5 inches) for age-group VI, but here the average length for trout with agreement (15.6 inches) must be viewed with skepticism as it was 0.2 inch below the mean lengtli for age-group V (15.8 inches). Despite this discrepancy, the data, as a whole, show that the scale readings gave reasonable estimates of the growth of tlie 86 fish with disagreement on age, and hence provide still further evidence of a high percentage of unmarked lake trout among them. Table 16. — Comparison of average lengths of lake trout for which the ages as indicated by scales and fins were the same, with average lengths as indicated by scale readings for the 86 lake trout foi which ages indicated by fins and scales were different [Data from table 15. Number of fish in parentheses.) Total length (Inches) Age group Scales and Sns in agreement Scales and flns not in agreement II f 10.0 \ (39) 10.6 (5) III. 12.8 (255) 14.3 (732) 15.8 (280) 1 15.6 (13) 13.1 (11) 13.5 (27) 15.7 (21) 18.1 (16) ' This low figure is probably due to selective destruction of the lake trout population in Lake Michigan. CONCLUSIONS AS TO THE DEPENDABILITY OF SCALE READINGS The study of tlie scales of lake trout presumably of known age has proved scale readings to be highly dependable over the age span represented in the sample. In the original collection of 1,405 recaptured lake trout from northern Lake Michi- gan, ages as read from scales agreed with ages as indicated by fin marks for l,.'n9 or 9:5.9 percent of the individuals. The actual degree of de- pendability is much greater, however, than this percentage suggests. The evidence is strong that the 86 fish, for which ages were in disagreement, actually included many unmarked individuals on wliich fin development had been abnormal. Nine lake trout could be designated with confidence as "unmarked" because of their unreasonably large size in relation to their supposed age. Criteria were lacking for an objective decision as to whether any one individual among the remaining 77 fish could have been a bona fide recovery, but a series of analyses on the reflation of the disagreements to appearance of the deformed fins, year and locality of recapture, size and growth of fish yielded con- vincing evidence of tlie presence of considerable numbers of unmarked lake trout. Although an exact figure can not be given, it can be stated with confidence that, had the original sample been composed entirely of recaptures from the three plantings of marked fish, the agreement between supposed ages and ages read from the scales would have been well above 95 percent. The O-mark, a check in the field of first-year growtli, was present on the scales of nearly all 36 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE marked lake trout recaptured and, according to the best available evidence, was also a charac- teristic of the scales of most wild fish. It should be emphasized that, dependable as lake trout scales may be as indicators of age, thej- are not read easily. Considerable experience is required before a reader's interpretation of the scale pattern becomes highlj' reliable. Even the experienced reader can do accurate work only if the scale preparations are clear and they are studied carefully with the aid of the best optical equipment. GROWTH OF MARKED LAKE TROUT The study of the growth of marked lake trout is based principally on the 1,319 specimens for which the age as read from the scales agreed with the supposed age. This restriction excludes any bona fide recaptures for which errors were made in scale readings. The 1,319 fish may include a few unmarked fish with abnormal fins that hap- pened to be of the correct age at capture. There is no reason to believe, however, that the number in either of the groups is large; the restricted sample, therefore, may safely be presumed to consist almost entirely of marked fish and also to include nearly all of the true recoveries. Measurements of the marked lake trout were made in Ann Arbor before the fish were preserved but after they had been shipped in ice from the port where they were landed. Although most of the fish were in good condition upon arrival, a few were in advanced stages of decomposition so that length and weight measurements could not be determined accurately. Such fish have been ex- cluded from tables and calculations for which those measurements are requisite. In some tables the total number of fish was further reduced by dropping from consideration the older age groups which were poorly represented. More lengths than weights were obtained because some of the lake trout were dressed (gills and viscera removed) upon arrival in Aim Arbor. LENGTH-WEIGHT RELATION The commonly accepted formula expressing the length-weight relation in fishes is: W=cL" or log M'=log c+n log L where Ii'= weight L = total length and c and « = constants As tlie measurements of length antl weight alike are subject to error, a method developed by Bartlett (1949) was used in fitting a line to the logarithms of individual lengths and weights of 1,197 lake trout ^' from northern Lake Micliigan. The resulting estimate of the relation between woiglit in ounces and total length in inches was: log ir= -2. 4698-1-3.1125 log L The value of 3.1125 for n (which measures the relative rates of increase of weight and length) shows that in these lake trout the weight increased somewhat faster than the cube of the length. In other words, the body form became more robust as the fish grew longer. The departure of the lengtli-weight relation- ship of the lake trout of northern Lake Micliigan from the "cube law" probably was significant. The 5-percent confidence interval of the true slope /3 with ^ = 1.962 for 1,195 degrees of freedom, when calculated by Bartlett's method was 3.13718±0.90129. At the same level of signifi- cance, the least squares method gave 6xy = 3.08414 ±0.04332. Comparisons between empirical weights and tlieoretical weights (as computed from the length- weight equation) are to be found in table 17 and figure 18; the straight line of figure 18 is a graph of the equation. Because talile 17 contains actual and computed values of both length and weight, an explanation of the arrangement may be lielpful. The first row of figures in the left section, for example, states first that the single lake trout 7.2 inches long had a weight of 1.2 ounces at capture (foiu-tli column). In the same row, it is sliown furtlier that the expected weiglit for a 7.2-inch fish was computed to be 1.6 ovuices (fifth column) and that the expected lengtli for a 1.2-ounce lake trout would be 6.6 inches (third column). Agreement between most empirical and calcu- lated weights and lengths can be termed good. Discrepancies usually are small (full agreement at 14 lengths). The larger disagreements occur at 2' This numbor included all the lake trout weighed in the round, l.US presumably marked and 79 for which the ages from scale readings and deformed fins did not agree. 200 100 90 80 70 60 ^50 LU 40 O 2 30 O X 20 1.5 10 9 8 7 6 AGE DETERMINATION FROM SCALES OF LAKE TROUT ■I I , , , , |,,,.|i...|....|....|i. M |....|.i..|..ii | iiii|i.ii|.i.i|...i, . .T U ^ ' I ' I 37 ' 1 ' ' " I ■' "r log W = -2.470 + 3.112 log L or W= 3.390xI0'l"" 1 I I , I I I I I ,1 ,i,iImi, iiiil ,iil , 1„ In liJ 2 3 456789 10 20 LENGTH (INCHES) 30 40 FioiRE 18. — Length-weight rehitiou of 1,197 lake trout from northern Lake Michigan. (Dots give empirical values line represents values obtained from solution of the length- weight equation]. 38 Table 1/ FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE -Relation between total length (inches) and weight (ounces) of lake trout from northern Lake Michigan, also lengths and toeights calculated with the length-weight equation [Based principally on lake trout recaptured from the 1944-46 plantings of marked fish. See text for details] Num- Total length Weight Num- Total length Weight Num- Total length Weight ber ber of ber of of fish Actual Calculated Actual Calculated fish Actual Calculated Actual Calculated fish Actual Calculated Actual Calculated 1 7.2 6.6 1.2 1.6 24 13.0 13.0 9.0 9.9 10 17.2 17.5 25.2 23 8 1 8.0 7.6 1.9 2.2 15 13. 1 13.1 10. 1 10.2 8.- 17.3 17.5 25.1 24.2 1 8 3 «.3 2.5 2.5 19 13.2 13.1 10, 1 10.4 3 17.4 17. I 23.4 24.6 2 8.4 8.4 2.6 2.6 20 13.3 13.4 10,9 10.7 6 17.5 17. S 26.6 25. 1 2 8.6 8.6 2.7 2.8 32 13.4 13,4 10,8 10.9 6-. 17-6 17,3 24.0 26,6 2 8.7 8.6 2.8 2.8 25 13.5 13,5 11,2 11.2 10 17.7 17 8 26,3 26,0 1 8.8 8.9 3.1 3.0 19 13.6 13.2 10 5 11.4 3. 17.8 17,9 26,8 26,4 1 8.9 8.8 2.9 .11 23 .-.- 13.7 13,7 11,6 11.7 3 - 17.9 18,4 29,4 26.9 1 9.2 9.5 3 8 3 4 30 - 13.8 13.8 12 12.0 13 18.0 18,0 27,6 27.4 2 9.3 9.3 3.5 3.5 12 13.9 13,8 12.0 12.2 2 18. 1 18,2 28,2 27.8 2 9.5 11.7 7.2 3,7 27- 14.0 14,0 12.5 12,5 2 18.2 18,2 28,2 28.3 3. 9.7 9.5 3 7 4,0 22 14. 1 14.0 12.5 12,8 4 18.3 18,4 29.4 28,8 4 9.9 9.5 3.8 4,3 30 14.2 14.2 13.0 13, 1 1 18.4 18.4 29.6 29,3 4 10.0 11. 1 6.0 4,4 26 14.3 14.4 13.6 13,4 4 18.5 17.8 26.6 29,8 3 10. 1 10.3 4.8 4,5 27 14.4 14.4 13.7 13,7 5 18 6 19.1 32.7 30.3 4 -- 10.3 10.7 5.4 4.8 22 14.5 14.6 14. 1 14,0 4 18.7 18.8 31.2 30 8 1.- 10.4 10.4 4.9 5.0 24 ...- 14.6 14.6 14,3 14,3 5 18.8 18.8 31.5 31 3 3 10.6 10.6 5.3 5. 1 24 14.7 14,6 14.4 14.6 1 18.9 19.8 36.8 31.9 4 10.6 10.8 6.6 5.3 17 14.8 14,8 14.8 14.9 5 19.0 19.3 33.9 32,4 6 10.7 10.9 5.7 6.4 14 14.9 14.9 15.1 15-2 1 19.1 21,5 47,8 32,9 5 10 8 10.7 5.5 5.6 14 16.0 15.1 15.9 16.6 2 19.2 20,0 38,2 33,6 2 10.9 10.7 5.4 5.7 17 15.1 16.2 16. 1 15.8 4 19.3 19,7 36,2 34,0 10 11.0 11.5 6.7 5.9 17 15.2 15.2 16.3 16.2 2 19.4 19.0 32,4 34,6 8 11. 1 11.2 6 3 6.1 17 16.3 16 3 16.4 16.5 1 19 5 18.9 32.0 36, 1 9 11.2 11.5 6.8 6.2 18 16.4 16.4 16.7 16.8 1 19.6 19.3 34.0 36 7 9 11.3 11,4 6.6 6.4 23 15.5 15.6 17.6 17.2 1 19.7 20,7 42.5 36,2 11 4 11 3 6.6 6.6 23 16.6 15.6 17.5 17.5 1 19.8 19,6 35. 6 36,8 7 11.5 11.3 6.5 6.8 12 16 7 1.5.7 17,9 17.9 12 .--. 20.0 20, 1 38.8 38,0 9 11.6 11.7 7.1 7.0 13 16 8 16.1 19,4 18,2 1 20,1 19,7 36.2 38,6 12 11 7 11 8 7.3 7.2 16 15.9 16.0 18.9 18,6 1 ---- 20,2 19,7 36,5 39,2 8 11.8 11. S 7.4 7.4 7 16.0 15, 6 17.7 19,0 I 20.3 20,6 41,0 39,8 17 11.9 11.9 7.5 7.6 10 16.1 16 2 19.7 19,3 1 20,5 19,7 36,0 41,0 10 12.0 12.3 8.4 7.8 7 16.2 16,2 19.6 19,7 2 21.0 20,5 40,9 44,2 16 12. 1 12.2 8.2 8.0 4 16.3 16,8 21,9 20,1 1 21.2 21,0 48,0 46,6 21 12.2 12.2 8.2 8.2 11 .,-.. 16.4 16,4 20.6 20,6 2 21.5 22.6 65,4 47.6 10 12.3 12.6 8.9 8.4 14 16.5 16,7 21,7 20,9 1-- 21.6 21,9 50,2 48.3 18 12.4 12.3 8-4 8 6 7 16.6 16.5 20,9 21,3 1 21.8 22,0 61,0 49.7 18 12.6 12.6 8.9 8.8 4 16.7 16.5 21,0 21.7 3 22.0 21,3 46.0 51. 1 22 12,6 12.5 8.7 9.0 12 16.8 17.0 23.1 22.1 1 22,3 21,6 47.6 63.3 22 12.7 12.8 9.4 9.2 8 16.9 16.8 22.1 22.5 1 31,0 34,5 208 148 6 27 12.8 12.7 9.3 9.5 11 17.0 16.8 21.9 22-9 24 12.9 12.9 9.6 9.7 6 17.1 17.1 23.2 23.3 lengths where averages are based on one or a few fish. Other factors that possibly could have con- tributed to the discrepancies include: annual and seasonal fluctuations in condition; sex and state of gonads (of the larger, mature fish); and gear selec- tion. " It may, accordingly be held valid to use the equation to describe the general length-weiglit relation and thus estimate weight when length only is known or length when weight only is available. The calculated weights (table 17) show that lake trout would be expected to attain the weight of 1 pound at 15.1-15.2 inches, 2 pounds at about 18.9 inches, and 3 pounds at 21.5-21.6 inches. The length corresponding to I/2 pounds, the minimum weight at which lake trout may be taken legally in the State of Michigan, was 17M inches. To test whether the equation representing the length-weight relationship of the lake trout in the sample was also representative of younger fish, " See Farran (1936) and Deasonand Hile (1947) for discussions of the efTects of gill-net selectivity on the estimation of the length-weight relation. calculations of weight were compared with the weights of the control groups reared in ponds at Marquette, Mich. (Shetter 1951). The lengths at which tlie comparisons were made are average lengths at capture of the fish in the control groups. Lengths overlapping those of the lake-reared fish up to 10.7inciies are also inclmled in the tabulation. Length (inches) Number of fish (control groups) Measured weight (ounces) of pond-reared control group Calculated weight (ounces) 2.9 2.007 2.000 946 732 860 2«6 837 289 699 469 262 0.11 .15 .26 1.2 1.3 1.9 1.5 1.9 4.3 4-9 5.3 0.09 13 4 1 .27 (,4 _ 1.1 (5 7 _. 1.3 7.2 1.6 7.3 1.6 76 1.9 97 4.0 10.1 - 4.5 10.7 5.4 AGE DETERMIXATIOX FROM SCALES OF LAKE TROUT 39 The (liffiTcnces hotwec^ii m(>asure(l and calcu- lated weights for each length given did not exceed 0.4 ounce. The average weight of the pond- reared group was only slightly lieavier, 0.08 ounce, than the average calculated weight for all length- intervals represented by the group. GROWTH IN LENGTH The data presented on growth in length of marked lake trout include both lengths at capture and calculated lengths (based on scale measure- ments) at the end of the several years of life and at time of foi-mation of the 0-mark in the first field of growth. All calculations of length were made by direct proportion, that is, on the assump- tion that the ratio of length of fish to diameter of scale is constant at all lengths attained by the fisli after completion of the 0-mark. Although the materials at hand are not suitable for a discrimi- nating test of this assumption (range in lengths is too short and lengths at the ends of the range are represented by inadequate numbers of individ- uals), such data as are available indicate that any systematic errors, from the use of direct propor- tion, must be extremely small. Lengths at Capture The measured lengths of the marked lake trout of each age group, at the time of capture, extended over a wide range which was somewhat greater for the older than for the younger fish (see figure 20). The range within a single age group (year classes combined) varied from 5.4 inches for age-group II to 12.6 inches for age-group III with intermediate ranges for the remaining age groups (table 18). Despite wich- ranges in lengths, the mean lengths for each year of age reached by the three year T.^BLE IS.— Mean length (inches) and ranges of length at time of capture, of the year classes of marked lake trout' by age group ' Item Age group II III IV V VI 1944 year class: .Mean length 13.4 9.9-20.0 16 12.9 9. 7-22. 3 190 12.2 9. 9-16. 4 49 12.8 9. 7-22. 3 255 15.2 12.8-21.0 10 14.2 10.5-21.0 555 14.5 11. 1-20.0 167 14.3 10. 5-21. 732 15.1 13. 4-19. 7 17 15.8 10. 0-22. 240 16.6 13.0-21.6 23 15.8 10.0-22.0 280 Range Number of fish 1945 year class: Mean length Range N'umberof fish...' 194(5 year class: Mean length Kange .Number offish ... Combined year classes: .Mean length. Range Number offish.... 10.0 7. 2-12. 6 31 9.9 8.0-12.0 8 10.0 7. 2-12. 6 39 15.6 12. 2-20. 2 13 I.V6 12. 2-20. 2 13 classes of marked lake tiout were remarkably close together. \o represtnitatives of age-group II of the 1944 year class were taken by the fishermen, but the mean lengths of the 2-year-olds of the 1945 and 1946 year classes differed by only 0.1 inch. Tile mean lengtlis for age-groups III, IV, and V in all three year classes had maximum differences of 1.2, 1.0, and 1.5 inches, respectively. Tlie year classes of marked lake trout planted in Lake Michigan not only grew at similar rates but, regardless of environmental difi"ercnces, they also grew at about the same rate as control groups reared in ponds at tiie State Fish Hatchery, Marquette, Mich. The pond-reared lake trout of the 1944 year class had grown 16.6 inches in lengtli by October 1948 (age-group IV). None of the 1944 year class of marked, lake-reared lake trout were captured in October 1948, but the average length of trout in age-group IV caught from April through September was 15.2 inches which, as would be expected, was somewhat below tlie average for the fish taken only in October. The pond-reared lake trout of the 1946 year class were 10.1 inches long when they were measured in October 1948 (age-group II). Although no re- coveries from the lake-reared fish of the 1946 year class were made in October 1948, the average length of 9.9 inches for fish in age-group II caught from May tlirough September is not far below that for the pond-reared lake trout of the same year class. The best comparison of lake- and pond-reared lake trout comes from the more plentiful samples of the 1945 year class which were measured in May 1948 when they were members of age-group III. At this time the pond- reared fish were 11.7 inches long and the marked, lake-reared fish averaged 11.9 inclies long (table 19). Table 19. — Comparison of total lengths {inches) of take- reared, marked lake trout with those of the pond-reared control groups (.Number of fish in parentheses] Year of planting ' 1944 1945 1946 Pond-reared trout: .Average length- 16.6(200) Oct. 1948 15.2(10) Apr.-Sept.,1948 11.7(378).. May 1948.. 11.9(20). . May 1948 10.1 (196) Oct. 1948 9.9 (8) May-Sept.. 1948 Time of measurement- - I,ake-reare of cajjture as the following tabulation demon- strates: The marked fish recaptured as members of age-groups II, III, and IV measured 10.0, 12.8, and 14.6 inches long. Calculated lengths for the same years of life were 8.7, 11.2, and 13.7 inches. Whereas the calculated lengths give the size of the fish at the beginning of the growing season, the fish were caught somewhat later in the year at various times during the growing season, hence, were expected to be longer. Lengths, obtained by adding increments of growth, for fish in their fifth and sixth years of life show that in those years the lake trout actually continued to grow at rates only slightly lower than those during the earlier years of life (excepting the firet year). The relation of the calculated lengths to tlie empirical data is shown in figure 20. The mean annual increments of growth gradually decreased as tlie lisli became older from 5.9 inches the first vear to 2.8 inches the second 42 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE MEAN LENGTH AND RANGE IN LENGTH OF MARKED LAKE TROUT AT TIME OF CAPTURE COMPARED WITH MEAN CALCULATED LENGTHS T — [ — 1 — I — I — I — r • MEAN LENGTH AT TIME OF CAPTURE X MEAN CALCULATED LENGTH Q l I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I SONDJFMAMJJASONDJFMAMJJASONDJFMAMJJASONDJFMAMJJASONDJFMAMJJAS FIRST YEAR SECOND YEAR THIRD YEAR FOURTH YEAR FIFTH YEAR SIXTH YEAR Figure 20. — Mean length and range in length of marked lake trout, at time of capture compared with mean calculated lengths obtained by adding annual increments of growth (assuming January 1 the date growth is completed). Vertical broken lines give range of lengths, and dots the mean lengths at capture. Calculated lengths are shown along the solid, diagonal line. year, 2.5 inches tlie third, fourth, and fifth jears, and 2.4 inches the sixth year. Factors of Discrepancies in Estimates of Growth Several factors were considered as possible causes of the discrepancies in the estimates of growth made from the different age groups of marked lake trout: (1) condition of the fish; (2) sex differential in growth; (3) selectivity of nets employed by the fishery; (4) selectivity of lamprey predation. The effects of the first two were not considered important. Nearly all fish captured were taken during the summer months, thus seasonal changes in condition were not a factor. Combining data on the three year classes masked the annual differences Sexual differences had not developed on these fish, most of which were still immature; none cauglit was in gravid condi- tion. The other two factors affecting estimates of growth are discussed later. Selectivity of gill nets is an important factor which would have a tendency to cause discrepancies in estimates of the growth rate. Some marked lake trout (43.4 percent) were caught in the 4/2- inch-mesh gill nets of the whitefish and lake trout fisheries and others (56.6 percent) were taken in the 2j2-inch-mesh gill nets of the chub fishery. The percentage of the total catch of lake trout taken by the 4)2-inch-mesh nets decreased from 91.3 in 1947 to 17.5 in 1950. At the same time the percentage caught in tlie 2}2-inch-mesh nets increased from 8.7 to 82.5. During this period lake trout were becoming so scarce that fishermen were AGE DETERMINATIOX FROM SCALES OF LAKE TROUT 43 turning more and more to cliul) fishing with tho small-mesh nets. A gill net made of a single size of mesh tends to catch the larger fish of the younger age groups but, as the fish grow larger in later years this relation between size of fish and size of mesh in the nets is reversed and the net then catches the smaller individuals of the older age groups. This reversal takes place when the fish are at an earlier age if small-mesh nets are used than if the fishing is done with larger-mesh nets. The marked lake trout of age-groups III and IV, caught in 2,'2-inch-mesh nets, were 1.3 and 0.2 inches longer than tlie mean calculated length for the age group, and those of age-groups V and VI were 0.4 and 4.2 inches shorter than the calculated lengtlis. Fish of all age groups, caught in the 4/2-inch-mesh nets were longer than those cauglit in the 2!2-inch-mesli nets and also longer than the mean calculated lengths for the age groups represented. The discrepancies for age groups II to V fluctuated between 1.7 and 1.2 inches without clear trend. For age-group VI, the difference (0.5 inch) was less than the other differences, but the reduction mav not indicate that the reversal to capture of the smaller fish of a year class was approaching for this net. Prob- ably, larger fish were no longer available for capture. Am- group Mean cal- culated length Length at capture offish caught in nets of: 2>4-inch- niesh 4H-lnch- mesh n 8.7 U.2 13.7 16.2 18.6 10.0 Ill 12.5 13.9 15.8 14.4 12.9 IV 14.9 V 17.5 VI . ... 19.1 Even though the large-mesli nets consistently caught the larger fish, the average size of lake trout taken in them and in the small-mesh nets increased as the fish became larger. Nets of each mesh size were static measures of a segment of a changing range of lengths within the population as the fish of each year class became older, hence, the mode of the lengths of lake trout caught in each net shifted from the lower toward the upper limits of its segment as the average size of the fish increased (table 21). T.\BLE 21. — Calculated lengths (in inches) of marked lake trout (year classes combined) caught in large- and small-mesh gill nets IDifferences are shown below the lengths of flsh caught in each pair of nets) .\ge group Mesh of net (inches) Number ' offish caught Average total length and range of length Lit cap- ture 2 (inches) Calculated lengths at end of year of life 1 2 3 4 5 6 / 4H \ r.i ( Mi I 2,4 / 44 \ 2'i 1 Mi \ 24 f 44 \ 24 39 187 64 272 449 64 215 3 10 10.0 (7.2-11.9). _ 3.5 5.4 8.5 12.9 (9.7-22.3) 3.8 3.8 0.0 3.9 3.7 .2 3.8 3.7 .1 3.2 2.6 .6 5.9 6.1 -.2 5 9 5.6 .3 0.0 5.5 .5 5.1 4.2 .9 9.2 9.0 .2 9.1 8.7 .4 S.8 8.2 .6 8.1 6.0 2.1 11.7 11.6 .1 11.8 11.0 .8 11.4 10.6 .8 10.8 8.0 2.8 12.5(10.7-15.5)... 14.9 (10.3-21.0) 13.9(10.5-19.1) 17.5(13.0-22.0). 15.8 (10.0-20.1) __. 19.1 (17.7-2n.2)_ .. 14.4(12.2-18.0) 14.3 13.4 .9 14.0 12.9 1.1 13.6 9.9 3.7 v.. VI..._ _. _ 16.7 15.4 1.3 16.0 11.8 4.2 "ii'Q 13.9 5.0 4H 3.8 3.8 3.7 3.7 2.1 5.9 1.9 5.6 3.2 9.1 3.0 8.6 2.6 11.7 2.3 10.9 2.5 14.2 2.4 13.3 2.7 16.9 2.5 15.8 2.9 Length from summation of increments 19.8 m 2.0 17.8 1 Size of mesh in net not recorded for 16 fish. * Fish caught :it clifTerent times during the growing season. Their total lengths :ire not comparable with llu- oalculatcd lengths. Calculated lengths of the marked lake trout emphasize the differences in length between fish caught in the 4}^- and 2j2-inch-mesh nets. The differences increase in size with each year of life (table 21, fig. 21). Undoubtedly, "the small (average length at capture, 10.0 inches), slender lake trout of age-group II captured in large-mesh nets were caught by their teeth or by other en- tanglement in the twine. The size of the mesh ill the net could scarcely have been the determining factor in their capture. In fact, the small repre- sentation from age-group II in the sample (that from age-group III was six times as large) in- dicates that the fish in this age group were too small to be caught systematically in commercial nets of anv mesh size used. Evidently, too, these 44 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 3 4 5 6 YEAR OF LIFE Figure 21. — Calculated lengths of marked lake trout (year classes combined) caught in large- and small-mesh gill nets For each age group the calculated lengths of the fish caught in 4!j-inch-mesh nets are connected by a solid line and those of fish caught in 2H-inch-mesh nets by a broken line. As all age groups represented in the sample are shown in the same graph, the curves do not have a common base, hence none is shown. Consult table 22 for values (inches of length) of points on the curves. The numbers of fish taken by each net are shown in parenthetical boxes. lake trout were the smaller individuals of age- group II. Their mean calculated lengths were all smaller than those for the same years of life of the fish in age-groups III, IV, or V caught in either type of net (with the exception of the calculated length for the second year of age-group V caught in the small-mesh nets which was just 0.3 inch shorter than the one for age-group II). Nets of both sizes of mesh took fish of approxi- mately the same size from age-group III (larger- mesh nets captured only slightly larger fish). The difference in the calculated lengths of fish caught by large- and small-mesh nets increased gradually, as the fish advanced in age, from 0.1 inch in the third year of life of age-group III to 0.9 inch in the fourth year of age-group IV, 1.3 inches in the fifth year of age-group V, and 5.0 inches in the sixth year of age-group VI. The large discrepancies in the older age groups between the calculated growth histories of fish caught in 2^^- /2- and 4j2-inch-mesh nets leave some uncertainty as to the true rate of growth. Pos- sibly the samples from small-mesh nets give better estimates of the growth rates for the younger age groups and the fish from large-mesh nets may provide better estimates for the older age groups. Because of the different selectivities shown by the gill nets of these two mesh sizes, the marked and unmarked lake trout caught in nets of each mesh size were studied separately. The growth rates of marked and unmarked lake trout of the same year classes (1944-46) caught by 4}2-inch-mesh nets in northern Lake Michigan were closely similar. However, with but one exception, sizes ecjual at formation of the first annulus, the calculated lengths of the unmarked fish were somewhat lower, ranging from 0.2 inch at formation of the 0-mark to 1.2 inches at the sixth annulus. The average annual increment of growth in length after the first year was 2.8 inches for the marked and 2.5 inches for the unmarked fish. The calculated lengths of the unmarked AGE DETERMINATION FROM SCALES OF LAKE TROUT 45 4 5 6 7 8 9 YEAR OF LIFE Figure 22. — Calculated lengths (sums of mean increments of growth in inches) of marked and unmarked lake trout of year classes 1944-46, and of the older year classes (1938-43) from the wild stock, caught by 4'2-inch-mesh nets in north- ernLake Michigan, areas 1-6. lake tiout (year classes 1944-46) caught by 2?^- iiich-mesh nets in northern Lake Michigan were also lower than those of marked lake trout caught in the same nets. In fact, the differences between their calculated lengths ranged from 0.4 inch at formation of the first annulus to 1.1 inches at the fifth annulus. The average difference was 0.2 inch greater than the average difference between the groups of marked and unmarked lake trout caught in large-mesh nets. The average annual increment of growth in length for the fish from small-mesh nets was 2.4 inches for both marked and unmarked lake trout but the marked fish were already 0.4 inch longer than tiie luumirked fish at formation of the first annulus (table 22, fig. 22). Although marked and unmarked lake trout of the same year classes caught by small-mesli nets were somewhat smaller than those caught in the large-mesh nets, the calculated lengths of the unmarked fish retained about the same relative position below those of the marked fish that the unmarked fish had to the marked fish caught in large-mesh nets. Table 22. — Calculated lettylhs (sums of mean increments of growth in inches) of marked and unmarked lake trout of year classes 1944-46 caught in Lake Michigan [Increments of growth in parentheses] Locality ot capture and group o( lake trout Mesh of nets (inches) Number offish Calculated lengths at year of life .\verage incre- 1 2 3 4 5 6 ment of growth .\reas 1-6: Marked 1 Hi 565 3.8 5.9 9. 1 (3.2) 8.7 (2,8) 0.4 8,6 (3 0) 11.7 (2.6) 11.3 14.2 (2. 5) I.t 6 16,9 (2.7) 16.2 (2.6) 0.7 15.8 (2,5) 14.7 (2.1) 1.1 13.2 (2.1) 1.5 19.8 (2,9) 18.6 (2.4) 1.2 17,8 (2.0) 17.0 (2.3) 0.8 14.8 (1,6) 2,2 Unmarked 1 4K 29 3.6 5.9 (2. 6) (2 .11 Diflerences in calculated lengths 0.2 3.7 0.0 5.6 0,4 10,9 <■> :il 0.6 13.3 (2.4) 12.6 (2.4) 0.7 11.1 (2 01 .\reas 1-6: Marked _ f 2H 738 / 2M 38 3.2 5.2 7. 8 10. 2 (2 6) '2 41 (2. 4) Differences in calculated lengths 0.5 2.5 0.4 4.6 0.8 6,9 (2.3) 0.9 0.7 9.1 (2,2) Area 8: 1 2H 76 (2. 6) Differences in calculated lengths of unmarked fish: Areas 1-6 and area S 2H 0.7 0.6 11 IS 46 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE The discrepancies miglit have been explained on the basis of annual fluctuations of growth, had not the calculated lengths from fish of all the age groups within each year class of unmarked lake trout varied consistently about a lower mean than those of the marked fish. Evidently, the larger size of marked lake trout over unmarked fish of the same year class is a real rather than apparent difference, which suggests that the marked fish may have derived a certain advantage from the hatchery environment during their first summer that carried over into later life. The lake trout of year classes 1944-46 from area 8, caught in small-mesh nets, were decidely smaller than the northern wild stock caught in these nets. The average calculated length of the southern fish at the first annidus was only 4.6 inches and the average annual increase in length to the sixth year of life was 2.0 inches (table 22; fig. 23) compared with a calculated length of 5.2 inches at the first annulus and an annual increase of 2.4 inches for the northern fish. A major difference between samples of marked lake trout from 2}^- and 4/2-inch-mesh nets was the near absence of Lee's phenomenon in the data for the fish taken by the latter gear (fig. 24). These fish were subject to little or no selectivity from the nets, for few of tlie marked lake trout grew large enough to exceed the catching potential of the large-mesh nets. Another factor in bringing about apparent decline, even cessation, of the growth of marked lake trout with increase in age is believed to be destruction by sea lampreys of the most rapidly growing fish. Lengths, at capture, of marked lake trout in age-group V were little greater than those of fish a year younger; and lengths of fish in age- group VI were actually smaller than those in age-group V. A high percentage of the larger specimens in age-groups V and VI (28 percent of those caught in 1951) bore scars or open wounds made by lampreys. Smaller fish were unscarred; hence it is thought that lamprey predation is most severe among larger lake trout 14 or more inches long. It is possible, nevertheless, that small lake trout which have been attacked by lampreys die immediately so they do not come into the nets with wounds as do the larger fish. Hall and Eliott (1954) found also an increase of scarring with increase in length of the fish for the white sucker (Catostoinus commersoni) . They showed that incidence of scarring was consistently greater among suckers more than 10 inches long than among smaller fish and near 100 percent for fish 19 to 20 inches long. Thus the larger fish of the younger age groups and nearly all in the older age groups were being eliminated leaving only small, slow growing individuals. Wild and hatchery lake trout of the same year classes were subject to the same selectivity by the nets and the same predation by lampreys. The marked lake trout and the wild stock of year classes 1944-46 were comparatively free from atta(!ks by lampreys until they were about 14 Figure 23. — (.'alculated lengths (sums of mean increments of growtli in inclies) of marked and unmarlsed lake trout (year classes 1944-46) caught in 2'i-inch-mesh nets. AGE DETERMINATION FROM SCALES OF LAKE TROUT 47 19 - 18 - 17 - * 16 - (^ 15 _ UJ I • 1 14 _ * X 13 — ■J) ii_ 12 ' 8 o A X " (- ta z 10 — lij —1 M ^ 9 ~ • < t- O 8 _ 1- '=' 7 UJ 1 _ t < 4 6 — A. (_J _/ % — 4 - 3 2 1 - 1 1 1 1 " I 2 3 4 5 6 YEAR OF LIFE FiGiRE 24. — Calcuhited lengths of age groups of marked lake trout caught in -iH-inch-mesh nets (year classes combined). Symbols: diamonds, age-grovip II; dumb-bells, age-grovip III; dots, age-group IV: triangles, age-group V; squares age-group VI. inclies long, during tlieir fourth year of life. Fish from earlier year classes were suhject to (lie selectivity of largc-mesh nets for a longer period of time than the marked fish, but to a lower level of lamprey infestation because they were caught before the lampreys had made apprecial)le inroads into the lake-trout population in their areas of tlie lake. The best estimates available of the growth of lake trout in the lake before sea lampreys enteied it in large numbers are from data provided by the wild stock from the earlier year classes. In the northern part of the lake, areas 4, .5, and (1, sixteen individuals of year classes 1939-48 were caught by large-mesh nets in 1947. These fish were considerably larger at each year of life than the surviving fish of year classes 1944-46 caught in the same nets from 1947 to 1951. The average calculated length of the lake trout in the earlier year classes at formation of the first annulus was ().9 inches and the average annual increase in lengtli to the sixth annulus was ,S.O inclies com- pared witli .5.9 inches at the first annulus and an annual gain of 2.8 incites for the marked fish of year classes 1944-46 (tables 22 and 2.3, fig. 22). The early year classes of lake trout tliat lived in southern I^ake Michigan were rei)resented by two groups, both captured in 1947 i)y large-mesh nets. The larger sample of 97 fish (82 of which were of year classes 1939-43) was taken in area 7 off Montague, Michigan (Van Oosten 19.")0). The otiier group contained 17 lake trout of tlie same year classes from the collections of fish witli deformed fins caught in area 8 off South Haven, Mich. The average calculated lengtlis of the Iwo groups differed little from the second to the 48 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE Table 23. — Calculated lengths {sums of mean increments of groivth in inches) of unmarked lake trout caught by 4V2-inch-mesh gill nets in 1947 in Lake Michigan [Year classes 1939-43 combined] Number offish Calculated lengths at years of age Average in- crement 01 Locality of capture • 2 3 4 5 6 7 8 9 growth to sixth annulus Areas 4-6-. --- f 16 4.0 6.9 10.0 (3.1) 8.7 (3.6) 9.0 (2.9) 8.8 (2.7) 12.8 (2.8) 12.1 (3.4) 12.1 (3.1) 12.1 (3.3) 16.1 (3.3) l.'i.S (3.2) 15.4 (3.3) 16.3 (3.2) 19.0 (2.9) 18.3 (3. 0) 18.7 (3.3) 18.4 (3.1) 21.8 (2.8) 20.9 (2.6) 21.2 (2. 6) 21.0 (2.6) 24.2 26.4 28.7 } 3.0 Area 7: ) Off Montague, Mich i 82 6.1 23.1 24.7 1 3. 1 Area 8: f Ofl South Haven, Mich l 17 3.6 6.1 23.6 23.2 26.3 '25.0 I 3.0 Areas 7 and 8 combined (from 3rd to 8th years){ 99 j 3.0 seventh aiimilus. Differences at the eighth annu- lus were due to tiie small number of measurements (6 for area 7 and only 1 for area 8). As explained earlier, the calculated length at the first annulus for lake trout caught in area 7 (as published), was not based on the same criteria as the data on the O-mark and the first annulus treated in this paper. For this reason, the calculated lengths of the fish from areas 7 and 8 were combined only from the second to the eighth annulus. The mean calculated length at the first annulus of the fish from area 8 was 6.1 inches and the average annual increase in length of the combined groups was 3.0 inches (table 23). Comparison cannot be made of these figures with like figures from lake trout of year classes 1944-46 from the southern areas of the lake as none of those fish were caught in large-mesh nets. The calculated lengths for the early year classes, however, were very much larger than those for the fish of year classes 1944-46 caught in small- mesh nets (table 22). Selective destruction of the more rapidly grow- ing individuals by sea lampreys and by nets of the commercial fishery leads to a decrease of gi'owth rate with increase of age which would not exist within a stock not subject to such selective mor- tality. It is a natural consequence of continued selective destruction of large fish, that each older age group should be composed of slower-growing fish than the younger age groups. Because the combined eft'ects of biased samplitig and selective destruction of the marked lake trout by lampreys cannot be measured, it must be recognized that tiie "normal" growtli of lake trout in Lake Michigan probably was not determined precisely. However, tlie use of summations of the mean increments of growth in length to describe general growth tends to lessen the effects of selective mortalitv and thus to vield curves more representative of the true rate of growth than otherwise could be obtained from these data. A third cause for discrepancies in estimates of growth of lake trout in Lake Michigan, not, however, affecting area estimates, is geographic differences in size and growth. Lake trout in- habiting the northern part of the lake were larger at each year of life than those in the southern part of the lake. Tliis difference in size is ap- parent in comparisons of fish in the same year classes caught in nets of the same mesh size. Examples: the early year classes (1939-43) caught in 4}^inch-mesh nets (table 23, fig. 25), and the later year classes (1944-46) caught in 2)^inch- mesh nets (table 22, fig. 23). For tliese and other groups of lake trout from the two parts of the lake, the differences appear to stem principally from a slower growth of the southern fish during their first summer to formation of the first annulus. The southern fish of the early year classes caught in the large-mesh nets, at formation of the first annulus, were 0.8 inch shorter than a similar group of the more northern fish, but the average annual increases in length in later years were identical. Those of the more recent year classes caught in 2K-inch-mesh nets, at formation of the first annulus were 0.6 inch shorter and the average annual increases in length were 0.4 inch less than the annual gains of the unmarked northern fish of the same year classes. The consistency of the discrepancies between the calculated lengths of lake trout from southern and northern Lake Michigan indicates that they represent a true geograpliical difl'erence of growth between the two populations. GROWTH IN WEIGHT Weights were available for only 1,118 of the 1,319 marked lake trout, but these were sufficient AGE DETERMINATION FROM SCALES OF LAKE TROUT 49 4 5 6 YEAR OF LIFE Figure 25. — Calculated lengths (sums of mean increments of growth in inches) of unmarked lake trout caught in Lake Michigan by 452-inch-mesh nets in 1947. Year classes 1939-43 of the fish from areas 4-6 were combined as were those from areas 7 and 8. for determination of mean weights at capture of the fisli in each age group represented. Further information on growth in weight was obtained by calcuhitiiig weights corresponding to calcuhited lengths at the end of the several years of life and and at tlie time the 0-mark was formed. These calculated weights were computed by the length- weight ecjuation. Weights at Capture The range of weight in all age groups of the marked lake trout was large, as would be expected from fish that differed so greatly in length. Both the average weights and the ranges of weight of the different age groups are presented in table 24. In 9 of the 12 age groups for which data are given in the body of the table, the weight of the heaviest fish was more than 5 times that of the lightest (the advantage was more than 10-fold in age- group IV of the 1945 year class). In the remain- ing 3 age groups the heaviest trout weighed 2.0 to 4.5 times as much as the liglitest. Despite the great variability in weight, the mean weights of certain age groups of tlH> different year classes were similar. The average weight ranged from 4.3 to 4.4 ounces in age-group II, from 6.6 to 9.7 ounces in age-group III, and from 11.2 lo 15.2 ounces in age-group IV. The range of the mean weights was somewhat larger in age-group V (15.2 to 27.4 ounces). Comparabl(> data on the weiglits of the fish in age-gi'oup VI were not available. Table 24. — Mean weight (ounces), at time of capture, of the year classes of marked lake trout, by age groups Item Age group II III IV V VI 1944 year class: 7.0 3.5-32.0 10 9.7 3. 9-22. 4 174 6.6 3. 7-21. 5 38 9.0 3.5-,12.0 222 15.2 9. 1-46. 9 11.2 4. 7-47. 8 523 14.0 6.0-41.0 116 11.8 4. 7-47. 8 648 15.2 10.5-21.2 11 20.5 5. 1-48. 8 184 27.4 8.2-50.2 12 20.6 5. l-.5fl. 2 207 1945 yeur class: Sle:in weight Range Xumber offish 1946 year cl;iss: .Mean weight Range Xumber offish Tomhined year class: Mean weight 4.4 1.2-8.3 28 4.3 1.9-8.5 8 4.4 1. 2-8. 5 3fi 26.9 11.5-36.5 5 26.9 11,5-36.5 Xumber offish 5 Calculated Weights The growth in weight of the marked lake trout (as determined by the length-weight equation from the calculated lengths shown in table 20) was slower in the earlier than in the later years of life. Wiiereas the most rapid growtli in lengtli occurred during the first year, growtli in weight proceeded slowly through the second year. Tiie weights calculated for the first year of life were typically less than 1 ounce and averaged only 3.0 ounces at the end of tlie second vear. The annual 50 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE Table 25. — Weights of the marked lake troui at capture and as ralriilated for the end of each year of life ' [Weight in ounces] Year planted Number o specimens Weight at capture Calculated weight at end of year of life Age group measured weighed 1 2 3 4 5 6 31 8 28 8 4.4 4 3 4.4 7.0 9.7 6.6 9.0 15.2 11.2 14.0 11. S 15.2 20.5 27.4 20.6 26.9 0.15 .18 .17 .18 .23 .20 .22 .18 .22 .20 .20 .17 .20 .15 .20 .07 0.57 1.10 .66 1.16 .85 .85 .90 .85 .94 .85 .90 .76 .72 .76 .72 .34 2.6 3.0 2.6 3.6 3.4 3.0 3.4 3.2 3.0 2.8 2.8 2.2 2.6 2.3 2.5 1.2 jj . 1946 16 190 49 10 174 38 8.2 7.4 5.7 7.2 7.6 6.6 6.1 6.4 5.0 5.6 4.7 5.4 2.8 1945 III 1944 10 555 167 9 523 116 13.7 11.7 12.5 12,0 9.2 10,4 10.4 10,2 5.4 IV 1944 17 240 23 U 184 12 14.9 17.9 19.0 17.5 9.5 V --- VI .. 1945 13 5 16.2 Number of specimens. Mean increment of gro\ Weight from summatio Mean calculated weigh Increments of mean we 1,319 0.21 .21 .21 .21 1,319 0.65 .86 .86 .65 1.319 2 1 3.0 2.9 2.0 1,280 3.4 6.4 6.4 3.5 1,025 5.2 11.6 11.3 4.9 293 7.3 18.9 17 4 6.1 13 6.7 25.6 16,2 ght -1.2 I Weights calculated with length-weight formula from calculated lengths shown in table 20. 3, ' ^ I UJ 5 I 14 2 3 YEARS OF AGE Figure 26. — Calculated growth in length and weight of marked lake trout [summation of ann\ial increments of growth]. addition of weight increased sharply from 2.1 ounces in the second year to 3.4, 5.2, 7.3, and 6.7 ounces in succeeding years. The calculated incre- ments of weight of fish in the older age groups (especially age-group VI) would have been larger except for selective mortality of the more rapidly growing lake trout which resulted in reduction of the average length increment (table 25, and fig. 26). Calculated weights obtained by summation of the mean increments of growth in weight were slightly smaller than weights of the fish at capture for tlie same reason that the calculated lengths were smaller than the measured lengtlis. The differences in weight ranged between 0.2 and 2.6 ounces as shown in the following tabulation: Year of life 2 3 4 5 6 Weight from summa- tion of calculated increments 3.0 6.4 11.6 18.9 25.6 Age group II III IV V VI Weight at capture 4.4 9.0 11.8 20.6 26.9 PROGRESS OF SEASON'S GROWTH As a first approach to the estimation of the progress of the growth of lake trout during the growing season, tabulations were prepared of the sizes attained by the age groups of the marked fish at capture in each month of the year. AGE DETERMINATION FROM SCALES OF LAKE TROUT 51 I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I MJ JASONDJFMAMJJ ASONDJ FMAMJ JASONDJ FMAMJJASO n m EZ ¥ AGE GROUP Fir.iRE 27. -Mean length? and mean weights of tlie marked lake trout at time of capture. Year classes 1944-4fi com- bined. [Curves drawn by inspection.) The average lengths of lake trout of the 1944-46 year classes of the same age group were originally tahulated by semimonthly periods, but as division of the data into shorter time intervals did not provide additional information, the averages of table 26 (see also fig. 27) were based on monthly groupings. Altliough the month-to-month changes in the average lengths of the age groups were de- cidedly irregular, the figures do give the general impression that much of the increase in length took place in the late summer and fall. In other words, rapid growth seems to have started about the end of June and to have continued at least through October, possibly longer. The records of average weight of the age groups at capture support a similar interpretation (table 27, fig. 27). T.\Bi.E 26. — Average lengths (inches) of marked lake trout at time of capture (Data for 1944, 1945, and 1940 year classes combined.' Number of specimens in parentheses] .lanuary February March April May June.- , July .\ugust .. September- October November. December-. Mean length.. Age group 8.0 (1) 8.5 (3) 9.8 C4) 9.7 (5) 9.8 (12) 9.9 (7) III 11.5 (7) 10.0 (39) 15.4 (1) 9.9 (1) 12.0 (2) 11.6 (8) 11.8 (22) 11.9 (36) 12.7 (30) 12.9 (64) 13.5 (72) 11.9 (7) 12.4 (8) 14.1 (4) IV 13.8 (27) 14.6 (13) 14.1 (17) 14.9 (80) 13.9 (156) 13.9 (120) 14.0 (183) 14.8 (109) 1.^3 (13) 15.9 (6) 15.6 (4) 15.0 (4) 12.8 (255) 14.3 (732) 15.0 (24) 15.2 (6) 16.3 (5) 15.7 (24) 15.8 (81) 15.8 (6(1) 16.7 (34) 17.6 (33) 16.0 (12) 13.1 (1) 15.8 (280) I Lengths of the 13 fish in age-group VI omitted because the data arc too scattered to be of value in this table. 52 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE Table 27. — Average weight (ounces) of marked lake trout at time of capture (Data for 1944, 1945, anil 1946 year clas,ses combined in parentheses] ' Number of specimens Age group II III IV V 6.9 (1) 3.7 (1) 8.4 (2) 7.7 (1) 7.4 (20) 8.2 (28) 9.9 (26) 9.6 (57) 11.3 (69) 9.6 (5) 11.9 (9) 12.6 (4) 11.0 (19) 15.2 (13) 13.1 (16) 15.0 (66) 12.7 (1.65) 13.0 (80) 12.9 (172) 16.5 (102) 14.8 (12) 19.4 (6) 14.7 (4) 19.6 (4) 18.1 (18) 17.1 (4) March 17.6 (4) April 18.9 (19) May i.9 (i) 2.6 (3) 4.5 (4) 4.1 (3) 4.3 (12) 4. 2 (6) 19.7 (65) June July \ugust 22.8 (38) 23.6 (28) 30.2 (24) September 25.0 (7) 6,8 (7) Mean weight . _ - 4.6 (36) 9.9 (222) 13.6 (648) 21.9 (207) I Weights of the 13 fish in age-group VI omitted because only 5 fish were weighed and the data are too scattered to he of value in this table. More dependable data on the progress of the season's growth may be obtained by romputation of growtli from scale measurements. Examples of the distribution of these increments are contained in the records for the 555 lake trout of age-group IV from the 1945 3'ear class, the largest year class in the collections. Their increments of growth in length were computed by semimonthly periods (table 28). The amount of growth attained by individual lake trout in any stated time varied widely. By the end of April, the range in the amount of seasonal increment of growth in length was from nil to 1.4 inches. This range continued nearly constant and the mean advanced only slightly (0.14 to 0.40 inch) until the middle of July." In the latter part of July the range in lengtlis of the increments began to broaden and by the end of August the spread was 2.8 inches. In the fore part of August, some lake trout were still just beginning to grow whereas others had been grow- ing since the middle of March or possibly even longer. It was largely because of this wide spread in the time of the onset of growth that the average increment was still only 0.22 inch in the first half of June. Subsequent more rapid in- crease carried the average to 1.7 inches in the first half of September. Returns of lake trout were so sparse during the remainder of the year that dependable estimates of growth cannot be » iMp,v growth cannot be recognized on the scales until the first circulus haS been formed, a circumstance which probably accounts for the small propor- tion, at any time, of fish having as little as 0.2 inch caclulated growth. The smallest calculated length increment is more often 0.4 inch. Hence the fish usually had grown nearly \i inch by the time the annulus could be read with confidence. made from them. It is especially difficult to form a judgment as to the time the season's growth ends. It appears from the data in table 29 that the growth of the fish in age-group IV had not been completed by the end of December, when the average increment (4 fish) was 1.95 inches or 0.64 inch below the figure of 2.59 inches computed for the full season from age-group V of the same year class. (The fish in age-group V that had not yet completed the fifth annulus gave nearly the same estimate of growtli in the fourth year, 2.60 inches, as did those on whose scales the fifth annulus was visible, 2.58 inches.) Records of tlie percentage of the season's growth completed by age groups of the 1945 year class up to various dates of capture, despite gaps in the data and the siaall numbers of fish on which certain percentages were based, give evidence of annual differences in tlie progress of growth and of irregular growtli in some years (table 29). These points are well illustrated by the curves in figure 28 which were fitted by inspection to the empirical data. The data were scanty for the lake trout of the 1945 year class in age-group II. The single trout captured in the first half of June had made no growtli. Percentages of growth completed by fish caught later in the season rose quickly to 51 in early August but fluctuated erratically thereafter. Seven fish recovered in December had grown more (percentage, 115) than the "expected" increment for the full season calculated from measurements of the fish in age-group 111. The 4 lake trout of age-group 111 caught in late April and early May 1948 exhibited no new growth, but those captured during the last half of May had completed 7 percent of the expected growth for the season. The percentage dropped ill early June, but thereafter it increased steadily (except in the first half of September) to 94 per- cent in early October. The single trout caught in December had gained only 79 percent of the expected total increase. Age-group IV, captured in 1949, seems to have started growing early in the season. Possibly the single lake trout with new growth in January could be dismissed as aberrant, but all semimonthly collections from the latter half of March onward contained some fish that had begun to grow. The advantage of this early start was later lost, how- ever, for the percentage of new growth remained AGE DETERMINATION FROM SCALES OF LAKE TROUT 53 ■PS p a n li is £| o ■^re^/;x^l^|:-^^c §3! 1 I I I l.-HNr-accoiCtr^t^r-ociiJC*':— " \ ;— E S 1 :^-H ;« : ; .^ ^g « :::;:;::;:; 1 J2 B O 1 -" i'""^ i ; ; ; "S 1 ! ! : i I ; i i ; i"' ; i i x: o O 1 : i : : ; : i i'" ; : i^ ; 1 ';;::;; ^ '> CO '•'<'•'• 'i 'fe B a m ; i'^ i : i : : i i i 1 ; ! M! i i|-- : ; i : i T"^-^^ i i i M i : i ; ^^ s ■< 1 1 i^N^^ eo«'^N I i • ; i" ; ; : i i i i ; ss iC _< itCO-*^ t*40 Tj-r-.-. i 1 . ;;;;;;!;!:; 1 (O> ;;;;;;;;;;; S2 1 I ; 1 1 ! I 1 j ! j d 1 g i- i 1 I • d lO N ' NO d >. C 03 •-9 1 »o .—1 . . d 1 "* I 1 I ' d at _^ o c E £ O c O N -* *D 00 C o o d o" o - 00 d N ■* «D CO q e* W « ao "5 ; 1 : E ; > "CO J5S 1-^ ^E & . § X o (U F ox: s TJ a F > a a R c Sr * o £ •o a S i" J= = » F te a V) £ 3-S e S L i" - u. 54 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE Table 29. — Average percentage of season's growth completed at various dates during the season hy age groups of the marked lake trout from the 1945 year class [The bases for the percentages are the increments of growth for full seasons computed from measurements of the scales of fish of the next higher ape groups of the same year class] Age-group II Age-group III Age-group IV Age-group V Unweighted Date Number offish Average percentage Number of fish Average percentage Number offish Average percentage Number offish Average percentage average ' percentage 4 6 2 9 0.0 2.3 .0 .0 11 11 3 0.0 .0 .0 (1.0 16-31 - -- 1,2 Feb 1 15 .0 16-28 Mar 1-15 -- 16-31 16 21 40 79 31 36 47 100 57 71 17 4 1 4 2 1 3 2.3 1.2 5.4 5.0 5.0 8.5 13.5 15.4 29.0 40.6 53 7 66.8 63.7 60.6 80.7 83.4 62.6 Apr 1-15 1 18 48 22 32 27 14 11 24 5 8 4 .0 9.4 8.5 13.4 fi.7 8.0 30.8 54.9 65.2 88.9 70.5 92.4 .6 16-30 i 3 17 14 14 9 12 21 25 42 29 2 0.0 .0 7,2 3 8 19. 1 25.0 43.2 53.4 65.7 64.8 72.9 94.1 4.9 May 1-15 -- 4,5 16-31 8.5 June 1-15 --- 1 1 2 0.0 13.3 17.2 4,8 16-30 ... ._ 13,5 July 1-15 - 22.1 16-31 42.4 Aug 1-15 4 1 1 7 7 50.8 41.8 16.4 50.4 54.7 52.5 16-31 62.5 Sept. 1-15 54.6 16-30 69.8 Oct 1-15 69.8 16-31 Nov 1 15 16-30 Dec 1 15 7 114.9 i 79.3 4 75.3 1 58.6 81.9 2.56 2 36 2.59 2 24 31 190 555 240 ' In order that age-group IV. which was represented in nearly all semimonthly periods, would not exert undue influence on the trend oidy those periods which were represented hy one or more other age groups are included. 2 Based on the 13 fish in age-group VI. at 5 from mid-May through June. Beginning with the first lialf of July, the percentages were consistently smaller than those for age-group V and, with one e.xception (early September), were also below the percentages for age-group III. The erratic variation of the percentage of com- pleted growth for age-group IV during September- December can be attributed partially to the small numbers of fish in the samples, but the generally low level (61 to 83 percent; 75 percent for 4 lake trout caught in late December) is further evidence tliat the seasonal growtli was not completed at the end of the calendar year. As the average increment of growth of the 4 lake trout caught the last part of December was only 2.0 inches, the actual amount of growtli between December 31 (ages change on January 1) and the completed growth of 2.6 inches at formation of the fifth annulus was 0.6 inch. It was pointed out earlier that the average estimate of the growth of age- group IV for the entire season, calculated from measurements of the scales of lake trout in age- group V taken in 1950, was the same for fish without the fifth annulus as it was for those that had that annulus visible. However, the average increment for 11 lake trout caught the first half of January, which did not have new gi-owth on their scales, was only 2.3 inches (88.5 percent of the total increment), whereas the average incre- ment for an ecjual number of lake trout caught the last part of the month was 2.59 inches (100 percent of total increment). Increments for 4 fish taken between the first of February and the 15th of April were low (2.13 inches), but the average increment for 12 fish taken the first half of May (2.63 inches) showed a slight rise over that for January. These few fish, caught January to May, do not furnish definitely reliable information on the end of tlie growing season, however they do indicate that in certain years lake trout may continue to grow tlirough the winter months. The 25 lake trout of age group V taken in Jan- uary and February and a single fish caught in early April had not started to grow. The incre- ment of new growth on the scales of lak-e trout captured in the last half of April amounted to 9 percent of the expected total increment, but this percentage showed no clear tendency to increase during May and June. A sharp upturn, beginning in July, however, carried the percentage to 92 in late September (with a single exception to the trend in the first half of the month). The single AGE DETERMIXATIOX FROM SCALES OF LAKE TROUT 00 100 - 90 80 5 O 70 a. 60 50 40 30 20 I -o--o-^ JAN FEB MAR APR MAY JUNE V -^ /^ >-^- A _, _^..-'" jC^ in ^^ 12 o ■'■^ / / /> ° /■ / / /x / /x / ^ / / < / • / y A / / • / X / ^ X / k A 4 .'' / / ,-" / X / X / o/' O // A > trout of ajio-tiroup V caught in Doccmhor, however, liati compUUed only 58 percent of the cxi)ecte(l total growth. A start of growth followed by a stoppage or near-stoppage as demonstrated for age-group I\' in the last half of April through May, and for age-groii]) V in May and June, might he exiiecled to produce irregularities in the scale structure. Nevertheless, examination of the scales of lake trout of age-groups IV and V captured late in the growing season revealed no checks or marks that could be attributed to this stoppage. Some of the irregtdarities in the data of table 20 can be attributed to the inadequacy of the samples, but the majority give evidence that the coin-se of the season's growth v'aries considerably from one calendar year to another. (There is no evidence of a ju'ogressive change witli age), '{"his year-to- year \!iri(itioii iind the uncerlaiiit v as lo the tinu' growth ends (data were conflicting even among the best represented age groups) prohibit a general description of seasonal growth of the marked lake trout. Growth may start as early as March or as late as June. Once started, growth may follow a regular course; but in sonu' years it may stop, completely or nearly so, for a period of several weeks. The end of the season as well as the start probably varies from year to year. In some seasons growth may continue into the next cal- endar year. Because of the variation in the start and finish of the growing season, growth of lake trout in Lake Michigan is likely to occiu- in at least 9 or 10 months of the year, i)ossibly in even more. The most rapid growth, nevertheless, ap- l)ears normally to take place in Jtdy and August. The percentages at the right of table 29 indicate that nearly half of the total season's growth occurs in these months. The same set of figtn-es shows 56 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE that, in general, the lake trout gained about 30 percent of their growth sometime after the middle of September. The growing season for lake trout in Canadian waters is shorter. Kennedy (1954) found that the lake trout in Great Slave Lake "grow only between late May and the middle of September, with no growth at any other time." Of the seasonal growth of the lake trout in South Bay, Lake Huron, Fry (1953) stated, "The lake trout . . . add about 1 inch to their total growth increment for the year by mid-September. The total for the major year class represented in 1949 (the 1944 year class) . . . was estimated at 1.8 inches. This increment would indicate the rapid growth observed from June to September probably continued at least until mid-October." SUMMARY From 1 to 1)2 million liatchery -reared lake trout (average length 3.2 inches) were liberated into northeastern Lake Michigan in September of each of the years 1944-46. About 10 percent of these fingerlings were marked by the removal of fins. In the years subsequent to the plantings, 1947-52, fishermen captured 1,747 lake trout with abnormal fins of whicli only 1,507 were adequately documented. Of the latter group, 102 caught off South Haven, Mich., difTered so much from those caught in the northern part of the lake that all, or nearly all, were considered to be unmarked wild lake trout with abnormal fins; hence, they were excluded from the main sample. The scales of the remaining 1,405 fisli were studied to determine the validity of age readings from scales and the rate of growth of lake trout in Lake Michigan. Lake trout scales are small and have concentric circuli. They develop first as platelets adjacent to the anterior end of the lateral line when the fish are about 2 inches long and rapidly cover all the body except the head. Probably joung lake trout in Lake Michigan are fully scaled before the end of their first summer. Even though the scales were rather difficult to interpret, simple criteria for recognition of the annulus were determined. The annulus is gcn- erallj' indicated by wider spacing between circuli outside closely spaced circuli, but this arrange- ment, usually most clearly seen in the lateral fields, is seldom definite enough to be followed entirely around the scale. Other indications of an annulus are: a V-shaped pattern in the circuli of the lateral fields, a ridge across the posterior field, also such irregularities as broken or crooked circuli and fine accessory lines. An annidus is usually located by a combination of these criteria. The annulus was formed on the scales of some lake trout as early as the middle of March, of the majority during June and July, and of a few as late as the middle of August. In addition to the expected number of annuli for the marked fisli, a central check was found within the first annulus which has been designated the "0-mark." The scales of the unmarked, wild-stock lake trout from Lake Miciiigan exam- ined during this study also carried the central check (0-mark). Two readings were made of the markings on the scales. The ages read agreed on 96.8 percent of the specimens. The number of annuli read from the scales agreed with the age of the fish indicated by the deformed fin for 93.9 percent of the lake trout in the sample of presumably marked fish. Most of the disagreements were of 1 year but some were of 2 or more years. The principal difficulty in the way of determin- ing the accuracy of age readings from the scales of the lake trout from northern Lake Michigan resulted from the presence in the collections of a small percentage of unmarked fish. The exact number of these fish could not be comited but evidence from several lines of investigation led to the conclusion that nearly all the 86 fish, for which the age read from the scales disagreed with that indicated by the deformed fin, were unmarked lake trout. The average lengths of the age groups indicated by the deformed fins of the 86 "uimiarked" fish were very different from those of the age groups of the 1,319 "marked" fish (those with agreement between age indicated by the fin and that read from the scales); furthermore, the average length of the 86 fish decreased with increase of age. On the other hand, at ages read from the scales, the growth curve for these 86 fish was similar to that of the 1,319 "l)ona fide" recoveries. It was concluded, therefore, that the age read from the scales rather than tlu' age indicated by the deformed fin was correct for most fish. Tlu» evidence strongly indicates a liigli depend- AGE DETERMINATION FROM SCALES OF LAKE TROUT 57 ability of ago readings from lake trout scales. The reader does, nevertheless, need considerable experience with scales from fish of known age to become proficient in recognition of the 0-mark and annuli. The estimate obtained of the relation between weight in ounces and total length of the fish is expressed by the formula: log Tr= -2.4698+3.1 125 log L The range of total lengths at capture of fish within an age group of marked lake trout was wide. The average length for an age group of one year class, however, was close to those for the same age group of the other two year classes. Lake- and pond-reared fish had attained about the same lengths at 2, 3, and 4 years of age. The calculated lengths of the fish at various ages prior to capture were computed by direct proportion from the diameters of the annuli. The calculations from 2 scales were averaged. The calculated lengths (sums of the mean increments of growth in length) being lengths of the fish at the end of growing seasons were, as would be expected, somewhat smaller than the mean lengths of the fish of the same age groups at time of capture which was, in most cases, after the beginning of a new growing season. The lengths calculated from the fish in age- groups III-VI exhibited Lee's phenomenon of gradually decreasing values with increasing age. Most of the discrepancies are explained by selec- tive destruction of the most rapidly growing fish by nets and sea lampreys. Scars and open wounds made Vjy lampreys were found more often on large than on small lake trout. The destruction of the large, fast-growing fish could account for the small size of the fish remain- ing in the older age groups which were caught after the population had been materially reduced. Gill nets of the two sizes of mesh most com- moidy used in Lake Michigan caught lake trout of greatly different sizes. During tlie years marked lake trout were caught, the fishermen gradually shifted from use of large- to small-mesh nets. The large-mesh nets caught larger fish than the small- mesh nets and the difference became greater as the fish grew older. It is questionable, therefore, whether a general average gives a true estimate of the growth of these lake trout. The fish caught in the small-mesh nets may give the better esti- mate of the growth of the younger age groups, whereas those caught in the large-mesh nets may be more representative of the older age groups. Lee's phenomenon, prominent iti measurements of the first group, is almost lacking from the meas- urements of the fish in the latter group. Summing the increments of growth in length minimizes the efl'ects of biased sampling and selec- tive destruction of the fish. The weights of the marked lake trout were similar to the lengths in that the weights of in- dividual fish at capture varied greatly within age groups and the mean weights for the age groups at capture were slightly larger than the calculated weights. Although the most rapid gain in length occurred during the first year of life, the gain in weight was least in this year and much greater in later years. Seasonal growth of the marked lake trout re- flected the long period of annulus formation. The growing season was extended and variable. Growth for the three year classes indicated a long period of slow growth in the spring, rapid growth from the end of June through October, and slower growth again on into December. Monthly distribution of the increments of growth in length of the 1945 year class suggested that lake trout may occasionally have a somewhat longer season of growth. The average percentage of growth completed at semimonthly intervals for the sepa- rate age groups showed that the growing season varied consideraVjly from one year to the next. Not only the time of the beginning but also of the end of the growing season may vary several weeks, even months. Because of this lack of uniformity in the time of start and finish, growth of lake trout in Lake Michigan may be expected to take place in 9 or 10 months of the year. As large- and small-mesh nets caught fish of different sizes and the destructiveness of the sea lampreys increased during the years the marked lake trout were in the lake, it was necessary for estimation of the growth in length, to select fish of the same year classes caught in the same calen- dar years by nets with mesh of the same size. The marked fish (year classes 1944-46) caught in large-mesh nets were slightly larger than the un- marked fish also caught in the northern part of the lake, which suggests that the marked lake trout gained some small advantage from early care in the hatchery. Lake trout caught in large-mesh 58 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE nets in northern and southern areas of the lake could not be compared because no fish of year classes 1944-46 were caught in large-mesh nets. Those caught in small-mesh nets were consider- ably smaller than both marked and unmarked lake trout caught in these nets in northern waters. Lake trout that had lived in Lake Michigan before the sea lampreys became numerous were larger and had grown at a faster rate than the marked fish. Two samples of lake trout of these early year classes from the southern part of the lake, caught in 1947 by large-mesh nets were so similar they are believed to have been drawn from the same population, but one that differed from the northern population by an important char- acteristic. Growth during the first summer to formation of the 0-mark was much less than for fish in the more northern waters. Subsequent annual growth in length was the same in both areas. LITERATURE CITED Applegate, Vernon C. 1951. The sea lamprey in the Great Lakes. Scien- tific Monthly, vol. 72, pp. 275-281. Applegate, Vernon C, Bernard R. Smith, and Willis L. Neilsen. 1952. Use of electricity in the control of sea lam- preys: Electromechanical weirs and traps and electrical barriers. U. S. Fish and Wildlife Service, Spec. Sci. Rept.: Fish. No. 92, 52 pp. Applegate, Vernon C, and James W. Moffett. 1955. The Sea Lamprey. Sci. Amer., vol. 192, No. 4, pp. 36-41. Bahtlett, M. S. 1949. Fitting a straight line when both variables are subject to error. Biometrics, vol. 5, pp. 207-212. Brown, C. L D., and Jack E. Bailey. 1952. Time and pattern of scale formation in Yel- lowstone cutthroat trout Salmo clarkii Lewisii. Trans. Amer. Micro. Soc, vol. 71, No. 2, April, pp. 120-124. Butler, Robert L., and Lloyd L. Smith, Jr. 1953. A method for cellulose acetate impressions of fish scales with a measurement of its relia- bility. Prog. Fish-Culture, vol. 15, pp. 175- 178. Cole, Leon J. 1905. The German carp in the United States. Rept. U. S. Comm. Fish. 1904, pp. 523-641. Cooper, Edwin L. 1951. Validation of the use of scales of brook trout, Salvelinus fontinalis, for age determination. Copeia, 1951, No. 2, pp. 141-148. Cooper, Gerald P., and John L. Fuller. 1945. A biological survey of Moosehead Lake and Haymock Lake, Maine. Maine Dept. In- land Fisheries and Game, Fish. Survey. Rept. No. 6, 160 pp. Deason, Hilary J., and Ralph Hile. 1947. Age and growth of the kiyi, Leiirirhthi/f; kiyi (Koelz), in Lake Michigan. Trans, .\nier. Fish. Soc, vol. 74 (1944). Eschmeyer, Paul H., Russell Daly, and Leo F. Erkkila. 1953. The movement of tagged lake trout in Lake Superior. Trans. Amer. Fish. Soc, vol. 82, pp. 68-77. Farran, G. p. 1936. On the mesh of herring drift net.s in relation to the condition factor of the fish. Jour, du Cons., vol. U, pp. 43-52. Fish, Marie Poland. 1932. Contributions to the early life histories of sixty-two species of fishes from Lake Erie and its tributary waters. Bull. U. S. Bur. Fish., vol. 47, pp. 293-398. Ford, E. 1933. An account of the herring investigations con- ducted at Plymouth during the years from 1924 to 1933. Jour. Marine Biol. Assoc vol. 19, No. 1, pp. 305-384. Fry, F. E. J. 1949. Statistics of a lake trout fishery. Biometrics, vol. 5, pp. 27-67. 1953. The 1944 year class of lake trout in South Bay, Lake Huron. Trans. Amer. Fish. Soc, vol. 82 (1952), pp. 178-192. Fry, F. E. J., and W. A. Kennedy. 1937. Report on the 1936 lake trout investigation. Lake Opeongo, Ontario. University To- ronto Stud., Pub. Ont. Fish. Res. Lab., No. 42, pp. 3-20. Greeley, John R. 1934. Fishes of the Raquette Watershed, with annotated list. Suppl. 23rd -Ann. Rept. N. Y. Cons. Dept. In: A Biological Survey of the Raquette Watershed, pj). 109-135. 1936. Fishes of the area (Delaware-Susquehanna Watershed) with annotated list. Suppl. 25th Ann. Rept. N. Y. Cons. Dept. 1935, pp. 45-88. Hall, A. E., Jr., and Oliver R. Elliott. 1954. Relationship of length of fish to incidence of sea lamprey scars on white suckers, Calosto- mus commersoni, in Lake Huron. Copeia, No. 1, pp. 73-74. Hildebrand, Samuel F., and Louella E. Cable. 1930. Development and life history of fourteen teleostean fishes at Beaufort, N. C. Bull. U. S. Bur. Fish., vol. 46, pp. 383-488. AGE DETERMINATION FROM SCALES OF LAKE TROUT 59 Hii.DEBRAND, Samiel F., and LovELLA E. Cable. — Con. 1934. Reproduction and development of whitings or kingfishe.s, dnim.s, spot, croaker, and wcakfi.-ihes or sea trouts, family Sciaenidae, of the Atlantic Coast of the United States. Bull. U. S. Bur. Fish., vol. 48, pp. 41-117. 1938. Further notes on the development and life history of some teleosts at Beaufort, X. C. Bull. U. S. Bur. Fish., vol. 48, pp. 505-642. HiLE, Ralph. 1949. Trends in the lake trout fishery of Lake Huron through 1946. Trans. Amer. Fish. Soc, vol. 76 (1946), pp. 121-147. HiLE, Ralph, and Howard J. Buettner. 1954. Statistics of the lake troiit fishery of Lakes Huron, Michigan, and Superior, 1949-53. Great Lakes Fishery Committee. Minutes of Annual Meeting, St. Louis, Mo., pp. 36- 40. HiLE, Ralph, Pail H. Eschmeyer, and George F. LlNCER. 1951. Decline of the lake trout fishery in Lake Michigan. Fish. Bull. U. S. Fish and Wildlife Service, vol. 52, pp. 77-95. Hodgson, William D. 1929. Investigations into age, length, and maturity of the herring of the southern North Sea. Part in. The composition of the catches from 1923 to 1928. Min. Agric, and Fish., Fish., Invest. Ser. II, vol. 11, No. 7, 71 pp. Kennedy, W. A. 1954. Growth, maturity and mortality in the rela- tively unexploited lake trout, Cristivomer namaycush, of Great Slave Lake. Jour. Fish. Res. Bd. Canada, vol. 11, pp. 827-852. M ASSET, Frank J. 1951. The Kolmogorov-Smirnov test for goodness of fit. Jour. Amer. Stat. Assoc, vol. 46, pp. 68-78. Miller, R. B., and W. A. Kennedy. 1948. Observations on the lake trout of Great Bear Lake. Jour. Fish. Res. Bd. Canada, vol. 7, pp. 176-189. MiLNER. Ja.MES W. 1874. Report on the fishes of the Great Lakes; the result of inquiries prosecuted in 1871 and 1872. Rept. U. S. Comm. Fish.. 1872-1873, pp. 1-78. Moffett, James W. 1952. The study and interpretation of fish scales. The Science Counsellor, vol. 15, No. 2, pp. 40-42. Reibisch, Johannes. 1899. Ueber die Eizahl bei Plenronectes plalessa und die Altersbestimniung dieser Form aus den Otolithen. Wiss. Meers., Abt. Kiel, X. F., Bd. 4, s. 231-249. SCHNEBERGER, EdWARD. 1936. Tagged trout reveal new facts and figures. The Fisherman, vol. 5, No. 7, p. 1. Shetter, David S. 1951. The effect of fin removal on fingerling lake trout {Cristivomer namaycush). Trans. Amer. Fish. Soc, vol. 80 (1950), pp. 260-277. S.viith, Oliver H.. and John Van Oosten. 1940. Tagging experiments with lake trout, white- fish, and other species of fish from Lake Michigan. Trans. Amer. Fish. Soc. vol. 69 (1939), pp. 63-84. Van Oosten, John 1949a. The sea lamprey — a threat to Great Lakes fisheries. State Government, vol. 22, pp. 283-284, and 289. 1949b. Progress report on the sea lamprey study. The Fisherman, vol. 17, Xo. 3, pp. 6, 9, and 10. 1950. Progress report on the study of Great Lakes trout. The Fisherman, vol. 18, Xo. 5, pp. 5, and 8-10. and Xo. 6, pp. 5 and 8. Van Oosten, John, Ralph Hile, and Frank W. Jubes. 1946. The Whitefish fishery of Lakes Huron and Michigan with special reference to the deep- trap-net fishery. Fish. Bull. V. S. Fish and Wildlife Service, vol. 50, 1950, pp. 297-394. U. S. GOVERNMENT PRINTING OFFICE 1956 O — 378326 COMPARATIVE STUDY OF FOOD OF BIGEYE AND YELLOWFIN TUNA IN THE CENTRAL PACIFIC By JOSEPH E. King and Isaac I. Ikehara, Fishery Research Biologists The predominant species of tuna captured on longline-fisliing surveys of the Fish and Wildlife Service's Pacific Oceanic Fishery Investigations (POFI) are the yellowfin, Neothunnus macropterus (Temminck and Schlegel), and the bigeye, Para- thun?}us sibi (Temminck and Schlegel), with a catch ratio of about 5 to 1 in favor of the yellow- fin. These are large tanas, the yellowfin oc* casionally reaching a weight of 200 pounds and the bigeye a weight of 300 pounds in the tropical Pacific. The two species have a marked super- ficial resemblance in general body shape and coloration and arc not always differentiated in the commercial catch. Murphy and Shomura (1953a, 1953b), in dis- cussing results of experimental longline fishing conducted by POFI, point out interesting differ- ences in the distribution of these two species. In the tropical Pacific, the bigeye have been taken in greatest numbers north of latitude 5° N. The best catches of yellowfin, on the other hand, have been made in the general region of the Equator, sometimes to the north when the area is under the influence of southeast tradewinds, and some- times to the south when the northeast trades are dominant. Tliis shift in abundance that appears to be related to changes in the prevailing winds can now be explained, at least partially, from our knowledge of the ocean currents and their effect on the basic food supply (Cromwell 1953).' Al- though the peaks in abundance do not correspond exactly, tlie general area of high yellowfin catch is also the area of greatest zooplankton abund- ance (King 1954). The horizontal distribution of the bigeye, however, does not seem to conform to the general pattern that the most fish are found where food is most abundant. There is also some evidence of difference in the vertical distribution of yellowfin and bigeye. While the results are rather variable, there have ' .\Iso a manuscript by O. E. Sette: Nourishment of central Pacific stocks of tuna by the equatorial current system (Proceedings of the 8th Pacific Science Congress). been indications on certain POFI cruises to the equatorial area that the best catches of bigeye came from greater depths than those of the yellowfin (Murphy and Shomura 1953b). In Ha- waiian waters the bigeye occurs in greatest num- bers during the winter months from Octol)er to May, whereas the yellowfin is most abundant from May to September (Otsu 1954). Brock (1949) points out that the Hawaiian longline fishermen try to increase the catch of bigeye after the yellow- fin season by lengthening the hook lines in order to fish deeper. Also, unlike the yellowfin, the bigeye — at least the adults — are rarely taken by surface-fishing methods. Nakamura (1949) states that the bigeye is thought to occur at the deepest levels of any of the tunas. It appears that the bigeye prefers somewhat colder water than does the yellowfin, or perhaps the two species have different feeding habits or food preferences which influence their distribution. The purposes of this study are to describe the food of bigeye tuna in the central Pacific, to com- pare the foods of bigeye and yellowfin tuna - captured at about the same time and place, to determine whether differences occur which are associated with the horizontal and vertical distri- bution of these fish, and to obtain information on food preferences of each fish which maj^ be useful to the commercial fishery. The experimental fishing carried out by POFI has provided collec- tions of bigeye and yellowfin stomachs which are essentially alike in respect of time and area and which were obtained with standardized fishing methods. Therefore, we believe the resulting data should provide reliable comparisons of the food of these fish because these several variables have been controlled. There is an extensive literature, reviewed pre- viously by Reintjes and King (1953), dealing with the food of yellowfin, whereas there are only a very ' The food of yellowfln was previously described by Reintjes and King (1953). 61 62 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE few references pertaining specifically to the food of bigeye. Suyehiro (1942) desciibes this species as a very voracious fish and lists the following items as appearing in its food: amphipods, shrimp, cuttlefish, squid, sardines, sauries, bonitos, needle fish, and a viper fish. In the report of the South Seas Tuna Fishery Investigations for 1950 (,Kan- agawa et al. 1951), the food of 27 bigeye is shown to include the following: 7 squid, 1 octopod, 3 deca- pod Crustacea, 1 fan fish, 15 needle fish, 1 file fish, 6 pomfret, and 4 lantern fish. This suggests that the bigeye, like many other tunas, has a varied diet. A large number of the tuna stomachs reported on here were examined by John W. Reintjes, Sueto Murai, and T. J. Roseberry, former em- ployees of POFI. We appreciate their services in a difficult and generally disagreeable task. We are grateful to other staff members of POFI for assistance in handling these large fish aboard the vessels and in removing and preserving the stomachs. SOURCE OF MATERIALS This report is based on examination of 439 yellowfin and 166 bigeye stomachs collected on 11 cruises of Fish and Wildlife Service vessels during the years 1950 to 1953 (table 1). The yellowfin data include 125 stomachs collected in 1950 and 1951 and previously reported on by Reintjes and King (1953). These collections and the additional 314 yellow^n stomachs obtained in 1952 and 1953 were obtained at the same stations, or near the same stations, as furnished the bigeye stomachs included in this report. The sampling area (fig^ 1), extended along the Equator between M aufim^ 119° W. and 180° and approximately from lat- itude 17° N. to latitude 14° S. at its greatest width. The tuna were captured by longline at depths of about 150 to 500 feet. This method of fishing, as practiced by POFI, has been reviewed by Murphy and Shomura (1953a); the design and construction of the gear was described by Niska (1953). Only fish caught 25 miles or more from land are considered in this study ; therefore local differences due to reef faunas should be reduced to a mini- mum. The sampled fish varied widely in size, from 87 to 172 cm. fork length for the yellowfin, and from 77 to 196 cm. fork length for the bigeye (fig. 2). Weights of fish given in this paper were 180° 170° 160° 150° 140° 130° I2C ° 20'' ' o "t> O YELLOWFIN ONLY • • BIGEYE ONLY a YELLOWFIN 8 BIGEYE • i ► 10° 0° • 1 c c )0 o c o o o o * 3 9 • o* *f • ° q? o o » • 9 • C oc 8 • • 9 c c c o )0 o >o < o o » > 1 c ( t a » > k t a a c o o 10° (* o 20° — 10° 10° 180° 170° 160° 150° 140° 130° 120° Figure 1. — Locations of the stomach collections of yellowfin and bigeye tuna captured by experimental longline fishing in the central Pacific, 1950-53. FOOD OF BIGEYE AND YELLOWFIN TUNA 63 Table 1. — Distribution of yellowfin and bigeye stomachs collected from the central Pacific, identified by vessel, cruise, time of year, and locality Sampling area Yellowfin Bigeye Vessel Cruise No.— Period Range or longitude (W.) Range of latitude Xumber captured Number of stomachs exam- ined Percent of catch sampled Number captured Xumber of stomachs exam- ined Percent of catch sampled Hugh M. Smith Hugh M. Smith- _ 7 11 11 1 1 2 12 13 18 14 15 Oct.-Xov. 1950 Aug -Sept. 1951 157°-167'' ISOMse" 155°-180° IW-ISO" 140° ll°X-0° 15''X-»''S.... 5°X-7'>S 9°N-1°S e^N-S'N 6''N.-2''N---- 7°X.-5'>S..... 17°N.-5°S.... 9°N.-10°S-... 4°N.-14''S.... 10°N.-6° S.... 132 457 210 72 42 720 146 135 60 106 197 1 106 M53 59 44 19 1 55 40 69 20 80 34 28 61 17 3 1 41 67 65 10 22 93 30 43 11 60 28 29 50 19 46 14 36 6 17 2 13 5 10 17 19 27 64 John R Manning ,. Jan.-Mar, 1952 . 20 Charles H. QUbert Cavalieri May-June 1952 June-July 1952 Aug.-Sept. 1952 Aug.-Sept. 1952 Oct.-Nov. 1952 Oct.-Xov. 1952 Jan.-Mar. 1953 Apr.-June 1953 40 Cavalieri . . .- 140°-142'' 140°-150° isr-no" 120°-131° 140°-150° isflo-no" 22 John R. Manning John R. Manning Hugh M. Smith- -. John R. Manning John R. Manning 18 34 34 100 59 I Of this number, only 38 (29 percent of the catch) were considered comparable in respect to time and place to the bigeye collections and were included in this report. ' Of this number, only 87 {19 percent of the catch) were included in this report for the same reason as above. 1 — i — I — I — r YELLOWFIN 1 — I — \ — I — I — I — I — I — 1 — \ — r I r^^rT^^rrr . FORK LENGTH (CM ) BODY WEIGHT (LBS ) -1 — 1 — t — I — ' — I — I — I — I — I — r- BIGEYE 100 47 120 110 160 FORK LENGTH (CM ) 81 127 187 BODY WEIGHT (LBS ) 200 360 FiGiRE 2. — LeiiKth-frequeiicy distribution of yoUowfin and bigeye tuna from which stomach.s were collected. derived from length measurements converted by means of length-weight tables provided in the POFI Scientific Field Manual (unpublished). METHODS At sea, the stomacii was removed as soon as possible after the fish was captured, placed with any iTgui-gitaled material in an unbh'aclied-inuslin bag. and preserved in lO-peicent formalin. A label bearing date, species najme, fork length, fish- ing method, hook number, bait used, name of observer, vessel, and cruise number was placed with each stomach. Tuna landed with their stomachs everted were not sampled. The stomach was removed by one of the follow- ing methods: (1) The abdominal cavity was opened by a longitudinal midventral incision, the small intestine was severed posterior to the pyloric valve, and the stomach was freed by cutting through the esophagus; or (2) the gill membrane was slit along the line of attachment with the cleithrum posterior to the fourth gill arch, the viscera was pulled out, and the stomach was removed by cutting througli the small intestine and esopliagus. In the laboratory, the stomachs were soaked in fresh water for a period of 16 to 24 hours to remove excess formalin. Each stomach was then slit open, and the contents were carefully removed and separated into groups according to kind of organism. Identifications were made as com- pletely as was practicable, and the number of each species or group of organisms present was recorded. Each species or group was measured volumetrically by the displacement of water in a graduated cylinder of appropriate size. Bait used to capture tlie tuna was omitted from this analysis. The methods and literature used in the identification of the food organisms were essentially the same as that employed bv Reintjes and King (195.S) and will not be I'eviewed here. Berg's (1947) system of classification and nomen- clature was primarily useii foi' the family names of tlie forage fishes. 64 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE A detailed list of the food organisms found in the tuna stomachs is presented in the appendix (table 11). For each kind or group of organisms there are shown (1) the total number of sucli organisms, (2) the number of stomachs in which they occurred, (3) the percentage of occurrence, (4) the total aggregate volume of each food element, and (5) the percentage of total volume. Regardless of the method or methods of anal- ysis used, there are many uncontrollable variables inherent in food studies which detract from the precision of the results. It is our belief, however, that for a fish with a generalized diet, such as that of the tuna, any of the commonly used meth- ods of evaluation will give substantially the same results if a sufficiently large number of specimens are examined. In reporting the results of our studies on tuna food we use both the percentage- of-occurrence and the percentage-of-volume meas- urements (as described by Reintjes and King 1953) and the average volume of food per stom- ach. The food items that rank liigh in number, volume, and frequcncv of occurrence are most likely to be important foods. No attempt has been made to apply statistical tests of significance to the data. It is likely tliat the variates used — volume of food per stomach, percentage of occurrence, and percentage of total volume of the organism — are not distributed nor- mally and that the means are correlated with the variances or standard deviations. To apply meaningful tests of significance, transformation of the data would be necessary. Moreover, several of the comparisons that will be made involve two-way or three-way classification of the data. Even if suitable transformations were derived, the application of advanced analysis of variance techniques would be hampered by unequal subclass numbers. Furthermore, it appears that in both yellowfin and bigeye there is an increase in mean volume of food per stomach with increase in size of fish. ^ \\^ ^ » * f ■* i 9"' ^■■ h Fir.URE 3. — Exainple.s of type.s of food commonly found in .stomach.s of yellowfin and bigeyf tunas: Left to right: pom- fret (1), truncated .sunfi.sh (1), snake mackerel (1), lancet fish (1), shrimps (3), viper fish (15), hatchet fi.sh (3), euphausids (8), juvenile stomatopods (3), crab megalopa (12), squid (3), and paper nautilus (1). 10 9 - I C3 e UJ » 7 >- o o 6 m ii o b m _] 4 CC Ul 0. 3 ,^ (> o d -I o > FOOD OF BIGEYE AND YELLOWFIN TUNA YELLOWFIN BIGEYE 65 1200 ' 1 1 1 I 1 - MOO - (A) - 1000 - - 900 - - STOMACH 8 § — • - IT 600 UJ a. — - 500 o o ~ 400 _i o - • - ^ 300 - — 200 - j^L-^ _____ - 100 A 'l :-:l:v-.J,'V1^S:;;^i.-: • .■(•■ 1 T T T T (A) ^ :■■■■■■ -f • • -i-:- (B) "1 r "1 r (B) - 40 280 320 360 80 120 160 200 240 40 80 120 160 200 240 BODY WEIGHT (LBS) BODY WEIGHT (LBS) Figure 4. — Regressions of (A) food volume per stoniacli and (B) food volume per unit body weight on total body weight for 439 yellowfin and 166 bigeye captured on longlines. and tliere is also a decrease in average stomaeli content per unit of body weight (cc./lb.) with increase in size of fish. Tlie least-s(itiares trend lines shown in figure 4 (tliere is no a priori reason for assuming rectilinearity) indicate tlH> need for covaiiance nu'thods of statistical analysis, again after stiitahie liansformations. Finally we must point out the great variability of the data as illustrated by the wide scatter of points about tiie trend lines. This gi-eat variability reduces the opportunity- of denionstrMting stat ist icidly signifi- cant differences, particularly when the data are analyzed in subgroups which contain few speci- mens in each. Because of the difficidties outlined above, in the following sections we have tabulated average values and have discussed difi'crences and trends without attempting to ajjpraisc their statistical significance. Consequently, the inferences that we make must be regarded as suggestions oidy. They may form the bases for hypotheses which can be tested more stringently in the futuic. 66 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE RESULTS The food of both the yellowfin and the bigeye was primarily fish, of great variety, and squid (table 11, Appendix). Other mollusks, such as the argonauts and octopods, and crustaceans were of minor importance.^ Figure 5 ilhistrates the percentage of occurrence of the major food items. Figure 6 shows the percentage of aggre- gate total volume of each major food element, which indicates its relative importance by bulk. Representatives of 48 fisli families and 1 1 invertebrate orders were found among the stomach contents of the yellowfin, as compared with 36 fish families and 9 invertebrate orders for the big- eye* Despite this great variety in the food, only OTHER FOOD Figure 5. — Percentage of occurrence of the major food elements. s Among the results of this study, not referred to elsewhere in the report but perhaps worthy of mention, were observations on the number of stomach parasites. Among the bigeye, 26 percent of the stomachs examined were Infested with nematodes and 32 percent with trematodes. The infestation was somewhat less among the yellowfin, being 16 percent for nematodes and 26 percent for trematodes. * The greater variety in the food of the yellowfin as compared with the big- eye is due, we believe, simply to the fact that more than twice as many yellow- fin stomachs were examined. a few items were of primary importance to either species. For both the yellowfin and the bigeye, those food elements ranking high in number, volume, and frequency of occurrence were squid, of the families Ommastrephidae and Loliginidae, and among the fish the pomfret {CoUyhus drachme) and snake mackerel {Gempylus serpens) were important. Certain fishes, such as the tunas (Thunnidae) and the sun fishes (Molidae), were relatively important in volume but ranked low in number and frequency of occurrence, indicating that they are only occa- sionally utilized. Crustacea of the order Stomato- poda, prominant in number in the food of yellow- fin, were completely lacking from the bigeye stomachs. The young of other tunas, especially skipjack, formed a much more important part of the yellowfin diet than that of the bigeye. In the following sections of this report we shall try to describe the major differences and similarities in the foods of these two species of tuna as related to such factors as size of the tuna, area and depth of capture, season, and features of the equatorial- current system. Variation in Food with Size of Tuna In general, for both yellowfin and bigeye, there was an increase in food volume per stomach with an increase in size of the tuna (fig. 4). With the hope of minimizing the effects of this factor, in our examination of differences in the food specif- ically related to size of tuna we have split the data for both species into two size groups, (1) those less than 140 cm.^ and (2) those 140 cm. and over, in fork length (table 2). This provided for each species two groups of fish roughly equal in number. In the yellowfin the larger size gfoup contained 29 percent more food per stomach, and in the bigeye it contained 16 percent more. The ratios of stomach content to body weight are almost identical for the two species (table 2). Although Crustacea make up a very small per- centage of the food of these large, deep-swimming fish, in both species tlie smaller specimens con- sumed greater amounts of such organisms as crab larvae, shrimp, and ampliipods. In both species, the larger specimens consumed less fish and more mollusks — as percentage of total volume — than did the smaller size group; this was particularly true for the bigeye. The per- ' A 140-cm. yellowfin from the equatorial Pacific weighs approximately 118 pounds, while a 140-cm. bigeye weighs approximately 127 pounds. FOOD OF BIGEYE AND YELLOWFIN TUNA 67 ^fi-'f-'-"'^ S- ^^ YELLOWFIN BIGEYE FifiiRE 0. — Comparative importance, in volume, of the major food elements. centage by occurrence and percentage by volume for the fish famihes prominent in the diet exhibited little variation with the size of the tuna. Variation in Food with Depth of Capture Figure 7 is a diagram of one unit (a basket) of POFI longline gear, showing the arrangement of hook-bearing dropper lines and the general lay of the line with respect to the surface. Although an attempt is made to set the line at each station in a standard fashion, with an average distance be- tween buoys of about 900 feet, the actual depth of fishing is quite variable depending upon the amount of sag in the main line, which is gi-eatlv influenced by wind and current conditions. FiriiRK 7. — .Arrangement of a unit (ba.sket) of POFI standarfi loMKlinc gear showing the float lities, main line, hook-bearing dropper lines, and the general lay of the line with respect to the surface. :{887:)4 ( ) — Sft 2 Murphy and Shomura (1953a) have calculated that the ma.ximuin possible depth for hooks 1 and 6, with a 900-foot buoy interval, is 310 feet; for hooks 2 and 5, it is 450 feet; and for hooks 3 and 4, it is 530 feet. These maximum depths are seldom achieved, however, because of the rela- tively strong surface currents generally prevailing in this region. The miniminn depths are even more uncertain; therefore it is difficult to define a depth range for each of the hooks. We postulate that liooks 1 and 6 may fish at depths of 1.50 to 300 feet, hooks 2 and 5 at depths of 250 to 400 feet, and hooks 3 and 4 at depths of 300 to 500 feet. Despite this variation and the imcertain- ties involved, it is worthwhile, without attempt- ing to designate actual fishing depths, to make comparisons between tlie shallow (hooks 1 and 6), intermediate (hooks 2 and 5), and deep (hooks 3 and 4) levels of capture with respect to dift'erences in stomach contents. Because of tlie rather slight differences in composition of tlie food associatetl with the size of the tuna, the two size groups (140 cm.) were combined for liiis study. Table 3 shows the variation in composition of stomach contents with igeye stomachs were collected at 0-24 miles, and few (eigiit) were collected in the 25-99 mile interval; tlierefore, the data do not provide the desired information on difterences in the food related to this feature. There was some indica- tion that the consumption of squid and pomferts by the bigeye increased in an offshore direction, as compared with tlieir uniform utilization by the FOOD OF BIGEYE AND YELLOWFIN TUNA 69 SQUID FISH 100 90 80 - w 70- UJ 2 I- 50 z UJ " 40 o 30 ID 3 O 20 10 O 100 YELLOWF (109) (120) (165) i- A 90 - 80 70 60 UJ Z I- 50 z UJ <-> 40 u 5 30 o 20 10 BIGEYE (18) (45) SHALLOW INTERMEDIATE DEEP FinuRE 8. — Variation in the major food categories (total fish and squid) as related to the depth at which the tuna were captured. Number of stomachs is shown in parentheses. yellowfin (tahlp 4), and in the bigeye the average food vohune increased with greater distance from land while in the yellowfin the volume varied irregularly. Variation with Season and Longitude To examine differences related to time of sampl- ing, the various cruises were grouped into four seasonal periods, as indicated in table 5. For botii species the largest average volume of food occurred in the April-July period, with ()ctob(>i- Xovember averaging the lowest in the yellowfin and August-September the lowest in the bigeye. If we consider the average volinnc per stomach of the major food elements, we find tlial, in our samples of both tunas, fish were consumed in greatest amount during April-.Tuly and in least amount during August-September (fig. 9 and table 5). The average volumes of squid and the major fisli families represented in the food did not vary in parallel fashion for thebigeyeandyellowfin. When the data from the various cruises are combined with regard to longitude but witliout regard to time of year, we obtain the results pre- sented in table 6, with the variation in availability ^ SQUID TOTAL FISH I80'>-I55"' 1 50<^ 140° WEST LONGITUDE 1 30°- 1 20° /<-■ FiciRE * — Variation in the major foods as related to time of year that the tuna were captured. Number of stomachs is shown in pareiithe.ses. 70 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE Table 3. — Variation in volume and composition of stomach contents with depth of capture of yellowfin and bigeye tuna Food organisms Average volume (cc.) per stomach Percentage of occurrence Percentage of total volume Shallow Inter- mediate Deep Shallow Inter- mediate Deep Shallow Inter- mediate Deep Crustaceans: 1.8 0.7 26.6 47.2 11.8 0.8 47.4 43.2 9.0 5.3 5.3 4.4 10.6 0.0 1.0 5.0 1.8 0.0 0.6 0.0 88.1 91. 9 0.7 1.4 30.7 63.9 5.4 0.9 54.9 86 7 10.8 22.5 6.7 22.7 14.4 0.5 0.4 6.0 4.4 3.4 0.4 0.3 92.2 153.3 1. 1 3.2 33.7 36.0 7.4 6.9 78.6 83.7 13.4 21.1 9.0 14.5 22.2 2.5 0.3 3.6 12.8 1.4 0.9 0.1 121.7 129.9 39.4 33.3 84.4 72 2 47.7 33.3 91.7 72.2 53.2 27.8 33.9 33.3 9.2 0.0 11.9 11.1 1.8 0.0 27.5 5.5 44.2 35.6 90.0 84.4 49.2 17.8 91.7 86.7 64.2 26.7 35.0 42.2 9.2 2.2 4.2 17.8 1.7 4.4 23.3 8.8 46.7 46.9 90.3 83.9 37.0 40.7 93.9 86.2 66.7 35.8 33.9 39.6 9.1 2.6 7.3 22.2 2.4 1.2 27.3 7.4 2.0 0.7 30.2 51.4 13.5 0.8 53.8 47.0 10.2 5.8 6.0 4.8 12.0 0.0 1.2 5.5 2,0 0.0 0.6 0.0 0.8 0.9 33.3 41.7 6.8 0.6 59. 5 56.5 11.7 14.7 7.3 14.8 15.6 0.3 0,4 3.9 4,8 2.2 0,6 0.2 9 Bigeve 2 5 Squids: Yellowfin 27 7 Bigeye _ ... 27 7 Other mollusks: Yellowfin 6 1 Fish (total): Yellowfin . . . 64 6 Bramidae: Yellowfin ....... . 11 Bigeye Oempylidae; Yellowfin .. . _. 16.3 7 4 11 2 Thunnidae: Yellowfin 18 2 1.9 Sudidae: Yellowfin 2 ■» 7 Molidae: 10 6 1 1 Other foods: OS 0,0 All foods: Yellowfin Number of stomachs examined- Yellowfin 109 18 141 152 120 162 0.7 0.6 120 45 140 148 118 148 0.8 1.0 166 81 142 142 122 133 1.0 1.0 Bigeye Average fork length (cm,): Bigeye __ Average weight (lbs.): Yellowfin . Average volume (cc.) food per pound of body weight: Yellowfin FOOD OF BIGEYE AND YELLOWFIN TUNA 71 Table 4. — Variation in volume and composition of sto/nach contents with distance of place of capture from nearest emergent land Food organisms Average volume (cc.) per stomach Percentage by occurrence Percenuge of total volume 25-99 miles 100-399 miles 400 mi. and over 25-99 miles 100-399 miles 400 mi. and over 25-99 miles 100-399 miles 400 mi. and over Crustaeeans: Vellowfin 1.2 3.7 30.7 9.8 1.2 3.0 79.2 28.0 14.7 1.5 4.8 21.9 1.6 0.0 0.7 3.7 38.2 CO 1.1 0.7 11.3. 4 46.1 1.8 1.9 24.2 17.9 4.4 2.2 52 1 94.0 9.5 15.0 5.8 18.5 5.9 10.8 0.6 5.1 9.6 4.2 0.8 0.2 83.9 116.2 0.4 2.5 34.8 64.2 11.1 5.5 71.1 81.5 12.4 30.7 8.0 12.2 25.5 2.4 0.3 3.1 6.0 0.0 0.3 0.1 117.9 153.8 53.3 75.0 90.0 75.0 13.3 25.0 96.7 62.5 43.3 25.0 36.7 12 5 10.0 0.0 10.0 12.5 6.7 0.0 26.7 12.5 52.7 42 8 89.6 76.2 36.8 34.9 94.5 85.7 61.7 25.4 31.8 38. 1 .VD 3.2 10.4 17.5 3.0 4.8 32.8 6.3 7.7 35.8 84.1 87.4 48.1 30.5 90.9 85.3 62 3S. 9 31.2 38.9 11. 1 3.2 2.9 16.8 1.9 0.0 15.4 6.3 1.1 8.2 27.1 21.7 1. 1 6.6 69.8 62.0 13.0 3.4 4.2 48.6 1.4 0.0 0.6 8.2 33.7 0.0 1.0 1.5 2.2 1.7 29.0 15.4 5.3 1.9 62.5 80.9 11.4 12 9 6.9 15.9 7.0 9.3 0.7 4.4 11.5 3.6 1. 1] U. 1 0.4 1.6 Squids: 29.6 41.8 Other mollusks: 9.5 3.6 Fi5h (total): Yellowfin - 60.3 53.0 Bmmidae: Vellowfin 10.5 20.0 (Jeinpylidae: 6.8 7.9 Thunnidae: Vellowfin - - --- - - 21.7 1.5 Sudidae: 0.3 2 Molidae: 5.1 0.0 Other foods; 0.3 0.0 All foods Number of stomachs: 30 8 138 153 112 166 1.0 0.3 201 63 140 139 118 125 0.7 0.9 208 95 142 148 123 149 1.0 1.0 Bigeve .\veraBe fork length (cm.): Yellowfin .Average weight Obs.): Average volume (cc.) food per pound of body weight: Bigeye ... 1 1 72 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE Table 5. — Variation in volume and composition of stomach contents with time of year at which the tunas were captured Food organisms Average volume (cc.) per stom- ach Percentage by occurrence Percentage of total vo ume Jan- March April- July Aug.- Sept. Oct.- Nov. Jan.- March April- July Aug.- Sept. Oct.- Nov. Jan.- March April- July Aug.- Sept. Oet.- Nov. Crustaceans: Vellowfin 1.1 1.9 27.0 21.8 7.9 3.2 56.9 109.5 8.0 29.1 8.1 11.5 10.4 0.2 1.4 34.4 72.4 14.5 3.9 105.7 116.4 14.9 51.8 8.0 16.9 25.7 4.9 0.2 2.6 32.9 3.0 0.3 0.03 155.2 194.1 0.6 1.1 40.3 40.3 4.5 5.6 52.0 51.4 14.1 4.5 1.9 8.0 25.1 0.0 2.2 0.2 0.3 0.2 97.7 98.7 2.1 5.3 21.1 30.9 5.4 2.9 54.8 76.2 10.8 12.8 8.6 24.3 5.2 16.6 0.5 1.8 14.7 3.0 0.8 0.1 84.1 115.3 60.1 48.0 94.5 80.0 46.9 48.0 96.1 92.0 60.1 24.0 45.3 48.0 7.8 13.3 36.0 0.0 43.7 12.0 26.8 37.0 76.0 78.3 47.9 30.4 91.5 89.1 50.7 43.5 23.9 37.0 16.9 6.5 7.0 19.6 12.6 2.2 9.9 6.5 29.9 25.9 96.3 86.1 39.3 13.0 90.7 70.3 69.2 33.3 24.3 28.0 5.6 0.9 5.6 0.9 7.5 3.7 43.6 48.8 91.0 92.7 21.0 26.8 97.0 95.2 60.9 31.7 28.6 39.0 5.3 4.9 5.3 12.2 2.3 4.9 25.6 9.8 1.2 1.4 28.8 16.0 8.4 2.3 60.6 80.2 8.5 21.3 8.7 8.4 11.1 1.0 9.5 0.0 0.9 0.2 0.1 0.7 22.2 37.3 9.3 2.0 68.1 60.0 9.6 26.7 5.2 8.7 16.6 2.5 0.1 1.3 * 21.2 1.6 0.2 0.02 0.7 1.1 41.2 40.9 4.7 5.6 53.2 52.1 14.4 4.6 2.0 8.1 25.7 0.0 2.2 0.2 0.3 0.2 2.4 Bigeve . _ 4.6 Squids: Yellowfin 25.1 Bigeye — Other mollusks: Yellowfin . .. 26.8 6.4 2.5 Fish (total) : 65.1 Bigeye 66.0 Bramidae: 12.9 Bigeye 11. 1 Gempylidae: Yellowfin 10.2 21.4 Thunnidae: Yellowfin . 6.2 14 4 Subidae: 0.9 13.0 0.0 0.6 1.5 Molidae: Yellowfin - 17.5 2.6 Other foods: 0.9 0.2 93.8 136.6 0.9 0.08 All foods: Number of stomach examined: Yellowfin 128 25 140 148 119 148 0.8 0.9 71 46 141 141 121 129 1.3 1.5 107 54 140 149 116 151 0.8 0.7 123 41 141 146 120 142 0.7 0.8 Bigeye Average fork length (cm.): Vellowfin Bigeye . - . Average weight (lbs.): Yellowfin Average volume (cc.) food per pound of body weight: Bigeye FOOD OF BIGEYE AND YELLOWFIN TUNA 73 V7?i SQUID I TOTAL FISH olOO S o (- f 75 a. UJ a. o 50 150 5 100 < z o YELLOWFIN (71) (128) (107) (123) ^ 1 I ^ i 25 BIGEYE (25) (46) i i (41) (54) I I -JUL AUG- SEP SEASON OCT -NOV Figure -KT — Variation in the major foods as related to the general longitude of capture of the tunas. Number of stomachs is shown in parentheses. of the major food items shown in figure 10. The chief simihirity between the two species lies in the lower volume of total fish in the food of tunas captured in the region of 140°-150° W. longitude. The utilization of squid, Bramidae, Gempylidae, and TluHinidae does not vary in any regular pattern for the two species. A majority of the Thunnidae appearing in the food of yellowfin captured in the area of 120°-130° W. were Auxis ^Aojo/y/, which was not prominent in the food in the more western regions and which in the l)igeye was represented by only one specimen, also from the 120°-13n° \V. region. P^or both bigeye and yellowhn, the largest specimens were captured in the eastern region (120-1:50° W.) and the smallest in the western region (155° W-180°). When the variation in volume of stomach contents is considered in terms of imit volume per iniit of body weight, we find 388734 O- 56 3 only slight regional diflferences for the yellowfin but a rather large variation for the bigeye (table ()). \w the bigeye, specimens from the western region contained 1.5 cc. of food per pound of body weight, as compared with 0.6 cc. for specimens from the central region and 1.0 cc. for specimens from the eastern region. These three values closely parallel the corresponding average volumes of total fish per stomach (115.3, 55.4, and 95.8 cc). Variation with the Current System The general pattern of the Pacific equatorial- current system has been described by Sverdrup and associates (1942, pp. 708-712). In brief, the major surface currents of this region are the North and South Equatorial Currents flowing toward the west, with the eastward-flowing Equatorial Coun- tercurrent sandwiched in between. Although the width of the Countercurrent (CC) may vary with longitude and season, its southern and northern boundaries are ordinarily near latitudes 5° X. and 10° X. in the Central Pacific. The South Eqiuitorial Current (SEC) is therefore on both sides of the Equator, while the North Equatorial Current (NEC) is confined entirely to the Xorthern Hemisphere. The prevailing east to southeast tradewinds, together with the Coriolis force resulting from the earth's rotation, induce a divergence of the surface waters at the Equator that is accompanied by up- welling. Under certain conditions, described by Cromwell (1953) a convergence may be formed, between the Equator and the southern boundary of the CC, which, we hypothesize, may tend to concentrate plankton and, consec|uently. the tinia forage organisnis. Over the range of latitude sampled (17° X".- 14° S.), there are therefore certain natural sub- divisions of the environment that may be estab- lished on the basis of the features mentioned above. These may be defined as follows: (1) The XEC from the northern limit of our sampling (17° X.) to the northern boundary of the CC; (2) the CC, with its boundaries determined at the time of each crossing from vertical temperature sections;' (3) a zone of convergence in the SEC extending — accoril- ing to our definition — from the southern boundary of the CC to latitude 11^° X.; (4) a zone of diver- gence or upwelling in the SEC along the Equator from latitude 1J^° X. to latitude \)^ ^^ i ^ 5 SEC 4 DIV CONV AREA 2 CC FinuRE 11. — Variations with the current system in (A) yellowfin and bigeye catch on longline gear, (B) average volunie of food per stomach, and (C) average volume of food per pound of body weight. Boundaries for each di- vision of the current .system are defined in the text. Part A i.s derived from cruises 7, 11, and 18 of the Iltiiih M. Smith, cruises 11, 12, 13, 14, and 15 of the John If. Mann- ing, cruise 1 of the Charle.<; II. Gilbert, and cruise 1 of the Cavalieri. Xumberof ob.servations, as stations fished (part A) or .stomachs examined (parts B and ('), is shown in parentheses. volume of stomach contents.' The divergence zone at tlie Equator produced good catches of yellowfin, but these fish contained the lowest food volumes. On the basis of both the average volume of food per stomach and the average volume of food per pound of l)ody weiglit — disregarding the three stomachs collected from the NEC — we judge that the yellowfin captured in areas 2, 3, and 5 were equally well fed. In the bigeye, there is a suggestion of parallel variation in catch rate and volume of stomach contents. This species was tlie best fed in areas 1 and 2, which were also the areas of best catch. The bigeye from near the Equator (area 4), where catches were poorest, con- tained the lowest food volumes. Table 7 illustrates variations in certain food components as related to the system of currents. The consumption of Crustacea by yellowfin is rougldy in accordance with the varying abundance of zooplankton as determined from oiu' plankton surveys (King and Demond 1953, King 1954). Tiieir utilization l)y l)igeye is quite different, iiowever, and may be related to differences in the kinds of organisms involved. In tlie food of yellowfin, for example, the crustacean fraction was principally amphi|)ods, with isopods and crab larvae of some importance; the bigeye had fed chiefly on shrimp and euphausids. The complex variations in the consumption of squid, Bramidae (chiefly Collijbu-y drachme), Gempylidae (chiefly Gempylus serpens), and total fish are difficult to understand, since we lack information on the lati- tudinal variations in abundance of these forage organisms. We should like ne.xt to exan)ine in greater detail the differences between the CC (urea 2) and the convergent zone (area 3) with respect to volume and composition of food utilized as related to deptli of capture of the tinias. As previously stated, the CC is a region of relatively good catch for l)igeye and of poor catch for yellowfin. Bigeye from this region contained about 50 percent more food in their stomachs than did the yellowfin, but they averaged somewhat larger in body size. • It was previously reported (Reiiiljes :iiicl Kiiiix I9.i:t) thai on one eniisc (eruise n, Hugh \f. Smith) there was some iiuliealion that for yellowfin the average volume of stomaeh contents varied directly with the ("ateli rate. 76 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE Table 7. — Variations in average volume per stornach of the major food categories as related to the current system (Boundaries of each area or division of current system are defined in text; volume is measured in cc] Food organisms Area 1, NEC Area 2, CC Area 3. Conv. Area 4, Div. Area 5, SEC Crustaceans: Yellowfin - - - 0.3 2.1 38.0 73.1 2.7 1.3 64.9 75.4 8.5 41.0 8.1 6.9 20.2 3.5 0.6 3.3 30.7 32.3 12.5 8.1 62.2 82.6 16.4 22.5 4.2 18.1 18.3 2.9 1.8 33. 1 29.2 4. 1 0.7 44.0 45.6 6.6 0.6 5.0 11.7 16.6 0.8 0.1 34.3 38.9 3.8 Squids: 16.6 11.9 Other molluslts: 6. 1 7.1 8.0 155. 7 0.7 5.0 4.0 37.2 1.4 Fish (total): 91.6 80.6 Bramidae: 9. 1 5.4 Gempylidae: 12.8 16.5 Thunnidae: Yellowfin - - . - -- - 1.5 28.3 Sudidae: 0.2 5.7 1.2 0.1 1. 1 1.3 0.6 1.6 2.5 10.9 Molidae: 44.6 5.2 6. 1 Other foods: 0.2 5.7 0.2 106,6 126.4 0.7 0.1 84.8 77.3 0.9 0.3 All foods: 42 3 201.9 106.6 152.0 115.3 97.9 Number of stomachs examined; 3 24 147 149 138 153 0.3 1.3 86 58 136 146 108 143 1.0 1.1 164 47 141 145 119 139 0.9 0.9 98 14 144 153 129 164 0.7 0.5 88 23 140 138 Average weight (lbs.): 118 Bigeye - - 120 Yellowfin - 1.0 Bigeye - -- . . . ._ 0.8 On the basis of average volume of food per pound of body weight there was little difTerence between the two species. The region of convergence has yielded the best yellowfin catches but has produced consistently poor bigeye catches. In this region the bigeye had about 20 percent more food in their stomachs than did the yellowfin, but the bigeye were also larger in average body size. Again the two species were almost identical with respect to average volume of food per pound of body weight. In the CC, tlie thermocline occurs at shallow to moderate depths, while in the convergent zone it lies much deeper. Accompanying changes in the deptli and velocity of the surface currents may greatly affect the fishing depth of the longliiie. In the region of sliallow thermocline it is possible that, as a result of the streaming of the line caused by the marked sliear between the moving surface waters and the relatively quiet waters below the thermocline, all hooks may be fishing at about the same level (Murphy and Shomura 1953b), and no marked difference might be expected in the food between the various hook levels. In a region of deep tliermocline the longline can hang vertically and lie entirely within the homogenous surface layer. A marked difference in hook depth and possible differences in the stomach contents of the catch may then result. Data have been assembled in table 8 and figure 12 to illustrate the variations in average volume per stomach for the major food categories with deptli of capture of the tanas in these two ocean areas. In the CC there is greater change in the food of yellowfin with depth than in the convergent zone; this is evidenced by a consistent increase with deptli, in the CC, in the utilization of Bramidae, Gempylidae, and total fish. In the bigeye the only important and consistent variation shown in the CC is a marked increase with deptli in the amount of Crustacea eaten and a decrease in the importance of Gempylidae, as contrasted with FOOD OK BIGEYE AND YELLOWFIN TUNA 77 ^YELLOWFIN BIGEYE 160 I u < Z O 120 ui 80 P 40 UI Z y- z 1^120 CD 3 100 O CRUSTACEA i _a SQUID I 80 - 60 TOTAL FISH i HOOKS CONV CC CONV , IL _ _^ 186 2 85 CC SHALLOW INTERMEDIATE CONV CC 384 DEEP i 4 I «| J I i J i CC ALL DEPTHS COMBINED FioiRE 12. — Variations in average volume per stomach of the major food categories with depth of capture of 250 yellowfin and 105 bigeye tuna taken by longline in the C'ountercurrent and the convergent zone. the increase with deptli in Gempyhdae as noted for yellowfin. In the convergent zone there is a similar increase with depth in the utilization of Crustacea and Bramidae. The major foods are of about equal importance in both areas. There is no indication that the tunas have one set of foods in the CC and another in the converfient zone. Tlie main difference between the two species is the much greater consumption of Crustacea by the bigeye in both the CC and tlie convergent zone. If we may con- sider the longline catch rate as an index to abun- dance, it would appear that the bigeye responds in a different manner than the yellowfin to the more favorable foraging conditions whicli, we hypothesize, e.xist in tiie convergent zone. OTHER VARIATIONS IN VOLUME OF STOMACH CONTENTS ^\^len the stomach-content volumes are clas- sified according to an arbitrary scale, the results (table 9) indicate for both species a rather low percentage of empty or near-empty stomachs; the average stomach contained a relatively small amount of food. This may mean that feeding is almost continuous, as contrasted with an irregular or spasmodic feeding habit, and that these fish have a high rate of digestion. For instance, it is hard to believe that a food volume of less than 100 CC, which was found in more than 50 percent of the stomachs (table 9), constitutes a daily or even semidaily ration for these large active fish. Unfortunately, our food studies provide no in- formation on rate of food consumption or digestion. In longline fishing, the gear is ordinarily set at daybreak and is hauled in during the afternoon. The time of landing is known, but not the time that the fish took the hook. On some cruises, 50 percent or more of the tuna are dead when landed. One might assume that these fish hail been on the line for a longer period of time than the fish that were landed alive. On the basis of this hypothesis we examined the records from certain cruises for which we had the greatest number of observations supplying information on condition when landed. These data, as summarized in table 10, seem to indicate that the fish that were dead when landed contained larger volumes of food, on the average, than those that were landed alive. Although we cannot satisfactorily explain this difi"erence, we believe that it may be related to the tendency for more dead fish to occur on the deep hooks than on the liooks fishing at shallow and intermediate depths; and in the yellowfin, at least, we have found an increase in volume of stomach contents with depth of capture (table 3). A combination of these factoi-s might produce the results shown in table 10. 78 IISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE Variations in average volume of food per stomach in pelation to depth of capture, comparing yellowfin and bigeye tuna taken by longline in the Countercurrent and convergent zone Table 8. [Organisms making up less than 1 percent of the total food volume for each depth category were omitted from table; volume is measured in cc] Convergent zone Countercurrent Yellowfin Bigeye Yellowfin Bigeye Food organisms Hooks 1 and 6 (shal- low) Hooks 2 and 5 (inter- medi- ate) Hooks 3 and 4 (deep) Hooks 1 and 6 (shal- low) Hooks 2 and 5 (inter- medi- ate) Hooks 3 and 4 (deep) Hooks 1 and 6 (shal- low) Hooks 2 and 6 (inter- medi- ate) Hooks 3and^ (deep) Hooks 1 and 6 (shal- low) Hooks 2 and 5 (inter- medi- ate) Hook.'i 3 and 4 (deep) Crustacea (total) ._ 0.6 0.6 0.8 0.5 2.1 4.3 4.2 28.4 1.7 2.9 3.7 0.1 0.5 0.3 0.1 0.6 3.1 2.6 Squids (total) 25.5 27.6 39.4 9.2 47.7 52.1 37.4 46.5 110.0 138.5 47.8 Loliginidae: 1.8 4.6 12.3 '"'i.'i 2.8 18.0 43.0 39.6 4.9 11.0 14.6 3.1 20.1 5.2 2.5 1.3 Enoploteuthidae: 1.2 3.3 2.1 1.8 1.9 3.4 7.1 5.5 Omniastrephidae: 5.5 7.3 4.6 2.0 2.1 5.1 5.0 8.8 5.0 7.3 2.9 1.4 3.6 3.4 2.9 8.1 103.1 17.6 4.5 Cranchiidae: 12.0 14.3 2.0 8.4 2.3 15.4 10.6 2.1 0.9 12.3 7.5 1.9 2.5 1.4 3.3 1.5 2.6 1.5 1 1 Argonautidae: 1.6 10.3 54.7 1.0 3.5 53. 8 1.2 74.2 0.9 12.9 1.6 68.0 1.1 Fish (total) 32.5 114.6 70.0 1.2 2.7 0.6 1.8 0.5 111.9 73.3 107.9 60.7 Sternoptychidae: 9.7 Unidentified Sternoptychidae 0.6 9.0 3.6 1.1 Sudidae: Unidentified Sudidae 26.3 4.2 2.1 Exocoetidae: 1.7 0.1 3.4 1.4 3.6 „fU*iJf i^Mm) 2.0 1.2 Carangidae: 1.8 2.4 2.4 15.3 1.1 1.0 Bramidae: 10.1 1.4 2.6 8.5 4.6 0.4 3.5 8.2" 1.3 9.9 14.9 7.7 4.0 12.4 4.1 0.6 61.7 4.5 1.4 17.9 4.6 3.5 2 4 1.3 Gempylidae: 2.0 1.2 1.3 1.7 5.2 1.3 ' " 0.6 39.0 4.2 0.4 2.3 0.1 1.2 4.3 1.0 15.5 3.2 9.5 9.5 9.5 0.4 2.3 Unidentified Gempylidae . .... 2.9 Nomeidae: 0.8 8.1 4.4 12.8 15.8 4.2 1.1 28.2 41.1 6.4 9.2 0.3 1.0 Echeneidae: 1.4 0.9 0.3 3.8 0.8 0.2 1.2 0.2 Balistidae: 4 3 0.8 Ostraciidae: 1.9 2.3 3.3 0.7 1.3 Molidae; Fanzania sp Other foods 4.0 0.5 95.6 6.8 1.7 0.6 161.9 0.4 90.8 0.8 130.4 '42.2 0.7 166.0 0.1 All foods 115.3 66.5 109.5 25 135 106 1.0 183.4 248.6 103.9 Number of stomachs examined 49 141 120 0.8 49 141 120 O.g 61 141 120 1.1 3 146 139 0.3 14 153 164 1.0 28 141 130 0.9 9 131 97 0.7 25 139 115 1.4 7 153 162 1.1 13 146 144 1.7 22 140 Average weight (lbs.) 127 Average volume of food per pound of body weight (cc.). 0.8 FOOD OF BIGEYE AND YELLOWFIN TUNA 79 Table 9. — Distribution of the volume of stomarh contents of /,S9 yelloivjin and 166 bigeye caught by longline fishing in the central Pacific Less than 140 cm long 140 cm. or larger Volume (cc.) Number Percent of total number Accumu- lated per- centage Number Percent of toUl number Accumu- lated per- centage Empty; (0-0.9): 6 2 17 * 21 9 46 10 49 11 31 13 15 12 4 2 3.2 3.2 9.0 6.3 11.2 14.3 24.0 15.8 26.1 17.5 16.5 20.6 8.0 19 2.1 3.2 0.0 0.0 3.2 3.2 12.2 9.S 23.4 23.8 47.4 39.6 73.5 57.1 90.0 77.7 98.0 96.7 100.0 100.0 4 6 17 10 22 9 50 13 66 1.6 5.8 6.7 9.7 8.7 9.4 19.9 12.6 9fi f Bigeve _ 5 8 1.0-9.9: Yellowfln 8 3 Bigeye 15 5 10.0-24.9: Yellowfin 17 Bigeve _ 24 9 25.0-19.9: YelloHfln... 36 1 Bigeve _ 37 5 50.0-99.9: Yellowfin A3 1 18 17 .1 100.0-199.9: Yellowfin... 56 24 30 17 3 5 3 1 22.2 23.3 11.9 16.5 1.2 4.9 1.2 1.0 85 3 78 3 200.0^99.9: Bigeve 94 8 500.0-999.9 Bigeve 99 7 Yellowfln 100 Bigeye 10(1 Total: Yellowfin 188 63 251 103 T.\BLE 10. — Summary of data relating average volume of stomach contents to condition of fish, whether dead or alive, at time of landing Yellowfin Bigeye Cruise Average volume of stomach contents Number of stomachs examined Average fork length Average volume of stomach contents Number of stomachs examined Average fork length Hugh M. Smitl> cruise 11: Landed dead cc. 93.7 50.6 96.6 71.4 64 23 37 32 cm. 135 141 143 144 cc. 174.9 83.6 11 24 cm. 152 Landed alive John H. Manning cruise 14: Landed dead . Landed alive Jotin R. Manning cruise 15: Landed dead 100.9 280.5 9 10 119 Landed alive 13" SUMMARY AND CONCLUSIONS 1. This study is based on the quantitative analysis of the stomacii contents of 166 bigeye tuna {Parathunnus sibi) and of 439 yellowfiii tuna {Neothunnus macropterus) caught at tlie same time or nearly the same time as the bigeye. 2. These tuna were captured in the central Pacific during the period October 1950-Juiic 1953 by means of longline-gear fishing at deptlis of 150 to 500 feet. 3. The food of the yellowfin consisted of fish (62 percent by volume), squid (29 percent), other moilusks (7 percent), and crustaceans (1 percent); the food of bigeye consisted of fish (62 percent), squid (33 percent), other moilusks (3 percent), and crustaceans (2 percent). 4. Both species of tuna apj)ear to utilize a great variety of animal food, ranging from small plank- ton organisms to large squid and fish. Food items of major importance to both spt^cies were pomfret {Collybus drachme), snake mackerel (Gempylus ser- pens), and squid of the families Ommastrephidae and Loliginidae. 5. This great diversity of diet suggests that many forms of fish, squid, and shrimp — if available through culture or capture might be eflTective as live i)ait or longline bait in tuna fishing. 80 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 6. Stomatopod crustaceans, common in the food of yellowfin, were completely lacking from the bigeye stomachs. The young of other tunas, mostly skipjack, formed a much more important part of the yellowfin diet than of the bigeye diet. 7. In both species, the larger tuna had more food in their stomachs than did the smaller fish, but the larger fish contained less food per pound of body weight than did the smaller fish. There were few completely empty stomachs. 8. In both tunas, the smaller individuals con- sumed a greater proportion by volume of crusta- ceans and fish and a lesser proportion of mollusks than the larger size group. The same fish families were prominent in the diet of botli size groups. 9. There was an increase in volume of stomach contents with depth of capture for the yellowfin; in the bigeye, the largest volumes were found in specimens from intermediate depths. There was no marked variation in composition of stomach contents over the range of depth sampled (esti- mated at 150 to 500 feet), which may be evidence that both the forage organisms and the tuna range rather freely tlnougliout this water layer. 10. In both yellowfin and bigeye, fish were con- sumed in greatest amount during the period April- July, and in least amount during August and Sep- tember. There was little correspondence between the two species in the seasonal variation in the other major food items. 11. In respect to longitudinal variations in the food, the two species were similar in the lower volume of total fish in the stomach contents of those tunas captured in the central region (140°- 150° W. longitude) of the sampled area. The utilization of specific foods did not vary with longitude in any regular pattern for the two species. 12. When classified according to natural subdi- visions of the equatorial current system, the volume of stomach contents in the bigeye varied directly witli the longline catch rate, while in tlie yellowfin there was little change in volume of stomach con- tents with even a marked change in catch rate. 13. Tuna ttiat were dead when landed con- tained, on the average, more food in their stom- achs than those landed alive. 14. Despite the difl'erences that we have pointed out, tlie foods of the yellowfin and bigeye are re- markably similar. We conchuh', tlierefore, that when occupying the same general area the two species have essentially the same feeding habits. If there is any marked food selection, it must be exercised b\' seeking different areas for feeding. LITERATURE CITED BERfi, L. S. 1947. Classification of fishes both recent and fossil. J. VV. Edwards, Ann Arbor, Mich. 517 pp. Brock, V. E. 1949. A preliminary report on Parathunnus sibi in Hawaiian waters and a key to the tunas and tuna- like fishes of Hawaii. Pacific Science, vol. 3, No. 3, pp. 271-277. Cromwell, Townsenu 1951. Mid-Pacific oceanography, January through March 1950. U. S. Fish and Wildlife Service, Spec. Sci. Rept. — Fisheries No. 54. 77 pp. 1953. Circulation in a meridional plane in the central equatorial Pacific. Journal of Marine Research, vol. 12, No. 2, pp. 196-213. Kanagawa Prefectire Fisheries Experiment Station 1951. Report of South Seas tuna fishery investigations. 162 pp. (Partial tran.slation from the Japanese by W. G. Van Campen in the files of Pacific Oceanic Fishery Investigations.) King, J. E. 1954. Variations in zooplankton abundance in the cen- tral equatorial Pacific, 1950-52. Fifth Meeting, Indo- Pacific Fisheries Council, Symposium on marine and fresh-water plankton in the Indo- Pacific, pp. 10-17. KiNfj, J. E., AND Joan Demond 1953. Zooplankton abundance in the central Pacific. U. S. Fish and Wildlife Service, Fishery Bull. 54, vol. 82, pp. 111-144. MlRPHY, G. I., AND R. S. ShOMURA 1953a. Longline fishing for deep-swimming tunas in the central Pacific, 1950-51. U. S. Fish and Wildlife Service, Spec. Sci. Rept. — Fisheries No. 98. 47 pp. 1953b. Longline fishing for deep-swimming tunas in the central Pacific, January-June. 1952. U. S. Fish and VV'ildlife Service, Spec. Sci. Rept. — Fisheries No. 108, 32 pp. 1955. Longline fishing for deep-swimming tunas in the central Pacific, August-November 1952. U. S. Fish and Wildlife Service, Spec. Sci. Rept. — Fisheries No. 137. 42 pp. Nakamira, Hiroshi 1949. The tunas and their fisheries. Tokyo: Takeuchi Shobo. Tran.slated from the Japanese by W. G. Van Campen, U. S. Fish and Wildlife Service, Spec. Sci. Rept.— Fisheries No. 82, 1952. 115 pp. NisKA, E. L. 1953. Construction details of tuna longline gear used by Pacific Oceanic Fishery Investigations. U. S. Fish and Wildlife Service, Commercial Fisheries Review, vol. 15, No. 6, pp. 1-6. FOOD OF BIGEYE AND YELLOWFIN TUNA 81 Orsr, Tamio I')54. Analysis of the Hawaiian longline. fishery, 1948-52. U. S. Fish and Wildlife Service, Commer- cial Fisheries Review, vol. 10, Xo. 9, pp. 1-17. RKIST.IKS, .J. \V., and J. E. KiN Number Percent Cubic centi- meters Percent ' Vert e brat a— Continued 3 13 1 5 2 27 4 1 1 6 1 4 1 13 3 1 0.2 1.4 0.2 0.9 0.2 3.0 0.7 0.2 3.4 10.7 7.0 321.3 31.5 295.3 6.6 1.9 1 7 1 0.6 3.6 0.5 12.0 Hemirhamphidao (halfbeaks) Exocoetidae (flying fishes): 0.7 Par^erocoetus sp_ 0.7 6 1 5 1 3.0 0.6 64.8 1.0 0.3 Bregmacerotidae: Lophotidae (oarfishes) 1 2 1 1 1 1 1 1 0.6 0.6 0.6 0.6 2.8 40.0 190.0 3.9 Trachypteridae (ribbon fishes): TrachypteTus sp 0.2 Regalecidae (oarfishes): 0.9 10 1 5 3 1 2 0.7 0.2 0.5 45.0 94.0 21.6 0.1 0.2 Diretmidae Caulolepidae: A. COTTiUtUS 9 1 2 1 1.2 0.6 2i.6 6.4 27 2 3 1 0.7 0.2 94.0 0.2 0.2 Holoeentridae (squirrel fishes): 1 1 0.6 0.1 Zeidae (John Dories): 2 2 0.5 5.3 Caproidae; Antigonia sp .1. capros , . ._ 11 150 1 1 0.6 0.6 33.0 55.4 0.1 Athcrinidae (sityt'rsides) ; • a 0.2 Polynemidae (fhreadflns) / 1 2 1 0.2 0.2 7.2 29.6 Priacanthidae (ciitalufas): Prica7}thiis cnieiitatus 1 1 0.6 6.8 Apngonidae (cardinal fishes): y^ Pnrascombrops peUucida -^ r 1 7 8 1 2 2 0.2 0.5 0.5 0,6 6,9 4,6 Scorn bropidae: 4 1 1 1 1 1 0.6 0.6 0.6 9.2 1.9 1.2 Sco mbrops sp Unidentified Scombropidae Carangidae (jacks): 1 1 1 1 0.2 0.2 88,0 118,0 0.2 0.3 1 1 0.6 8.6 1 1 1.012 88 2 244 2 3 2 1 8 1 1 190 33 1 1 66 2 1 2 1 1 0.2 0.2 43.3 7.5 0.2 0.2 15.0 0.5 0.2 0.5 0.2 0.2 115,7 1.8 3. 465. 9 786.3 3.0 4,2 675,2 118.1 1.4 3.3 1.5 21.0 0.3 Unidentified Carangidae Bramidae (pomfrets): CoUyhus drachme 7.8 1.8 76 34 26 22 15.7 13.3 2. 550. 8 835.5 11.4 3.7 P ocellatus 1 18 1 10 0.6 6.0 14.8 476.9 1.5 0.3 2.1 Coryphaenidae (dolphins): Unidentified Coryphaenidae 3 2 1.2 2.6 Leiognathidae MuUidae (goat fishes): 1 1 0.2 1.2 1 i 0.6 3.7 Chat'todontidae (butterfly fishes) 5 3 26 12 n 31 1 202 1 10 7 3 2 10 3 1 10 1 80 1 I 1 0.7 0.5 2.3 0.7 0.2 9.2 1,8.1 0,2 0.2 0.2 29.3 4.4 39.5 24.8 12.8 97.9 21.9 2.119.5 0.4 21.5 36 r I 1 7 1 1 3 0.6 0.6 1.8 7.6 2.0 29.9 Chanipsodontidae' Ckampsodon sp Chiasmodontidac 0.1 Acanthurida'' (sureeon fisjics): . \ 0.2 Geiiipylidae (snake mackerels): 4.7 86 2 1 43 i 25.9 0.6 0.6 2. 023. 7 2.4 4 A 9.1 1 2 18 48 1 1 18 0.6 0.6 0.6 10.8 5.5 2.8 80.0 .■(76 :< Rexea solandrii _ " i' 149 i 62 0.'? 14.1 i.8' 7X6.2 OA UnidimtificMl (Jcmpylidae i.8 1.7 See footnote at end of table. FOOD OF BIGEYE AND YELLOWFIN TUNA 85 Table II.— Check-list of food organisms found in the stomachs of 439 yellowfin and 166 bigeye tuna captured on longline in the Central Pacific, 19S0-.53— Continued {Family names of fishes are as given in Berg 1947) Yellowfin Bigeye Food organisms Number of organ- isms Stomach.'! in which occurred Aggregate total volume Number of organ- isms Stomachs in which occurred Aggregate total volume Number Percent Cubic centi- meters Percent ' Number Percent Cubic centi- meters Percent • Vertebrala— Continued Sconibridju- (mackerels); Scomber sp ♦-— -•- 9 4 41 14 2 41 2 3 16 4 1 12 0.5 0.7 3.6 9 0.2 2.7 21.4 68.6 102.3 30.8 10.0 79.0 0.3 0.2 Nonn'ida<' (rudder fishes): •. 34 8 6 3 3.6 1.8 76.9 22.8 3 Cuhiceps sp ---■ 1 C. tfinmpsoJti _.. __ 0.2 4 1 15 3 2 1 10 1 1.2 0.6 6.0 0.6 10.4 5.6 75.0 17.5 .\Ioitodactytv3 sp. _ 58 2S 5.7 122.6 0.3 3 Thunnldae (tuna fishes): .Sardi^p --- 48 2 1 68 1 6 16 4 4 12 26 8 23 fi 1 8 11 33 78 3 18 11 ) 9 3 ) ^ ' 3 13 19 17 2 1 12 1 4 8 2 3 11 20 5 12 3 1 7 7 14 29 3 13 10 6 2 2 7 1 5 1 10 12 3.9 0.5 0.2 2.7 0.2 0.9 1.8 0.5 0.7 2.5 4.6 1.1 2.7 0.7 0.5 1.6 1.6 3.2 6.6 0.7 3.0 2.3 1.4 0.5 0.5 1.6 0.2 1.1 0.2 2.3 2.7 3,497.1 962.0 32.2 1,961.0 70.0 12.2 144.8 26.0 14.3 145.8 116.3 72.6 412.5 134.0 6.8 71.9 27.8 78.3 322.7 15.3 243.4 27.1 77.0 57.5 215.7 lis. 1 10.0 66.1 54.0 162.3 4,318.8 7.8 2.2 Seothunnu^ macropttruit 1 1 0.6 662.0 3 Germn aialunijn 4.4 0.2 2 2 1.2 224.0 1 rnidenllflod Thunnldae 1 1 0.6 1.0 E'^heneidae (renioras): 0.3 Rfmara sp 0.3 0.3 0.2 0.9 0.3 Unidentified Echeneidae. 7 3 i.8 S.6 Balistidae (trigger fishes): Balistes sp. li. iiycteris li. riuQens . Xanthkhfbijs sp_.. I'nidentified Balistidae ._ 0.2 Monacanthidae (file fishes).-. .. . Ostraciidae (trunk fishes); Ostrncioti sp 0.2 0.7 15 8 1 2 1 2 2 1 2 1 1.2 1.2 0.6 1.2 0.6 23.0 29.7 2.5 69.5 0.6 1 Lactoria s\) 0.5 3 Unidentified O.straciidae 0.2 0.1 0.5 0.3 Lagocephalus sp L...^... ? Telrodon sp . / I'nidentified Tetrodontidae. 1 1 0.6 16.6 Diodontidae (porcupine fishes); C.ailinis >. / 0.1 0.1 0.4 9.7 Unidentified Diodontidae / 1 2 1 1 2 0.6 0.6 1.6 0.1 113 Molidae (sun fishes); Ranzajtja SI) . . . .... n (I Unidentified Molidae 151 n " Antennariidae (frogfishes): 1 1,160 1 213 0.2 48.5 0.8 2.968.9 44, 679. 5 439 Other and unidentified fish 6.6 511 81 48.8 3. 884. 22, 297. 3 166 17.4 Total food Number of stomachs examined ' Given only when 0.1 percent or greater. U. S. GOVERNMENT PRINTING OFFICE 1956 O— 388734 UNITED STATES DEPAETMENT OF THE INTERIOR FISH AND WILDLIFE SERVICE CORRECTIONS for Fishery Biilletin 108, COMPARATIVE STUDY OF FOOD OF BIGEYE AND YELLOWFIN TUNA IN THE CENTRAL PACIFIC Page 62, second coliimn, line 10: for "latitudes" insert "longitudes." Pages 69 and 73: Figures 9 and 10 are transposed (the captions are correctly numbered). Page "JB, table 8: Under Atherinidae, for " Atherinus insularum" insert "Pranesus insularum ." Page Qk, table 11: Under Exocoetidae, for " Paraexocoetus " insert " Parexocoetus ." Under Atherinldae, for "A. insularum" insert " Pranesus insularum ." Under Acanthuridae, f or "''^epatus sp." insert " Acanthurus sp." Under Gempylidae, for " Neoephinnula " insert " Neoepinnula . " Page 85, table 11: Under Thimnidae, for "Sardi" insert "Sarda." Under Tetrodontidae for " Sphoeroides lagocephalus" insert " Lagocephalus lagocephalus . " Under Diodontidae, for " Cheilomycteris " insert " Cheilomycterus ." 11067 P f LIFE HISTORY OF LAKE HERRING OF GREEN BAY, LAKE MICHIGAN By Stanford H. Smith, Fishery Research Biologist The lake herring, or shallowwater cisco, Leu- cichthys artedi (LeSueur) , occurs in all of the Great Lakes and in many inland lakes of the St. Law- rence, Hudson River, and upper Mississippi River drainages (Hubbs and Lagler, 1949), and has rather general distribution throughout Canada and Alaska in lakes and some rivers, and in Hudson and James Bays (Dymond 1933, 1943, and 1947). Close relatives of the lake herring have a circumpolar distribution in the glaciated areas of the Northern Hemisphere. The lake herring is a member of the family Coregonidae, a complex and not well understood group of fish. Much confusion resulted from early attempts to describe tliis group in the Great Lakes (see Koelz 1929; pp. 311-314). The dis- agreement stemmed botli from the fact that early workers studied only small numbers of specimens from one or a few localities and from the high degree of individual and geographic variability in size, shape, and taxonomic counts that charac- terizes this group. Koelz made a comprehensive ta.xonomic study of coregonids inhabiting the Great Lakes and Lake Nipigon based on about 15,000 specimens from many parts of each lake. He recognized the high degree of variabihty in the group and was able to organize the confused taxonomy. What had been described as several species by comparisons of a few specimens often were found to be representatives of a single species that varied greatly in form over its range. Koelz recognized the different species inhabiting the several lakes and thus established a system of nomenclature which has since been adequate for the species of the Great Lakes. He recognized all coregonids of the Great Lakes as belonging to the family Coregonidae and the genera Coregonus (Artedi) Linnaeus, Leucichthys Dybowski, and Prosopium Mihier that had been described from studies of coregonids over their entire range. A few authors have deviated recently from the system of classification used by Koelz and have placed Leucichthys and Prosopium in the genus Coregonus. I prefer to retain Leucichthys as a genus because it represents a well-defined group in North America. The Leucichthys group in Europe is ascribed to the subgenus Aryyrosomus; however, European workers have written me that these fish are distinct from other coregonids of that continent. The consolidation of all groups under the single genus Coregonus disregards the recognizable divergence of the phyletic lines represented by the three genera. It is true that the high degree of morphological plasticity characteristic of the coregonids sometimes causes morphometric and even gross appearances to approximate or, in isolated instances, to overlap each other. This superficial parallelism may occasionally hide the distinctness of the groups, but it cannot overrule the primary genetic divergence that is so clearly shown by the distributional pattern of each group. For each genus there is a central range where its members are highly variable {Coregonus in Europe, Prosopium in northwestern North America, Leuci- chthys in northeastern North America), and where they are usually divided into several spe«?s7" Range extensions of each group are characterized by lesser morphological variability and at the extremes only one or two relatively stable species remain. Ambient morphological divergences in isolated populations of one group may in some instances parallel developments common among members of another group and thereby tend to obscure the distinctness of the groups. Such occurrences cannot, however, be interpreted as incomplete separation of the groups. 1 believe the separate genera describe these phyletic lines in the clearest and most useful manner and shoidd be retained in keeping with this basic purpose of modern taxonomy. 87 88 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE Because of its varied form in different localities, the lake herring is known by more than one com- mon name. Names used in this work where other authors are quoted are sometimes cisco or tullibee rather than lake herring. These names are most often applied to the deep-bodied forms that occur in inland lakes and Lakes Erie and Ontario. Most lake herring from the upper Great Lakes, however, are of the characteristically shallow-bodied form that is most commonly termed "lake herring." The lake herring is of major importance in the commercial fishery of Green Bay. Fluctuations in its abundance bring a degree of economic uncer- tainty to the people who depend upon this fish for part of their livelihood. Although the lake herring has been important in the commercial catch of Green Bay, little has been known about it. Knowledge of this species provides greater under- standing of its reactions to changing environ- mental conditions, and also is required to develop management principles that would allow maximum utilization of the species without depleting the population. A study of the life history of the Green Bay lake herring was initiated in 1948 when field collec- tions of scales were made by Dr. Ralph Hile, of the United States Fish and Wildlife Service, as part of a cooperative project with the Wisconsin Conservation Department for the study of Green Bay fish populations. After 1950, field work was carried on by the author with the help of Leonard S. Joeris and Donald Mraz of the Sturgeon Bay field station of the Service's Great Lakes Fishery Investigations. During 1952, the research vessel FWS Cisco, operated by the Great Lakes Fishery Investigations, was available for approximately 1 week each in May, July, and October for the study of the distribution of lake herring in Green Bay. Some material on the lake herring of Green Bay was collected during parts of two other cruises of the Cisco in May and June. The author is most grateful to Drs. Ralph Hile, John Van Oosten, and James W. Moffett, U. S. Fish and Wildlife Service, and to Dr. Karl F. Lagler, University of Michigan, for valuable guidance during the conduct of the study. GENERAL FEATURES OF GREEN BAY Green Bay is a nearly detached arm of Lake Michigan with its long axis roughly parallel to the northeast shore of the lake. Morphometric features of Green Bay and Lake Michigan are compared in table 1 . The two bodies of water are similar in that they are long and narrow, but they differ greatly in depth and area. The greatest length of Green Bay is about 118 miles on a northeast-southwest axis between the upper end of Big Bay de Noc and the city of Green Bay, Wis. (fig. 1). The greatest width, about 23 miles, is on a northwest-southeast axis in the region of the northern island passages. The area of Green Bay included within a line drawn between the town of Fairport and the tip of the Door Peninsula near Gills Rock is approximately 1,590 square miles. The greatest depth, about 160 feet, is just northwest of Washington Island. The bay is relatively shallow — mean depth, 51 feet. One- third of its area is less than 30 feet deep and only 1 1 percent is more than 100 feet deep. Table I. — Morphometric features of Lake Michigan and Green Bay [Data from the U, S, Lake Survey Chart Nos. 7 and 70, 1953 edition] Measurement Greatest length (miles) . Greatest width (miles). Shoreline length (miles) Area (squarf miles) Volume (cubic miles) __ Greatest depth (feet)... Mean depth (feet) LakeMich- igan 307 ng 1,661 22.400 1,165 932 274 Green Bay 118 23 379 1,590 15 160 51 Four major channels in the northern island area with depths of 45 to 130 feet connect Green Bay with Lake Michigan. The manmadc Sturgeon Bay Canal which is 160 feet wide and 20 feet deep joins the two bodies of water in the southern area at Sturgeon Bay. A study being carried on by the Great Lakes Fishery Investigations of the United States Fish and Wildlife Service has pro- vided some data about the exchange of water between Green Bay and Lake Michigan. Al- though not as comprehensive as might be desired, the data do give a general idea of the water -ex- change system between the lake and bay, and of water movements within the bay. An outstanding feature of the water movements in Green Bay is tlie high degree of irregularity in direction and velocity. The direction and rate of water movements are believed to be governed . mainly by wind and barometric pressure. Flow of water into the bay from rivers is believed to be of minor importance in the major water move- ments except during spring runoff. Movement LAKE HERRING OF GREEN BAY, LAKE MICHIGAN 89 Figure 1. — Map of Green Bay showing locations of experimental gill-net -stations. Triangles, shallow-water stations (A, 30 feet; B, 40 feet); squares, 60-foot stations; circles, 90-foot stations. 90 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE of Lake Michigan water into Green Bay is charac- terized more by surges than by a regular movement. Surges into the bay result primarily from seiche action set in motion by wind and pressure changes over Lake Michigan. The resultant currents in tlie bay cause a tremendous amount of mixing. In the northern passages the sequence of inflow, mixing, and outflow result in a great amount of water excliange between the bay and the lake. Evidence of a high degree of exchange in the northern area is found in the relatively clear. Lake Michigan-type water that lacks the deep green color produced by dense phytoplankton growth characteristic of the remainder of the bay. Def- inite lines of demarcation cannot be made on this basis, however, because of mixing of water masses. Clear lake water is sometimes observed in the Sturgeon Bay area, but here a sharp line of demar- cation is usually present between the two types of water. This condition indicates that little mixing occui-s before the lake water is returned with an outgoing surge through the canal. In addition to water movements propagated by currents and water-level changes in Lake Michi- gan, the water in the bay itself is subject to indig- enous seiches and currents caused by local condi- tions. The systems operating simultaneously in lake and bay, as they must most of the time, result in extremely complex and irregular water move- ments. The water level in Green Bay is subject to almost continuous chaiige. A change of a foot an hour is not uncommon and occasionally a drop of several feet in the southern end of the bay strands fishing boats in shallow harbors. Although a complex resonance pattern is characteristic of water-level charts of Green Bay, peaks occur at intervals of about 12 hours. The peaks show no relation to the movements of the moon. Typical spacing of the peaks within the 24-hour period can be completely disrupted by severe storms after which a new system is established with peaks occurring at different hours of the day but again at 12-hour intervals. Some of the effects of water movements on the water temperatures in Green Bay will be shown later in a discussion of the distribution of lake lierring. ECONOMIC IMPORTANCE OF THE FISHERY Green Bay supports one of the most productive commercial fisheries of the Great Lakes and the lake herring is a major contributor to the catch. Hile, Lunger, and Buettner (1953) showed that on the average 28.8 percent of the total pounds of all species taken in the State of Michigan waters of Green Bay consisted of herring. In 1952, the last year for which complete statistics and values are available, the lake herring catch of Green Bay (both Wisconsin and Michigan) amounted to 9,121,600 pounds and had a value to the fishermen of $456,080. This catch represented 94.1 percent of the production of this species in all of Lake Michigan and 38.7 percent of the lake herring production of all United States waters of the Great Lakes. The commercial production of the lake herring in Green Bay is characterized by wide annual and seasonal fluctuations. The catch in Michigan waters of Green Bay ranged from 1,515,000 to 11,850,000 pounds (average 5,841,000 pounds) from 1891 to 1908 (Hile, Lunger, and Buettner, 1953) and averaged 82.4 percent of the total pounds of all species taken. In a later period (1929-49) there was a marked drop in the produc- tion to between 160,000 and 2,668,000 pounds (average 1,070,000 pounds) which contributed an average of 29.9 percent to the catch of all species. The production of lake herring in Michigan and Wisconsin waters during the years for which reliable records are available for both States (table 2) show wide variation seasonally and annually. Fluctuations of the catch are influ- enced primarily by weather, availability and abundance of other species with higher market value, and the abundance of lake herring itself. Thus, the causes of fluctuations are difficult to ascertain, but the great difference between the 1891-1908 and 1929-49 data on the Michigan waters of Green Bay (82-percent drop in average production) shown by Hile, Lunger, and Buettner indicates that the population must be subject to wide variations. The present study, however, has been conducted in years (1948-52) when total production has been high and relatively stable LAKE HERRING OF GREEN BAY, LAKE MICHIGAN 91 (6,320,000 to 9,122,000 pounds) compared to the 10-year period after 1936. Table 2. — Commercial catch of lake herring in Wisconsin and Michigan waters of Green Bay, by quarters, 1936-53 [In thousands of pounds] Year January- March April- June July-Sep- tember October- December Total 1936 1,121 1,475 1,422 381 653 382 299 330 249 581 854 1,686 2,260 1,354 1,788 1,322 1,818 587 897 1,127 779 513 399 347 249 428 292 791 1,381 1,223 1,576 1,622 1,065 593 675 842 254 246 142 158 146 129 119 303 333 1,003 687 338 303 376 747 563 384 1, 597 1,254 665 449 291 442 182 223 131 1,289 2,294 1,832 3,288 3,041 3,663 5,049 6,066 4,081 3,869 1937 4, 102 1938 3,008 1939 1,.')01 1940 1,489 1941 1,300 1942 849 1943 1944 .. .. 1,284 1,005 1945 3,664 1946 5 216 1947 5,285 1948 7,462 1949 6,320 1950 1951 6,892 7,711 1952 9,122 19.'J3 . 5,894 Average, 1936-53 Percentage... 1,031 24.4 822 19.5 376 8.9 1,991 47.2 4,220 Note. — These data are from summaries of commeicial catch records made by the V. S. Fish and Wildlife Service for Michigan waters and by the Wisconsin Conservation Department. Data for Wisconsin prior to 1942 included lake herring taken in that area of Lake Michigan adjacent to Green Bay, but catches in this area arc characteristically small and are not believed to influence trends. Because of highly seasonal production and rapid deterioration in handling and storage, the lake herring brings a low average price (5 cents per pound to the fishermen of Green Bay in 1952) and much of the catch is used for animal food. Given better markets and improved handling, the species may become a more important source of human food. The lake herring has some small value as a sport fish. Its habit of feeding principally on small planktonic organisms and its disinclination to strike at lures has caused it to be overlooked by anglers using conventional methods. During recent years, however, fishermen have found that when lake herring are feeding on mayflies tliej' will also strike at artificial flies. A sports fishery during the period of mayfly emergence is growing rapidly in popularity in the northern areas of Lakes Huron and Michigan. Some large lake herring are also taken with minnows as bait. A certain amount of angling for lake herring is carried on through the ice botli on the Great Lakes and on inland lakes. COLLECTION OF DATA Scale samples and data on weight, length, sex, and state of development of se.x organs w'erc ob- tained on 4,390 specimens. Collections made between May 26, 1948, and January 22, 1952, w^ere taken from commeicial pound nets and gill nets as indicated in table 3. Scale samples of May, July, and October, 1952, were from fish captured in experimental gill nets. Table 4 lists all fish taken in experimental gill nets for whi(rh length and weight measurements and sex determi- nations were made; in some of the May collec- tions, however, weight and sex data are missing. Table 3. — Collections of Green Bay lake herring from which scale samples were taken, 1948-5S Date Locality Gear used ' Num- ber of nsh IH8 Mav26. Point Comfort .-. Schumachers Point... Schumachers Point... Point Comfort 262 Oct. 12... 238-inch gill net 152 19(9 Feb. 16 345 May 13 . do 200 13 Pensaukee do 241 Oct. 5 do do 283 19S0 Feb, 22 Schumachers Point do 341 27 .. do-— 166 June 21 Fish Creek do 62 22. do. do 25 July 13 ... do 43 Sept. 14 OUls Rock do 201 Nov. 29.... Fo.x do 107 30 2?8-inch gill net 108 Dec. 4 Sister Bay.. 112 1951 Feb. 20 2?8-inch gill net 168 20.-.- do 29 20 Ingallston. . do 223 22 .- Schumachers Point... Point Comfort do 189 May 8. do 143 June 152 0111s Rock .. do 11 19 do 80 21... Gills Rock Fox Gills Rock do do do 26 Aug. 20 59 29 15 Nov. 11 Pensaukee 2^2-inch giU net 80 Dec. 12 Gills Rock 79 I9SI Jan. 21 Escanaba Pound net 90 22 Pensaukee.. Station D . do 92 Mav 8 2-lnch gill net 44 11 113 Julv 21 Station L Station C do do 30 24 19 Oct. 22 23 . Station B Station I^ do do 46 19 24 Station I do 187 Total 4,390 ' See text, p. 95, for comment* on mesh sizes of pound nets. » This is a selected sample. All other samples are either random or repre- sent the entire catch of one net. 388748 O — 57- 92 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE Table 4. — Lake herring taken in experimental gill nets in 1952 Date' Sta- tion! Num- ber of flsh Date Sta- tion! Num- ber of flsh May 2. D I D E F O E F G A B C J K L J K 80 28 58 26 115 118 85 31 31 13 32 5 81 19 46 78 51 July 21 L H I C D A B C D H I J K L 85 ^ 6 22 22 10 8 24 11 24 19 11 27 6 11 Oct. 22 15 22 22 22 46 22 143 22 23 19 25 24 140 25 24.. 25 26 25 Total ... 25 Tnnp n 179 130 12 12 139 July 21 2,039 21 ' Weight and sex data lacking for some May collections. 2 See figure 1 for location. Total length (tip of the snout to the end of the tail, lobes compressed) was recorded to the nearest 0.1 inch. Weights measured on a spring scale, with 18-ounce capacity, were recorded to the nearest 0.1 ounce. All lengths are given in inches and weights in ounces unless otherwise stated. Samples from the commercial fishery were cap- tured in standard fishing gear designed primarily for lake herring. Netting of pound nets used in the lake herring (and smelt, Osmerus mordax) fishery customarily has meshes (in the pot) of 1)4 to 2 inches, extension measure as manufactured. Nets of these mesh sizes are capable of capturing lake herring smaller than any taken from them during this study. Consequently, mesh size need not be considered as a selective factor in the treat- ment of samples from pound nets. Most small- mesh gill nets used in the Green Bay herring fishery have a mesh size of 2% inches (allowable range 2)^ to 2% inches, depending on season, loca- tion, and conditions) extension measure. One col- lection in southern Green Bay was taken from a 2)Mnch-mesh gUl net on November 11, 1951. Experimental gill nets used to collect lake herring in the summer and fall of 1952 are described in Vertical Distribution in Green Bay (p. 128). All experimental gill nets were fished from the Service's research vessel Cisco. Analyses and discussions in this report include all data that are believed pertinent to the solution of each particular problem. The exclusion of data of doubtful value in some instances causes dis- crepancies in the number of specimens listed in diff'erent tables. Whenever the excluded data are extensive or may influence results under alter- nate considerations, the reason for their omission is given. All collections of data used in this report are either taken from the entire catch of a net or are random samples unless otherwise stated. EXAMINATION OF SCALES Scales for age and growth analysis were taken when possible from the left side of the body in the area just above the lateral line and below the in- sertion of the dorsal fin. Van Oosten (1929, p. 274) stated that this area was selected "* * * after a careful examination had shown that its scales were less variable in shape and size, when compared one with another, than those of other parts of the body." Since the scales of lake herring are loosely attached and are frequently lost in nature, a liberal sample was taken to ensure the inclusion of non- regenerated scales. The scales from each fish were placed in an envelope on which were recorded the species, locality, date, length, weight, sex, condi- tion of sex organs, gear, and name of collector. The "key" scales required to establish the body- scale relation were removed from approximately the center of the area from which routine samples were taken. The location was the same as that used by Van Oosten — the fourth row above the lateral line and immediately below the base of the first ray of the dorsal fin. Some scales were mounted on glass slides in a glycerin-gelatin medium. Plastic impressions were made of the others. Each slide carried three or four scales of normal shape and without evi- dence of regeneration. The label on the slide bore the data shown on the envelope from which the scales were taken. Plastic impressions of scales were made by placing six or eight dry, uncleaned scales sculptured side down on a 1- by 3-inch strip of cellulose acetate bearing a serial number corresponding to that on the scale envelope. A second plastic strip was placed over the scales and the two strips were passed through a roller press set at the crushing pressure of cellulose acetate. (See Smith 1954.) The sec- ond strip of plastic holds the scales in position and ensures an even impression which produces a light, clear image. The numbered plastic strips bearing scale impressions were returned to the envelope and thus were not separated from the original data. LAKE HERRING OF GREEN BAY, LAKE MICHIGAN 93 Before the plastic-impression method was adopted, careful microscopic comparisons were made of the scales and their impressions to be certain that replication was complete and without distortion. Butler and Smith (1953) who studied the reliability of scale impressions in age and growth studies found that growth calculations made from scale impressions did not differ signif- icantly from those made from the scales them- selves. About 500 of the scales used in this study were mounted in a glycerin-gelatin medium ; plastic impressions were made of the remaining 3,900. AH key scales used to establish the body- scale relation were mounted in glycerin-gelatin. Scale measurements for growth computations were made from the magnified (X41) scale image projected on the screen of a microprojection de- vice (described by Moffett 1952) and recorded to the nearest millimeter. The scale to be meas- ured was oriented so that a line on the viewing "screen bisected the image at its greatest antero- posterior diameter. Measurements of the total diameter and of diameters of growth fields cir- cumscribed by annuli were made along this line. The total diameter was measured from the extreme anterior to the extreme posterior margins of the scale. Diameters of growth fields were measured from the inside edge of the first complete circulus outside the annulus. Scale measurements of each fish were entered on IBM (International Business Machine) cards along with coded information concerning each fish. All subsequent computations and tabula- tions were made by means of the 602A IBM calculator and the 404 IBM tabulator at the Statistical Research Laboratory of the University of Michigan. Ages were determined by counting the annuli or year-marks on the scales. Van Oosten (1929) clearly established the validity of this method for the age determination of the lake herring of Saginaw Bay. More recent authors reporting on this species (Carlander 1945; Cooper 1937; Fry 1937; Hile 1931, 1936; Pritchard 1931 ; Stone 1938; and others) have accepted the use of scale mark- uigs for age analysis of lake herring. Nothing in the data on the Green Bay lake herring gives cause to question the validity of scales for age determination. Nevertheless, cer- tain difficulties of interpretation were encountered. Accessory checks, or false annuli, occurred on scales of nearly all fish after the second year of life. The general appearance of these checks and their location with respect to the annuli on either side left little doubt as to their identity; however, the possibility of some errors of age determination cannot be discounted. The regular appearance of accessory checks is not confined to the Green Bay stock. These false annuli on cisco scales have been reported by HUe (1936) in the cisco of Muskellunge Lake and by Fry (1937) in Lake Nipissing. Bauch (1949) described a fast-slow-fast growth pattern in a population of "kleinen Marane," Coregonus albula L. (the European coregonid most similar to the lake herring), in Mochelsee. He attributed the midseason check in the scales to oxygen depletion and an accumulation of hydrogen sulfide in the hypolimnion which forced these fish, nor- mally inhabitants of the deeper waters in summer, to live in upper strata where less favorable tem- perature conditions exist. Data on the Green Bay herring are inadequate to show the cause of accessory checks or even the time of their forma- tion. Seemingly the formation of checks varies from fish to fish and possibly' according to season and locality. The characteristics of the annulus on the scales of Green Bay lake herring are similar to those described for scales in other populations. The circular ridges on the scale start forming on the anterior margin of the scale and grow posteriorly along the lateral fields. When growth stops com- pletely and resumes again, growth of the un- finished circuli is not completed; instead a new circulus is started which encompasses the ends of those left incomplete at the cessation of growth. Fish having scales without an annulus are designated as belonging to age group 0, those with one annulus to age group I, * * *. For convenience, each fish is held to pass into the next higher age group on January 1. Since annulus formation does not actually take place until spring or early summer, the convention requires that a "virtual" annulus be credited at the edge of the scale from January 1 until the new annulus is visible. Year classes are identified by year of hatching (spring) rather than year of egg deposi- tion (fall). Thus, it is always possible to de termine the year class of a fish by subtracting its age from the year of capture; for example, a fish 94 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE Table 5. — Age composition of lake herring taken in commercial pound nets, by quarters, 1949-52 [Dominant age groups indicated by asterisk] Quarter and year Number offish Percentage in age group— I II III IV V VI VII age 1 January-March: 1949 345 505 437 178 12.2 10.9 7.1 3.9 •74.2 •74.8 •80. 1 •87.1 13.6 13.5 12.6 8.4 4 01 1950 . 0.8 4.05 1951 0.2 4.05 1952 0.6 4.06 All years, 1949-52 1,465 0.1 9.2 •77.8 12.6 0.3 4.04 April-June: 1948 262 439 87 246 1.5 •53.6 16.2 10.3 16.7 42.2 •73.3 •72.4 •67.5 2.7 9.1 14.9 ID. 1 3.46 1949 1.4 2.4 0.4 3.96 1950 4.09 1961 4.9 0.4 3.86 All years, 1948-51 1,034 1.5 25.3 •64.0 8.2 0.9 0.1 3.82 July-September: 1950 244 73 2.9 8.2 2.9 30.1 ♦50.8 27.4 40.5 •32.9 2.9 1.4 3.38 1951 - - - - 2.89 All years, 1960-51 317 4.1 9.2 •45.4 38.8 2.5 3.06 October-December; 1949 278 219 0.7 0.5 6.8 5.9 •76.3 •68.9 15.1 24.7 0.7 0.4 3.09 1950 3.18 All years, 1949-50 497 0.6 6.5 •73.0 19.3 0.4 0.2 3 13 ' Average number of annull. belonging to age group III captured in 1949 be- longs to the 1946 year class. AGE COMPOSITION The principal characteristics of the age com- position of Green Bay lake herring taken in the commercial fishery (tables 5 and 6, and fig. 2) are the shift from older to younger fish during the calendar year and a strong tendency for the same age group to be dominant year after year during the same season. In pound-net collections made during the first quarter (January-March), age group IV was Table 6. — Age composition of lake herring taken in com- mercial gill nets, in 1948. 1950, and 1951, and experi- mental gill nets in 1952, by quarters [Dominant age groups Indicated by asterisic] Quarter and year Num- ber of flsh Percentage in age group— Aver- age I II III IV V VI age 1 166 154 48 3.0 3.2 35.4 •80.1 •85.1 •64.6 16.9 11.1 6.6' 4.14 April-June: 1952 4.09 July-September: 1952. . 3.65 October- December: 1948 152 108 80 250 'i.9" 3.9 4.6 2.5 0.4 •52.6 •72.2 •85.0 •60.8 38.2 19.4 10.0 37.2 6.3 1.9 2.5 1.6 3 45 1950 3. 15 1951 3 13 1952 3 40 All years, 1948-52.... 590 0.3 2.4 •64.1 30.5 2.7 3.33 100 80 60 40 20 I 60 I 20 uj 80 O < P 60 z uj O 40 X UJ °- 20 60 60 40 20 APRIL - JUNE JULY - SEPTEMBER IV V AGE GROUP ' Average number of annuli. Figure 2. — Age composition of lake herring taken in com- mercial pound nets (solid line), and commercial and experimental gill nets (broken line) in various quarters, 1948-52. LAKE HERRING OF GREEN BAY, LAKE MICHIGAN 95 without exception strongly represented (74.2 to 87.1 percent) and made up 77.8 percent of all fish taken over the period 1949-52. In April-June collections the IV-group was still strongest in 3 years (67.5 to 73.3 percent) and made up 42.2 percent of the sample in the remaining year. The percentage of IV-group fish dropped from 77.8 in the first quarter to 64.0 in the second, whereas the Ill-group increased from 9.2 to 25.3 percent. Age group III was dominant in the summer quar- ter (July-September) in one of the two samples (50.8 percent) as well as in combined data of 1950-51 (45.4 percent). The transition to domi- nance by age group III was complete in the fourth quarter (October-December) , where it maintained this position in both years (68.9 and 76.3 percent) and in combined data for 1949-50 (73.0 percent). The dominance of the Ill-group (73.0 percent), which advances to age group IV on January 1, is only slightly less than that of the IV-group of the first quarter of the following year (77.8 percent). The mid-year shift of dominance from age group IV to age group III is also shown clearly by the average ages (table 5). The much less extensive data on gill-net sam- ples ' (table 6 and fig. 2) suggest that the trend of age composition is much the same as for pound nets. Age group IV was dominant, but the average age was decreasing in the first three quarters and age group III was dominant in all samples of the fourth quarter. Despite similar trends in the seasonal shift of age composition, gill nets in general took older fish than did pound nets. The small differences where large numbers of fish were concerned, how- ever, indicated that during the years of this study both gears were cropping a similar segment of the population. The age composition of the commercial catch demonstrated for Green Bay requires that a differ- ent year class be a major contributor to the fishery each year. The fishery, in turn, must then be very sensitive to fluctuations in success of year classes. Because of the resulting instability in the economy of small fishing communities it would be advantageous to devise some method of predicting good and poor year classes before they enter the fishery so that problems of high or low production ' Collections from experimental and commercial gear are shown together In Elll-net data. Figures presented In a later discussion on length at capture show that lake herring taken In the two types of gears at the same time of year have similar length distributions. could be anticipated. Unfortunately, this study has been conducted during a period of high and relatively stable production (see Economic Impor- tance of the Fishery, p. 90) and no fluctuations or means of their detection were discernible. The catch and abundance (expressed as catch per unit- of-effort), however, are normally subject to wide fluctuations (Hile, Lunger, and Buettner, 1953). The age composition of a representative sample of an entire population should normally show a preponderance of fish in the youngest age group, with progressively decreasing numbers as age increases. This pattern of diminishing numbers with age must exist in lake herring populations (even though it has never been demonstrated), for a population that regularly has fewer young fish than old must soon disappear. Since young lake herring have to be abundant, their scanty repre- sentation in samples of the population must be attributed either to the inability of collecting gear to capture them or to their absence from the area sampled. It is believed that the scarcity of young herring in the 1948-52 samples was largely the result of their scarcity on the fishing grounds. A principal gear of capture, the pound net, was fully capable of taking lake herring as young as 1 or 2 years old had they been present in abundance. Pound nets from which lake herring were taken for this study were also designed to capture smelt. Because of their small size and slender form, smelt require smaller mesh sizes than do the lake herring and yellow perch {Perca flavescens), which constitute important portions of the commercial catch. Mesh sizes ranging from 1 }i to 2 inches, extension measure as manufactured, made even smaller by treatment with preservative, have been used in Green Bay since smelt became an important com- mercial species about 1940 (Hile, Lunger, and Buettner, 1953). Although this mesh was far smaller than was previously considered satisfac- tory to catch commercial-sized herring, its intro- duction did not result in any continuous appear- ance of smaller herring in the catch even though it regularly captured yearling smelt and perch. In southern Green Bay, large numbers of trout- perch (Percopsis omiscomaycus) 3 to 4 inches long are regularly taken. The ability of pound nets to catch young herring was clearly demonstrated in the winter of 1944-45 when, according to Hile, Lunger, and Buettner, 96 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE large numbers of "pin" herring were taken in pound nets. Scales from 78 specimens taken at Escanaba on May 27, 1945, revealed that all were fish of the 1943 year class and were nearing the end of their second year of life. Inasmuch as this has been the only phenomenal occurrence of small herring in smelt-type pound nets since they came into common use, it can be assumed that the appearance in numbers of young herring in 1945 could have resulted from a successful hatch in 1943 and that the abnormally plentiful young herring extended beyond their normal range into the shallow-water areas in which pound nets are located. Although lake herring average about 5 inches long at the end of their first year of life, which is within the size range of other small fish taken, none were ever present in our pound-net samples. The lake herring is a relatively short-lived species. Hile (1936) reported the maximum age of XII in Trout Lake, Wisconsin. Although no other author has reported a fish this old, fish in age group XI have been reported by Fry (1937) in Lake Nipissing and by Hile in Clear Lake. Lake herring in age group X have been reported by Carlander (1945), Eddy and Carlander (1942), Stone (1938), and Van Oosten (1929). The low- est maximum age reached in any population was reported by Hile for Muskellunge Lake where the oldest fish belonged to age group IV. The oldest age groups in these populations are represented in the samples by only one or two individuals; in most lake herring stocks heavy mortality starts between the third and seventh years of life. The oldest lake herring taken in Green Bay were two Vll-group fish caught in pound nets in June 1951.^ Only 17 representatives of age group VI were recorded during the course of this study. The observed age compositions of several North American lake herring populations show that age groups II to V are best represented in the samples and that of these age groups III is usually the most common. Some of the differences among samples from various populations were undoubtedly the result of selectivity of collecting gear. It appears, nevertheless, that fish are much shorter lived in some populations than in others. Hile (1936) collected fish from several lakes with the same gill ' One of the VH-group fish was in a selected sample collected on June 15, 1951, and does not appear In discussions dealing with age. The other VII group flsh wa.s In the June 19, 1951, collection. nets, and his data should be well adapted to a comparison of age composition in different bodies of water. Hile's data show that age groups II and III were best represented in the Muskellunge and Clear Lake populations, but that the oldest fish taken in Muskellunge Lake belonged to age group rV, whereas in Clear Lake ciscoes lived as long as 1 1 years and age group VII made up more than 11 percent of the samples. The difference between these two lakes in observed age composi- tion is as great as that recorded elsewhere in the literature. It is possible that differences reported by other authors can be real and that the longev- ity does vary with local conditions. Van Oosten (1929) showed that age group III (age group IV under his system of age designation) predominated in his samples from Saginaw Bay, all of which were taken from pound nets during the period October to December. This same age group dominated samples taken from Green Bay pound nets during the same time of the year (table 5). SIZE AT CAPTURE The lengths of lake herring captured in pound nets (table 7) and gill nets (table 8), varied both as to average and range among collections of the same year and of different years. Mean lengths for samples, however, show no distinct seasonal pattern, which is in marked disagreement with the well-established, seasonal changes in age composi- tion (see p. 94). The data on age would suggest that the consistently older fish taken during the first half of the year should be longer than the predominantly younger fish taken in the second half. The discrepancy is explained by the length frequencies of age groups (table 9) which show a wide overlap of length distribution where length groups are frequently represented by fish of three ages. Differences between mean lengths of age groups III and V were only 0.4 to 0.7 inch in different years. Thus, lake herring of these age groups are similar in length regardless of age and no great changes in length should be expected to follow changes in age composition. That there is a greater growth than is indicated by the average lengths of age groups is brought out in a later discussion of computed growth. The apparently poor growth suggested by the similar average lengths of different-aged fish in the com- mercial catch must be due either to a strong LAKE HERRING OF GREEN BAY, LAKE MICHIGAN 97 Table 7. — Length distribution of lake herring taken in pound nets, by month and year, 1948-6S Total length May 1948 1949 1950 1951 Jan- uary (Inches Feb. May Oct. Feb. Jane July Sept. Nov. Dec. Feb. May June Aog. 1952 1 1 2 1 2 1 3 6 21 S 6 2 3 7 10 6 2 1 6 .S to 6 fi 1 I 1 3 3 6 10 11 4 2 7 5 to 7 9 1 4 5 7 12 29 82 100 27 10 2 2 1 1 8 to 8 4 1 2 4 10 60 181 146 26 7 1 2 i' 8 47 49 28 6 1 1 2 2 2 3 9 20 27 21 12 3 8 5 to 8 9 1 5 41 98 67 28 18 2 1 1 2 8 36 172 190 81 11 3 2 1 1 1 9 14 35 16 9 2 3 8 16 69 82 24 6 1 1 35 160 95 44 8 2 4 12 103 186 111 19 5 1 9 5 to 9 9 3 21 45 32 3 1 2 3 12 64 29 3 1 4 100 to 10.4 8 10.5 to 10.9 -- 5« 11.0 to 11.4 73 11 5 to 11 9 34 12 to 12 4 4 12 5 to 12 9 2 13 to 13 4 1 i 1 14 5 to 14 g 1 1 1 1 1 Number of flsh 262 10.5 34S 10.5 441 10.7 283 10.8 S07 10.6 87 10.8 43 9.5 201 10.9 107 10.8 112 10.8 441 10.8 143 11.2 106 10.7 74 9.3 182 11.1 Table 8. — Length distribution of lake herring taken in gill nets^ by month and year^ 194S-5S 1 Collections from 2^i-tnch-mesh commercial gill nets. ' Collections from 2>2-inch-mesh commercial gill nets. ' Collections from 2-inch-mesh experimental gill nets. Total length (Inches) October 1948 > November 1950' 1951 1952 • Feb.i Nov.« May July Oct. 7.5to7.9 1 1 1 8 to 8 4 8.5 to 8 9 1 9.0to9.4 1 1 9.5 to 9.9.. _ 2 12 44 87 15 6 2 4 26 63 46 13 3 1 5 16 17 5 6 10.0 to 10 4 4 18 33 55 23 14 3 4 21 33 26 14 5 1 1 9 10.5 to 10.9 5 20 28 16 9 1 1 64 11.0 to 11.4.- _ 104 11.5 to 11.9 58 12.0 to 12.4 5 12 5 to 12 9 13.0 to 13.4 1 13.5 to 13.9 14 to 14 4 1 Number offish 152 11.7 108 11.3 168 11.1 80 11.7 157 10.9 49 10.6 252 11.2 Table 9. — Length distribution of lake herring, by age group, taken from pound nets in January and February, 1949-SS Total length 1949 1950 1951 1952 (inches) III IV V III IV V VI II III IV V HI IV V VI 8.0 to 8 4 1 8.5 to 8.9 2 3 9 19 17 6 1 1 1 3 10 45 152 115 18 6 9.0 to 9.4 1 24 123 71 32 3 2 2" 14 16 5 27 138 143 59 5 1 i 4 6 48 65 28 3 1 9.5 to 9 9 9 23 8 2 10.0 to 10.4 .. 15 29 16 5 1 2 11 13 4 1 4 14 25 7 1 1 2 1 2 2 3 1 4 5 4 1 10.5 to 10.9 ll.fl to 11.4 11.5 to 11.9 12.0 to 12.4 12.5 to 12.9 1 13.0 to 13.4 14.0 to 14 4 14.5 to 14.9 Number of fish Average length 42 10.3 256 10.4 47 10.7 66 10.3 378 10.5 68 10.9 13.0 1 8.1 31 10.5 350 10.8 55 11.2 7 10.8 155 11.1 15 11.2 1 12.6 98 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE modification of the population by the fishery (that is, a selective destruction of the larger fish) or to a differential distribution of the fish according to size so that only a certain segment of the popula- tion is represented in the fishery. Since the second condition obviously would contribute to the first, it may be assumed that the commercial fishery exerts a strong modifying effect on the population. Natural mortality, of course, may also play an important but unmeasurable role in this process. A progressive increase in length of lake herring of each age group in successive years from 1949 to 1952 (table 9) indicates that more rapid growth took place in the later years. This trend is also brought out in a later section on annual fluctua- tions in growth rate. Small as variations were in the average lengths of lake herring collected at different times of the year (tables 7 and 8), November-May collections taken at about the same time but often at con- siderable distances apart, showed still smaller differences of no more than 0.2 inch. This similarity was not always present, however, for in collections of other months (June-October) large differences sometimes occurred. Examples of these small differences in average lengths of herring taken in different areas are given in the following table: Date Location Average length (Inches) May 13... Suamlco 10 8 13 Pensaukee 10 7 Feb. 11... lUO Schumachers Point 10 6 27 10.5 Nov. 29 Fox 10 8 Dec. 4 Feb. 20.-. 1961 Ingallston 10 7 20- Pensaukee Schumachers Point Escanaba 22 - 10 9 Jan. 21... 196B 22 The weight.of Green Bay lake herring at capture presents much the same picture as does length. Weights of fish of a given age are distributed over a wide range and each weight group is frequently represented by fish of three ages (table 10). Differences between age groups III and V varied only 0.6 ounce to 1.2 ounces in different years as would be expected when differences in length were small. GROWTH BODY-SCALE RELATION AND CALCULATION OF GROWTH Van Oosten (1929) established the validity of computations of the growth of lake herring from the diameters of the entire scale and of growth fields within the several annuli. Since the publi- cation of his work, most investigators reporting on growth of this species have accepted Van Oosten's conclusions. The relation between body length and the anterior scale radius of lake herring was determined for the tullibee of Lake of the Woods by Carlander (1945). Carlander used the anterior radius be- cause he found annuli difficult to locate in the posterior field. He demonstrated that the rela- tion between scale radius and standard length was described satisfactorily by a third-degree equation. From a comparison of results of calculations from diameters and anterior radii Van Oosten (1929, p. 327) found that "* * * the diameter of a scale grows in length more nearly proportional with the body than does the anterior radius [and] * * * that the diameter dimension is less variable than the anterior radius * * *." Since no difficulty was experienced in locating annuli in the posterior field of scales of Green Bay lake herring, diameter measurements were used in this study to take advantage of the simple, direct-proportional rela- tionship determined by Van Oosten. It was held desirable, nevertheless, to study the body-scale relation of the Green Bay lake herring to make certain that the procedure was valid in this stock. If direct-proportion computations are to be valid, the body-scale ratio must be the same for all lengths of fish from the time of completion of the first annulus. Van Oosten (1929) found that after formation of this annulus the ratio of total scale diameter to body length was so nearly constant in the herring of Saginaw Bay that an assumption of constancy could be made. In the Green Bay lake herring the body-scale ratio exhibited no trend with increase in fish length (table 11). A f-test to determine whether such variations as did occur represented a significant trend confirmed the validity of the assumption that the ratio does not change with length (0.8 Males - - 11.0 11. 1 1952: 1 Males - 10. s 10.6 I Collected from 2-inch-mesh experimental gill nets. ' Collected from 2H-inch and 2>4-inch-mesh commercial gill nets. Effect of gear selection on estimation of growth From a review of tlie literature and from his own data Hile (1936, pp. 298, 306) held that— * * * in general a sparse representation in a sample of a young age group whose average length is near the lower limit of effectiveness of the nets used, is a source of suspicion as to the reliability of the sample of that particular group. If this same sparsely represented group gives calculated growths that are in serious disagreement with those of the older age groups it should be eliminated from the data used for the study of growth in the population as a whole. 104 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE Hile concluded that — * * * if these selected groups are eliminated the re- maining growth data can be considered accurate and trustworthy within very narrow limits. If Hile's assumptions are correct we should find close agreement between growth of best-repre- sented age groups of herring talten in gill nets and herring of the same ages taken in the less-selective pound nets. This expectation is fulfilled by the data of table 17. Growth of the best represented age groups (III, IV, and V) was almost identical in pound-net and gill-net samples. In shorter age groups, I and II, the greater calculated lengths of herring from gill-net samples indicate that the larger, faster-growing individuals are selected by gill nets. This tendency for herring caught in gill nets to be larger than those taken in pound nets is still present though somewhat reduced in age group III. Because the effects of gill-net selection extends to ages as high as the Ill-group (which is frequently dominant), most detailed analyses of growth in later sections have been based on pound- net samples alone. Table 17. — Comparison of growth of lake herring taken in pound nets and in gill nets, by age groups [Calculated total length in inches] Net' Num- ber of fish Length at end of year of life— 1 2 3 4 5 6 Age group I: 16 2 78 16 906 404 2,018 475 208 69 11 1 6.1 6.2 5.2 5.8 6.4 6.6 5.3 5.2 5.0 4.9 5.0 5.3 Gill Age group H: 8.1 9.0 81 8.2 7.8 7.8 7.4 7.3 7.8 7.1 Gill Age group III: 9.9 10.0 9.6 9.5 8 9 9.0 9.7 8 6 Gill Age group IV: 10.6 10.7 10.1 10.2 11.0 10.2 Gill Age group V: Pound - 11. 11.2 12.1 11.3 Gill Age group VI: 13.1 Gill 12.0 ' Collections from pound nets in 1948-52, and from 2 to 2)4-inch-mesh experimental and commercial gill nets in 1948 and 1950-52. Seasonal differences The apparently slow growth indicated by small differences between lengths of lake herring of different age groups at capture, brought out in a previous discussion of the length frequencies of age groups, again suggests the possibility of se- lective destruction of fish of more rapid growth by the commercial fishery. If such a selective destruction is taking place and is strong, it should result in growth differences detectable in samples taken in the same year but several months apart. That selective destruction was sufficiently great to influence estimates of growth is indicated by the data of table 18. In every comparison, except the third year of life, in the Ill-group taken in 1949, fish caught earlier in the year had higher calculated lengths than did those taken later. In 14 of 18 comparisons the advantage of the early- season over the late-season fish amounted to 0.4 inch or more. Because of the seasonal differences in growth patterns in fish of the same age group it is necessary to stratify samples according to sea- sons when making discriminating comparisons. Table 18. — Comparison of growth of lake herring, by age group, taken in pound nets at different seasons, 1949-51 [Calculated total length in inches) Location and date of capture Num- ber of flsb Length at cap- ture Length at end of year of life— 1 2 3 4 SooTHEKN Green Bay Age group III: Feb. 16, 1949. 42 212 256 42 23 73 133 31 172 23 10.3 10.8 10.4 U.2 10.2 10.7 10.5 11.0 10.7 11.1 6.0 6.2 5.5 4.8 5.5 5.3 5.0 4.9 5.2 4.8 8.6 7.9 7.9 7.4 8.4 7.8 7.7 7.3 7.7 7.3 10.3 10.3 9.4 9.0 10.2 9.7 9.3 8 9 9.4 9.0 Oct. 5, 1949 Age group IV: Feb. 16,1949 Oct. 6, 1949 - 10.4 10.3 NoKTHERN Green Bay Age group III: Feb. 27, 1950 - Nov 29 1950 Age group IV: Feb. 27, 1950 --- 10.6 Nov 29, 1950 10.1 Feb. 20, 1951 10.7 Aug. 20, 1951 10.3 Geographic differences That environmental conditions must differ in the various parts of Green Bay is obvious (see General Features of Green Bay, p. 88) . If environ- mental conditions influence growth and if the pop- ulation is not regularly mixed by active migration or passive transport with currents, differences in the growth of lake herring captured in various sections of Green Bay should be detectable. Differences between growth in northern and southern waters of the bay are indicated by com- parisons of lake herring taken in pound nets at the same time of year at locations separated by considerable distances (table 19). In 10 compari- sons of size at capture for fish of the same age, northern fish were shorter in six, and longer in two; lengths of the remaining two groups were LAKE HERRING OF GREEN BAY, LAKE MICHIGAN 105 Table 19. — Comparison of growth of lake herring, by age groups, taken in pound nets at the same time of year at different locations [Calculated total length In inches] Date and locality Area Number offish Length at capture Length at end of year of lite— Length increment 1 2 3 4 5 1 2 3 4 S Feb. 22-27, 1950: Age group III: North 23 33 245 133 9 59 73 78 31 23 6 22 172 154 41 12 79 76 8 7 10.2 10.3 10.5 10.5 11.5 10.8 10.7 10.8 11.0 10.9 10.0 10.7 10.7 10.9 11.1 11.5 11.1 11.1 11.0 11.5 5.5 5.9 5.0 5.4 4.8 5.0 5.3 5.5 4.9 6.2 5.3 5.8 5.2 5.4 4.8 5.0 5.0 5.5 4.5 5.1 8.4 8.6 7.5 7.9 7.4 7.2 7.8 7.9 7.3 7.5 7.9 8.7 7.7 7.9 7.2 7.5 7.7 8.0 6.9 7.7 10.2 10.3 9.3 9.5 9.1 8.7 9.7 9.7 8.9 9.0 10.0 10.7 9.6 9.7 8.8 9.0 9.7 9.8 8.6 9.3 5.5 5.9 5.0 S.4 4.8 6.0 6.3 5.5 4.9 5.2 5.3 6.8 5.2 5.4 4.8 5.0 6.0 6.6 4.5 5.1 2.9 2.7 2.5 2.5 2.6 2.2 2.5 2.4 2.4 2.3 2.6 2.9 2.5 2.5 2.4 2.6 2.7 2.5 2.4 2.6 1.8 1.7 1.8 1.6 1.7 1.5 1.9 1.8 1.6 1.5 2.1 2.0 1.9 1.8 1.6 1.5 2.0 1.8 1.7 1.6 South Age group IV: North 10.5 10.5 10.5 9.9 11.5 10.8 1.2 1.0 1.4 1.2 South Age group V. North 1.0 Schumachers Point South 0.9 Nov. 29-Dec. 4, 1950: Age group III: North Sister Bav South Age group IV; North 10.1 10.1 1.2 1.1 South Feb. 20-22, 1951: Age group III: North South Age group IV: North 10.7 10.9 10.1 10.4 11.1 11.1 9.8 10.6 11.1 11.5 11.0 11.5 1.1 1.2 1.3 1.4 1.4 1.3 1.2 1.3 Schumachers Point South Age group V: Ingallston North 1.0 South 1.1 Jan. 21-22, 1952: Age group III: North.. - Pensaukee South Age group IV: Escanaba North 1.2 Pensaukee South 0.9 equal in the two areas. Differences between growth of lake herring from northern and southern localities are much more apparent in the calcu- lated lengths. Without exception northern fish grew less in their first year than did southern fish. Although growth increments of the northern fish were predominantly larger than those of southern fish in the second year and were without exception greater in the third year, the initial handicap of slower growth in the first year was overcome by the end of the third j^ear of life in only 2 of 10 pairs of samples. By the end of the fourth year, however, the initial differences in size in the two areas had largely disappeared. The significance of this comparison may be questionable in the light of information brought out in a later discussion (Growth Compensation, p. 109), that fish with poor first-year growth also tend to be slightly shorter at capture than fish having better growth in the first year. It is possible then that differences between calculated lengths of lake herring in northern and southern samples may be a reflection of differences in the length at capture. That such an explanation is not adequate is indicated, however, in the data of table 20 which gives comparisons of the growth histories of fish of the same age in the same }^-inch length interval. Northern Green Bay fish of the same length and age as the southern Green Bay fish at capture tended to be shorter than the southern at the ends of their first, second, and third years of life; but after the first growing season northern fish usually grew more than southern fish. This similarity of growth differences in selected length intervals and entire age groups is evidence that northern and southern fish do have different patterns of growth. The hypothesis of a north-south gradient is suggested by the fact that differences in first year's growth are greater in samples taken farther apart. Annual fluctuations in growth rate Since calculated growth histories of lake herring in Green Bay differ according to season and geo- graphical location, studies of annual fluctuations in growth must be based on samples taken in the same location at the same time each j'ear. The series of samples that best met these require- ments were taken in the southern part of Green Bay in January or February in the years 1949 to 1952. The materials for the study of annual fluctuations in the growth based on these coUec- 106 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE Table 20. — Comparison of growth of lake herring, of same age and length at capture, taken in pound nets at the same time of year at different locations [Calculated total length In inches] Length group and locality Number offish Length at capture Length at end of year of life- Length Increment Feb. 22-27, 1950; Age group IV; 10.&-10.4 in.: Escanaba (north) . _ _ Schumachers Point (souths Age group IV; 10.5-10.9 in.: Escanaba (north) Schumachers Point (south). Age group IV; 11.0-11.4 In.: Escanaba (north) Schumachers Point (south). Nov. 29-Dec. 4, 1950: Age group III; 10.0-10.4 In.: Fox (north) Sister Bay (south) Age group III; 10.5-10.9 in.: Fox (north) Sister Bay (south) Age group III; 11.0-11.4 In.: Fox (north)-- --. Sister Bay (south) Feb. 20-22, 1951; Age group IV; 10.0-10.4 In.: Ingallston (north) Schumachers Point (south). Age group IV; 10.5-10.9 in.: Ingallston (north) Schumachers Point (south). Age group IV; 11.0-11.4 in.: Ingallston (north) Schumachers Point (south). Jan. 21-22, 1952: Age group IV; 10.5-10.9 in.: Escanaba (north) Pensaukee (south) Age group IV; 11.0-11.4 in.: Escanaba (north) Pensaulcee (soutli) Age group IV; 11.5-11.9 In.; Escanaba (north) Pensaukee (soutli) 37 106 10.2 10.3 10.7 10.7 11.3 11.2 10.3 10.3 10.7 10.7 11.1 11.1 10.3 10.2 10.7 10.7 11.1 11.1 10.7 10.8 11.2 11.1 11.7 11.6 5.0 5.2 5.0 5.5 5.1 5.6 6.1 4.9 5.4 5.5 5.2 5.6 5.1 5.2 5.1 5.4 5.4 5.4 4.8 5.3 5.1 6.6 5.2 6.8 7.3 7.6 7.6 8.0 7.9 8.3 7.5 7.3 7.9 7.9 7.9 8.1 7.4 7.5 7.7 7.8 8.0 8.0 7.6 7.7 7.8 8.2 8.3 8.4 9.0 9.2 9.4 9.9 10.0 9.3 9.3 9.7 9.0 9.0 9.4 9.5 9.8 9.8 9.4 9.6 9.8 10.2 10.3 10.2 10.3 10.7 10.7 11.3 11.2 10.3 10.2 10.7 10.7 11.1 11.1 10.7 10.8 11.2 11.1 11.7 11.6 5.0 5.2 6.0 6.5 6.1 6.6 5.1 4.9 5.4 6.6 6.2 5.6 5.1 6.2 5.1 5.4 5.4 5.4 4.8 6.3 5.1 5.6 5.2 5.8 2.3 2.4 2.6 2.5 2.8 2.7 2.4 2.4 2.5 2.4 2.7 2.6 2.3 2.3 2.6 2.4 2.6 2.6 2.7 2.4 2.7 2.6 2.1 2.6 1.7 1.6 1.2 1.1 1.3 1.1 1.4 1.2 1.9 1.9 1.3 1.2 1.3 1.2 1.3 1.3 1.3 1.2 1.4 1.2 1.5 1.3 tions (table 21) are so arranged that in each section of the table the vertical columns show the calculated growth in different years of life but in the same calendar year, the horizontal rows give a comparison of the growth in different calendar years for the same year of life, and each diagonal row gives the growth history of a single year class. For the quantitative determination of annual fluctuations of growth the data were subjected to the analysis described by Hile (1941), a procedure involving the determination of the percentage change in growth from each year to the next. The chain of estimates thus obtained was then ad- justed to a mean of 0.0 for the period of years cov- ered by the data (table 22). The fluctuations show a trend toward an improvement of growth during the period covered and show a possible tendency to be cyclic. From a value slightly below average in 1944 ( — 2.1 percent), growth declined to a minimum of —6.5 in 1946 (fig. 5). The year 1947 was the first in a 4-year period of improvement that culminated in growth 9.1 per- cent above average in 1950. Figure 5. — Fluctuation of growth in length of lake herring from the 1944-51 mean. Temperature is commonly considered an im- portant factor in the determination of fluctuations in growth. Hile (1936, pp. 276-280) discussed the possible influence of air temperature on the growth ofcisco populations in northeastern Wis- consin lakes and cited works of several authors who found a positive correlation between summer temperatures and the amount of growth of sev- eral European species of coregonids. Concerning the Wisconsin cisco populations Hile concluded — The failure of variations in the amount of growth in different calendar years to show any close general depend- LAKE HERRING OF GREEN BAY, LAKE MICHIGAN 107 ence on either annual variations in temperature or annual variations in population density suggests that possibly these variations in growth depend closely on both factors, and that the failure of these factors fo operate in the same direction in the same year tends to obscure the effect of each of them. Van Oosten (1929) found no correlation between annual fluctuations in first-year growth and annual fluctuations in the air. temperatures during the growing season for Saginaw Bay lake herring. More recently, Svardson (1951) has shown that the growth of whitefish in Sweden was greater in hot summers than in cool. The data for the Green Bay lake herring (table 22) give no evidence of a definite relation between fluctuations of growth and deviations of mean air temperatures or population density over the 8-year period 1944 to 1951. Table 21. — Annual calculated growth increments of lake herring from pound nets in southern Green Bay in January or February, 1949-52 .\gc group and year Annual growth increment (inches) in— of life 1944 1945 1946 1947 1948 1949 1950 1951 Age group IH: 1.7 2.7 5.8 1.0 1.6 2.5 5.5 0.8 1.2 1.5 2.6 1.7 2.9 6.0 1.0 1.8 2.5 2.0 2.9 2.0 2.6 5.9 6.0 Age group IV: 4th vcar 1.2 1.8 1.3 1.5 2.5 5.4 2.4 5.4 5.5 Age group V: 51 h year 0.9 1.4 1.6 1.1 1.3 0.9 i.i 1.5 2.5 5.1 1.3 2.2 5.0 2.4 5.0 5.1 Number of flsh in age group: III 42 245 12 33 154 7 22 76 6 IV 256 59 V 47 Table 22. — Deviation of growth, air temperature during the growing season (May-October), and abundance of lake herring in southern Green Bay, from the average for the 8-year period, 1944-51 Year Percentage growth devi- ation Mean tem- perature de- viation " F. ' Abundance = 1M4 -2.1 -4.1 -6.5 -3.8 -2.1 3.1 9.1 6.7 2.0 -1.8 -0.1 1.4 0.8 1.8 -2.1 -2,0 -63 IW.V _ ^ H»4ti . . ._ -36 24 1947 24 1948 28 1949 ...: 14 \\IH\ 5 Wb\ . . 4 ' Mean monthly deviations of air temperatures for the period May-October recorded by t^ S. Weather Bureau at Green Bay, Wisconsin. 2 Percentage deviation fioni average catch per unil-iif-efTort in pound and gill net.s computed from Wisconsin commercial catch records for southern Green Hay (Wisconsin commercial fishing district M-1). Discrepancies in calculated growth The systematic discrepancies among calculated growth histories of different age groups already noted for the Green Bay lake herring are a frequent, almost regular, characteristic of data on growth of fish. These differences occur among different age groups of the same year class as well as among age groups of different year classes. The pattern of the discrepancies varies from species to species and stock to stock. Most common is that which goes under the name of Lee's phenomenon of "apparent decrease of growth," in which the esti- mates of lengtii at the end of various years of life decrease with increase in the age of the fish on which the estimate is based. In this "typical" situation, tlie calculated lengths in the earlier years of life show the greatest disagreements. More recent authors have tended to depart from this definition and to apply the term "I^ee's phenom- enon" to all systematic discrepancies among calculated lengths. The literature on causes of Lee's phenomenon, in both the restricted and the broader sense, is extensive and to a considerable degree contro- versial. A review of the subject at this time could serve little purpose.' It may be useful, never- theless, to list the principal factors that liave been offered in explanation of systematic discrepancies in calculated lengths. These several factors, the significance of which will become clearer from later discussions, are as follows: 1. Use of wrong formula for growth calcula- tions. 2. Selective action of fishing gear. 3. Biological segregation on basis of size or maturity. 4. Higher mortality rate (natural or in the fishery) of the fish with the more rapid growth. In the consideration of discrepancies among calculated lengths of Green Bay lake herring, the first of these items is not significant since the validity of the method of calculation was estab- lished by a study of the body-scale relationship. The effects of gear selectivity (item 2) can be rendered insignificant by confining studies of growth discrepancies to samples taken by pound nets, which, as has been pointed out, were capable of capturing fish smaller than the smallest herring « See Van Oosten (1929) and lllle (1936) for detailed discussions of the prob- lem. 388748 O — 57- 108 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE Table 23. — Calculated total length of lake herring at the end of each year of life, by age group and year class, 1943-50 [Pound-net samples only. Length in inches] Age group Num- ber of flsh Length at end of year of lite— of capture 1 2 3 4 5 6 7 1950 year class: I I II III I II III IV II III IV V II III IV V VI III IV V VI IV V VI VII V VI 6 8 35 2 20 119 155 19 340 661 15 4 326 594 83 1 141 619 88 1 110 89 6 1 7 3 4.3 5.7 4.4 5.9 6.2 5.8 5.4 6.3 5.8 6.4 6.2 4.8 5.9 6.6 5.2 4.9 4.8 5.9 6.4 4.9 6.1 5.1 5.1 6.0 5.0 6.2 4.8 1949 year class: 1950 1951 7.3 8.7 1952 10.8 1948 year class; 1950 8.6 8.0 7.9 8.9 8.0 7.7 7.2 9.7 8.1 7.7 7.4 7.8 8.2 7.9 7.3 9.7 7.7 7.4 7.9 8.3 8.0 7.5 1951 9.9 9.7 11.1 1947 year class: 1949 1950 9.8 9.6 8.9 1951 10.8 10.2 1952 11.2 1946 year class: 1948 1949 9.9 9.3 9.0 9.6 10.2 9.5 8.8 11.9 9.6 8.8 9.7 10.0 9.6 8.9 1050 10.5 10.3 10.8 1951 11.3 11.9 1952 12.6 1945 year class: 1948 1949 10.6 10.0 13.3 10.6 9.9 11.1 U.3 10.6 10.1 1960 10.9 14.8 1951... 16.3 1944 year class: 194S 1949 10.9 12.3 12.6 11.5 11.0 1950 1951 1943 year class: 1948 13.3 13.6 14.6 1949 12.0 appearing in the samples. Such discrepancies as do appear, therefore, are to be attributed princi- pally to factors 3 and 4. The inconsistencies among the calculated growth histories of the different age groups of the several year classes ' of the Green Bay lake herring (table 23) differ from Lee's phenomenon as originally described (Lee 1920). It is true that the estimates of length for a particular year of life did tend to decrease with increase in age of fish on which estimates were based. On the other hand, the size of the differences did not decrease with increase in the number of years of life as is charac- teristic of Lee's phenomenon. In all but one comparison between age groups represented by 15 or more fish the estimate of first-year length decreased with increase of age (the one exception is in age groups IV and V of the 1944 year class). The trends were similar for the second-, third-, and fourth-year calculated lengths, but exceptions were more numerous. ' The most discriminating comparisons are those among different age groups of the same year class, since these are not biased by annual fluctua- tions in growth. It is believed that the discrepancies among the calculated lengths of the age groups of the Green Bay lake herring represent the combined effects of segregation according to size within the popula- tion and of selective destruction of the faster- growing individuals in the fishery made possible by that segregation: . Because of the connection between these two factors it is difficult to judge their relative importance. - In fact, an attempt to separate the two is not desirable, since they are essentially parts of a single process. In the younger age groups, only the largest fish (a small percentage of the total) enter the pound- net fishery. (Note the small representation of age groups I and II in collections — table 17). Se- lection in the gill-net fishery is similar (table 17), but the effects of selective destruction probably occur later in gill nets than in pound nets. This biological selection (plus gear selection in gill nets) leads to the overestimation of the rate of growth in those age groups. At the same time, destruc- tion of the larger, fast-growing fish modifies the growth characteristics exhibited by the remaining stock. As members of a year class grow older, bias to the immediate sample resulting from the selective capture of the larger fish declines, but the cumulative effects of destruction of the faster-growing individuals become increasingly important. Ten populations of Leucichthys artedi, for which various authors have given figures of calculated growth of different age groups, have all exhibited Lee's phenomenon to some degree. Disagree- ments were large in only one of four cisco popula- tions in northeast Wisconsin (Hile 1936). In the Irondequoit Bay cisco population the growth rate decreased with increased age among the younger age groups, but differences were random at the higher ages (Stone 1938). Fry (1937) found only small discrepancies among the estimates of the first-year growth of the Lake Nipissing cisco, but disagreements were large in later years. The variation in the nature of the discrepancies in calculated growth of fish of different age in the several populations leads to the conclusion that the causes of Lee's phenomenon are not the same in all populations. Principal explanations of the phenomenon in lake herring advanced by various authors are — 1 . Selective action of gill nets used in collecting samples. LAKE HERRING OF GREEN BAY, LAKE MICHIGAN 109 2. Segregation as to maturity during the spawning run. 3. Segregation as to size, independent of ma- turity. 4. Higher mortality rate among fast-growing fish than among slow-growing. Hile (1936) found that discrepancies in the calculated lengths of ciscoes in three of four Wisconsin lakes were the result of faulty sampling traceable to selective action of gill nets. Carlander (1945) attributed Lee's phenomenon in ciscoes of Lake of the Woods, Minnesota, to the selectivity of large-mesh gill nets, as well as to differential mortality of fast- and slow-growing fish as pro- posed by Hile (1936). Eddy and Carlander (1942) also found the phenomenon in ciscoes of Gull Lake, Minnesota. Van Oosten (1929) and Cooper (1937), whose samples came from spawning-run lake herring in Saginaw Bay and Blind Lake, respectively, offered similar explanations of Lee's phenomenon. Their views are expressed adequately in the following quotation (p. 570) from Cooper's paper: * * * the lake herring first reaches maturity during its third, fourth, or fifth year of life, depending upon individual rate of growth; the more rapidly growing individuals of any one year class attain maturity first. It follows that the youngest year groups were represented in the catch (from the spawning grounds) only by their biggest indi- viduals and, as older age groups were considered, more and more of those fish that had been smaller individuals in their earlier years appeared in the older groups. There- fore the younger age groups contained a larger proportion of fast-growing fish than did the older groups and, con- sequently, the computed lengths for the early years of life would be greater in the younger age groups than in the older. The persistence of the phenomenon in the older age groups (in groups in which all individuals are mature) may be explained on the basis of differential mortality, that is, on the assumption that the more rapidly growing fish die off earlier in life than the more slowly growing fish. In Green Bay, as has been pointed out, segregation by size (^and hence by rate of growth within a year class) appears to take place at all seasons. Evidence was presented by Hile (1936) that a high natural mortality rate was correlated with rapid growth in the cisco population of Silver Lake. Cooper has suggested differential mortality as a possible factor in Lee's phenomenon. Hile also advanced the hypothesis that, if there was scgriigation of fast- and slow-growing fish with depth, the gill nets which were always fished on the bottom could not take equal samples of both. Fry (1937) demonstrated that faster-growing young fish were found in deeper waters of Lake Nipissing during the summer and were joined in successive years by more and more of the slower-growing members of the same year class. Behavior of this type explains why Lee's phe- nomenon might be found in samples taken in a certain location at a particular period of the year. Although a difference in seasonal distribution of fast- and slow-growing lake herring may exist in Green Ba}' and may be contributing to Lee's phenomenon there, it cannot be the main causative agent, because the phenomenon exists in samples collected at different depths and at different locations in the same and different seasons. Growth compensation Growth compensation — the tendency for the smaller fish at a particular age to have the more rapid subsequent growth — seems to be common among fish (V&n Oosten 1929 ; Eddy and Carlander, 1942). The existence of growth compensation was mentioned in 4 of 14 publications on growth of lake herring (Carlander 1945, in Lake of the Woods tullibee; Eddy and Carlander, 1942, in the tullibee of 17 Minnesota lakes; Hile 1936, in the cisco of four Wisconsin lakes; and Van Oosten 1929, in the Saginaw Bay lake herring). Growth compensation seems to be a general occurrence in North American coregonids. It has been shown in the following stocks: Lake Michigan kiyi (Leucichthys kiyi) by Deason and Hile (1947); Reighard's chub (Z. reighaidi), longjaw cisco (Z. alpenae) and bloater (L. hoyi) of Lake Michigan by Jobes (1943, 1949a, and 1949b); Lake Huron whitefish by Van Oosten (1939) ; and Lake Superior longjaw {L. zenithicus) by Van Oosten (1937). McHugh (1941) did not find growth compensation in several populations of Rocky Mountain white- fish (Prosopium vnlliamsoni) . Of the authors who mentioned growth com- pensation in studies of lake herring only Hile (1936) and Van Oosten (1929) discussed its char- acteristics in any detail. Carlander (1945, p. 129) stated that— As was demonstrated for the ciscoes by Van (losten (1929) and Hile (1936), growth compensation occurs in the Lake of the Woods tullibee but the compensation is not great enough to overcome any advantage in length which large individuals may hold at the end of the first year. 110 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE Table 24. — Calculated growth of lake herring grouped by size in different years of life [Based on IV-group fish of Feb. 16, 1949, sample collected at Schumachers Point. Terminal groups contain 15 percent and middle groups 35 percent of total number of fish. Mean lengths for the year of life of grouping and corresponding growth increments are italicized. Maximum difference between lengths in parentheses] Total length (inches) Number offish Length at end of year of life— Length Increment 1 2 3 4 I 1 2 3 4 1st year of life: 3.7to4.9 38 90 90 38 38 90 90 38 38 90 90 38 38 90 90 38 i.e S.l 5.7 e.s (1.6) 5.0 5.3 5.6 6.0 (1.0) 5.0 6.3 5.6 ,5.8 (0.8) S.2 5.4 5.6 5.7 (0.5) 7.4 7.7 8.1 8.5 (1.1) 7.1 7.7 8.1 s.e (1.5) 7.2 7.7 8.1 8.4 (1.2) 7.4 7.8 8.0 8.3 (0.9) 9.1 9.3 9.5 9.8 (0.7) 8.9 9.3 9.6 9.9 (1.0) «.8 9.g 9.6 W.l (1.3) 8.9 9.2 9.5 10.0 (1.1) 10.3 10.3 10.5 10.8 (0.5) 10.1 10.4 10.5 10.9 (0.8) 10.0 10.2 10.5 11.1 (1.1) 9.9 10.1 10.6 11. S (1.3) i.6 6.1 5.7 2.8 2.5 2.4 2.3 1.7 1.6 1.4 1.3 1.2 4 9 to 5 5 . 1.0 1.0 6.0 to 6.7... - --- 1.0 2d year of life: 6.0 to 7.4 -- 5.0 5.3 5.6 6.0 I. I s.i 1.6 i.6 1.8 1.6 1.4 1.3 1.2 7 4 to 7 9 .-- __- - 1.1 79to84. 0.9 8 4 to 9 4 1.0 3d year of life: 5.0 5.3 6.6 5.8 2.2 2.4 2.5 2.6 1.6 l.B l.B 1.7 1.2 9 to 9 4 . . . 1.0 94to9.9 - 0.9 9.9 to 10.9 -- - 1.0 4th year of life: 9 3 to 10 5.2 5.4 5.6 5.7 2.2 2.4 2.4 2.6 1.5 1.4 1.5 1.7 1.0 10 to 10.4 1.0 10 4 to 10.9 1.1 10 9 to 12 1 - - l.t 1 Length at capture. The characteristics of growth compensation brought out by these authors for this species were similar, in that the shorter fish at the end of the first year of life tended to grow more in the following year than did the longer first-year fish. The studies demonstrated further that the initial advantage of the longer first-year fish was not completely overcome. This type of compensatory growth was also found in the Green Bay herring (table 24), Previous investigators have examined the phe- nomenon of growth compensation by dividing fish into different length groups according to the first year's growth and comparing subsequent growth of these groups. It is not to be anticipated, how- ever, that these first-j^car groupings will retain their identities in subsequent years; that is, indi- vidual growth will vary sufficiently so that a new grouping on a similar basis in later years will show some exchange of fish between the original groups. In lake herring both previous and subsequent growth of fish of the same length in a particular year of life varied widely (table 25). For example, the 47 lake herring that were 7.0 to 7.4 inches long in the second year of life had ranged from 3.5 to 5.9 inches in their first year and from 8,5 to 10.9 inches in their third year. Because of the tendency for fish of a given length in a particular year of life to derive from fish of a considerable length range in earlier years and, in turn, to contribute to a wide range of length in subsequent years, it is to be anticipated that the growth of fish of different length groups will vary according to the 3'ear of life in which the grouping is made. This expectation is met by the data of table 24 in which length groupings of fish of a single age group are made on a similar basis (see caption of table) for each year of life. The maximum difference (difference between mean lengths of the terminal group) without exception was greatest for the year of grouping, and de- creased consistently in previous and subsequent years of life. The decrease from the year of grouping toward earlier years reflects the diverse origin of the fish with respect to their positions in the length distributions in those earlier years. Tlie decrease in the maximum difference in years of life following the year of grouping represents a tendency toward convergence of size. Further information on these growth relation- ships is to be had from the annual growth incre- ments of length shown at the right of table 24. Here it is seen that the increments in each year of life preceding the year of grouping tended to fall in the same order as in the grouping year itself, l)ut that in subsequent years the increments tended to fall in the reverse order. As a general biological phenomenon, growth compensation may reflect principles holding for LAKE HERRING OF GREEN BAY. LAKE MICHIGAN 111 Table 25. — Subsequent and/or previous frequency distribution of the calculated length of lake herring that had the same cal- culated length at the end of a particular year of life (Based on all age group III Ash of tbe 1950 pound-net collections] Year of grouping and calculated total length (inches) Length frequency at end of year of life— 1 2 3 1 2 3 1 2 3 I 2 3 1st year of life: 54 5 to *) 4 90 •> 5 to 5 9 101 65 6 *) to 6 9 5 22 12 9 6 1 17 40 30 2 1 3 23 51 18 2 2 1 7 to 7 4 1 5 28 26 4 2 & to K 4 » 6 15 19 10 3 4 17 44 20 5 2 10 35 41 10 2 1 90to94 2 21 23 10 S to 10 9 17 2 2d year of life: 1 4 22 17 3 1 12 40 23 5 1 9 30 51 28 1 4 .S to 4 9 6 2 18 26 4 7 to 7 4 47 7 5 to 7 9 81 120 9 16 16 5 1 2 21 40 16 2 56 6 56 46 11 1 10 10 to 10 4 29 16 - 1 3(1 year of life: 1 1 13 16 10 2 4 to 4 4 2 19 44 35 21 1 12 21 41 23 5 3 5 10 17 2 1 2 13 21 6 70to74 16 40 56 10 8 16 46 29 3 1 2 11 16 5 2 7 5 to 7 9 43 122 102 37 fish and also for other animals as well. Hile (1941, p. 305) stated that— A wealth of experimental evidence supports the view that among animals in general the inherent capacity for growth is lost chiefly through its exercise, and, conversely, the failure to grow does not entail necessarily the loss of the natural ability to grow. In support of this statement he cited the work of several authors on such widely separated groups as mammals, fish, salamanders, and insects. Hodgson (1929), on the other hand, demonstrated that compensatory growth could be a perfectly natural result of comparisons of fish of different age (fish that have the same number of anniili that were of different ages because they hatclied at different times during the season). Hodgson explained his view that growth compensation is "apparent" by comparing identical hypothetical growth curves that started at different points along the time axis.* Later Hile (1941) applied Hodgson's principle to the sigmoid growth curve of the rock bass to explain the variety of relations!iips among the annual increments of different yearling size groups. A similar use of the growth curve of the Green Bay lake herring is presented in figure 6. Here the two growth curves are identical but fish .1 hatched and started to grow at time 0^, whereas fish B hatched and started to grow at time Oa. At time ' Hodgson (1929) felt that a bimodal length-frequency distribution of first- year sea herring resulted from a long irregular hatching period and estimated that hatching extended over about 3 months. Hile (19.36) also attributed a bimodal first-year lenpth-frcquoncy distribution of cl.scoes In certain year classes in two Wisconsin laltes to irregular weather conditions during the hatching period that resulted in irregular and prolonged batching. It has been impo.ssible to learn anything about the hatching of lake herring in Green Bay. but it is believed that hatching may extend over a period of several weeks since spawning occurs over a period of 4 to 6 weeks. 112 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE Table 26. — Growth exhibited by lake herring that were the same length at the end of different years of life [Total length in inches] I I- O z 111 ^ ^^ / e ^' / c / 11 b 1 a d T T I ME T+l Fic.uBE 6. — The effects of differences in age (time of hatching) on the amount of growth during a later grow- ing season. T, which may mark the end of any growth period, fish A has attained length ac and fish B has at- tained tlie lesser length ab. During the interval from T to T+l fish A, which had expended more of its ability to grow at time T, added the incre- ment of length /fif which is less than the increment ef added by younger fish B. This explanation of growth compensation as an apparent phenomenon is based on tlie premise that all fish have the same growth curve. Under this concept, the growth of fish during a particular time interval depends principally on the size it had attained at the beginning of the interval. The data presented in table 26 shows that this assumption is essentially correct, for fish of the same lengtli at different ages tend to grow the same amount in tlie following year. In a review of Hodgson's (1929) treatment of growth compensation, Ford (193.3) offered the Length group and Num- ber of flsh Year of life at which computed lengths are grouped Length at end of year of life— Length increment year of capture 2 3 4 3 4 8.0 to 8.4 inches: 1949 207 128 133 / 81 \ 69 46 104 I 57 \ 56 { 1 { 201 ( ' \ 221 { 146 { 2^ i I { I 2 3 2 3 2 3 2 3 I 2 3 2 3 2 3 8.2 '8"2" "8."2' 8.6 ""8." 7" "8.' 7" "8." 6' 9.2 "9."i" "9.3' '"9.2" 9.7 8.2 9.7 8.2 9.8 8.2 10.0 8.8 10.0 8.8 10.1 8.8 10.2 8.7 10.4 9.2 10.3 9.2 10.6 9.2 10.5 9.3 "9.'8' "9.6" ""9.'7" io.'i" "io.o" io.'i' 'io.'i' 'io.'s" 'i6.'4' io.'e' io.r 1.5 ■'i.'s' "i.'e' 1.4 "i.l' "i'V "i.'e' 1.2 ■"i.'2' 'i.'s' "i.'s' 1950- 1951 . 8..'; to 8.9 inches: 1949 . 1950 1951- 1952 9,0 to 9.4 inches: 1949- 1950 1.1 1951- 1.2 1952.. 1.4 1.4 Unweighted aver- 1.39 1.35 criticism that Hodgson employed curves of iden- tical shape, although it is well known that growth may vary from individual to individual. Ford demonstrated that Hodgson's explanation could be supported from comparisons of growth along dissimilar curves starting at different points along the time axis. From the hypothetical curves of figure 7 it can be shown that dissimilar curves starting at the same point on the time axis will also exhibit growth compensation. This compensation depends on the fact proved earlier that size, not age, at the start of a period of growth determines the amount of growth that will be made during the period. The form of three of the five curves of figure 7 is iden- tical with that of the growth curves of figure 6, namely, OaCQ, OC, and Oabf. The curves Ocg and 06/ represent individual fish ^4 and B whose growth up to time T departed from the typical. Fish A grew more (ac) and fish B grew less (ab) at time T than the typical fish which would follow curve OC. Since, however, length is more important than age as a determiner of growth within a period (table 26), fish A may be expected subsequently to grow along the curve eg or, in other words, to follow the same course as a normal fish hatched at time LAKE HERRING OF GREEN BAY, LAKE MICHIGAN 113 I I- o z u Figure 7. — The effect of size at the start of a growing season on the amoui of growth during that season. 0.4. Similarly, the growth after time T of fish B should be that of a r .rmal fish that hatched at Ob. The compensatory effects of differences in the growth of these two typical fish (hatched at the same time) during the period T—T-\-\ is identical with the compensation between the two typical fish hatched at 0^ and Ob in figure 6. General growth in length Distorting influences of the negative correlation between individual length of life anti rate of growth make it impossible to establisli a general curve that might repres nt the growth history of a typical, or "avei, ^e," fish. Only growth of particular age groups can be shown. Curves in figure 8, based on data of all pound-net collections (table 17), are believed to be the most reliable means of representing the geneial growth of Green Bay lake herring taken in the commercial fishery. Age groups I, II, and VI are omitted from the data . IV V - III /^ - /^ 7 / / ./ 1 1 1 i 3 ACE Figure 8. — Calculated growth in length of age groups III. IV. and V of Green Bay lake herring as determined for all fish of these age groups taken in pound nets. 1948-62. because of the bias introduced by their almost com- plete absence from samples during some seasons, and because they are represented by small num- bers of fish. LENGTH-WEIGHT RELATION GENERAL RELATIONSHIP The variation of the volume of an object of con- stant shape with the cube of any linear dimension is a well known principle of mathematics. It can also be said that the weight of an object must vary with the cube of any linear dimension if the shape and specific gravity are both constant. If, however, the shape or specific gravity changes the relationship does not hold, but other relatively simple relationships ordinarily can be used to in- terpret the cha^-^es. The usefulness f the "cube law" in the study of the weight of animals was recognized by Herbert Spencer in 1871 according to a discussion of its application in this field by Thompson (1942). Hile (1936) reviewed the use of this principle in studies of the relation between the length and weight of fish. The condition coefficient "C" determined by the formula ('=WIU (C = the coefficient, U'=weight, and Z,=length) is widely employed by fishery workers as an index of changes in the form of fish 114 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE that result from such phenomena as maturation and release of sex products or variations in the amount of fat or flesh. If the cube relationship is maintained throughout life then C is an un- biased expression of condition and it is possible to compare the coefficients of fish of different length. Thompson (1942) pointed out, however, that, "* * * inasmuch as the animal is continually apt to change its body proportions during life, k [his sj^mbol for condition coefficient] also is continually subject to change." In this situation C becomes a function of length and the C values of fish of different length are not directly comparable as measures of departure from the "normal" for the stock. Hile (1936, p. 23S) stated that— Although the cube law does appear to apply to the length- weight relationship in some species * * *, these instances appear to be the exceptions, for the * * * inadequacy of the cube law in describing the length-weight relationship in fishes have been repeated by numerous investigators and on many forms of fishes. The situation is further complicated by the fact that not only does the length-weight relation de- viate from the cube law, but it is not the same for different populations of the same species and it varies from year to year within the same popula- tions (Hile 1936). The relation between length and weight in most populations of fish is represented satisfactorily by the formula W=cL", where Tr=weight, Z=length, and c and n are constants. However, since the relation between length and weight in a popula- tion varies with respect to sex, season, method of capture, and year of capture, as will be shown later, no single equation can describe the situation at all times and any general relationship that might be established is of necessity artificial. Nevertheless, a general length-weight equation based on all available data, regardless of sex, maturity, collecting gear, or season of capture, can be useful as an estimate of the average situation. An estimate of the length-weight relation of Green Bay lake herring based on all data is log H'-:— 2.4386-^3.0729 log L, where W equals weight in ounces, and L equals total length in inches. Data upon which this estimate was based are shown in table 27. The weights computed from the mean length of fish in each length group are the basis of the curve in figure 9; the empirical data are shown by dots. Comparisons of calculated and actual weights e 8 10 12 TOTAL LENGTH (INCHES) Figure 9. — Length-weight relation of the lake herring of Green Bay. The dots show the empirical data; the curve is the graph of the equation given in the text. prove that this formula does not describe the empirical data precisely. Calculated weights are generally less than actual weights for fish under 9 inches, greater for fish between 9 and 12 inches, and less for fish longer than 12 inches. A close fit was hardly to be expected in view of the known heterogeneity of the material. Few fish under 9 inches and over 12 inches were taken, and these were not equally represented in all seasons (table 7). This variation in representation to- gether with seasonal differences in weights of fish of the same length are responsible for the irregu- larities. SEASONAL CHANGES IN WEIGHT The study of seasonal changes in weight of Green Bay lake herring (table 28) is restricted to fish captured in the same calendar year (1949), in the same area (extreme southern Green Bay), and in the same gear (pound nets). In the 12 h^igth intervals represented by 3 or more fish on all three collection dates the October fish were heaviest in 11 and the May fish were lightest in 11. Febru- ary specimens were, of course, cliaracteristically intermediate (10 of 12 comparisons). Over the length range at which all dates were represented, the October specimens averaged 4.8 percent LAKE HERRING OF GREEN BAY, LAKE MICHIGAN 115 Table 27. — Relation between the total length and weight of Green Bay lake herring |AU collections combined] Table 28. — Seasonal changes in weight of lake herring taken in pound nets in southern Green Bay during 1949 [Weight In ounces] Total length (Inches) Number offish Weight (ounces) Empirical Calculated 5.8 to 5.9 1 4 2 6 8 S 5 11 5 4 12 7 17 16 12 11 15 21 28 45 137 211 328 431 495 497 503 376 206 146 103 59 39 24 17 15 6 6 3 1 3 3 2 1 1 1 0.90 1.07 1.05 1.16 1.26 1.36 1.48 1.62 1.86 1.86 2.15 2.47 2.48 2.76 2.77 2.85 3.19 3.33 3.32 3.73 3.98 4.16 4.45 4.64 4.97 5.19 5. 51 5.88 6.23 6.64 7.03 7.51 8.10 8.58 9.20 9.94 9.98 11.31 11.53 9.10 11.63 13.00 15.25 14.20 14.50 14.90 0.80 6.0 to 6.1 0.91 6.2 to 6.3 1.02 6.4 to 6.5 1 10 6.6 to 6.7 1.24 6.8 to 6.9 1 32 7.0 to 7.1 - 1 47 7.2 to 7.3 1.59 7.4 to 7.5 1 76 7.6 to 7.7 1.86 7.8 to 7.9 2 05 8.0 to 8.1 2 19 8.2 to 8.3- 2.38 8.4 to 8.5 2 57 8.6 to 8.7 - 2.76 8.8 to 8.9 ... 2 93 9.0 to 9.1 3 18 9.2 to 9.3- - 3.41 9.4 to 9.5 3 62 9.6 to 9.7 3 87 4. 11 10.0 to 10.1 4 37 10.2 to 10.3 - - 4.64 10.4 to 10.5 . . . 4 93 10.6 to 10.7 5 23 108 to 10.9..- -.- 5.52 5 84 11.2 to 11.3 - 6. 17 11.4 to 11.5 - - 6.51 11.6 to 11.7 6 87 11.8 to 11.9 - 7.22 12.0 to 12.1 7 69 12.2 to 12.3 - 8.04 12.4 to 12.5 - -.. 8.42 12.6 to 12.7 8 84 12.8 to 12.9 - 9.31 9 71 13.2 to 13.3 13.4 to 13.5 - . . . 10 73 13.6 to 13.7 11 10 13.8 to 13.9.-.- 11.58 14.0 to 14.1 12 19 14.6 to 14.7 - - 13 77 14.8 to 14.9 . . - 14 68 15.6 to 15.7 - 17 23 16.6 to 16.7.-.- - 20 83 above and the May fish 4.6 percent below the unweighted mean for the tliree dates. The February specimens were sliglitly (0.2 percent) above tiie mean. Seasonal changes in weights of fish are often associated with, and are used to follow, the de- velopment and release of sex products. Thomp- son (1942) showed a weight cycle for plaice fol- lowing the spawning cycle, but he pointed out that immature fish also experience a seasonal weight fluctuation similar to that of mature fish. These seasonal changes, he believed, indicate a cycle of relative well-being originating in the variation of conditions that influence the addition or removal of body fat or tissue. SEX DIFFERENCES IN WEIGHT Because of the demonstrated seasonal changes in weight, studies of sex differences in weight are best made on samples taken within a short period February 16 May 13 October 5 Total length (inches) Num- ber offish Aver- age weight Num- ber offish Aver- welght Num- ber offish Aver- age weight 7.8 to 7.9 1 1 3 2 1 4 7 3 4 8 12 27 34 30 41 51 14 12 9 7 3 2 1 1 1 1 1.80 8.0 to 8.1 2L10 8.2 to 8.3 1.97 8.4 to 8.5 Z35 8.8 to 8.9 . - 2.90 9.0 to 9.1 i 1 3 3 8 26 46 69 73 75 62 36 23 5 4 5 2.80 3.60 3.03 3.30 3.48 3.85 4. 15 4.27 4.53 4.82 5.05 5.45 5.67 6.34 6.20 7.02 2.20 9.2 to 9.3 1 2 7 26 50 73 66 34 32 22 15 9 3 3 2 2.90 3.45 3.57 3.86 4.01 4.30 4.45 4.71 5.00 5.42 5.68 5.85 6.23 6.76 6.65 3.22 9.4 to 9.5 3.45 9.6 to 9.7- 3.70 9.8 to 9.9 3.52 10.0 to 10.1. . . . 4. 11 10.2 to 10.3... 4.33 10.4 to 10.5 4 82 10.6 to 10.7 5. 18 108 to 10.9 5.27 11.0 to 11.1 11.2 to 11.3 5.70 5.98 11.4 to 11.5 6.30 11.6 to 11.7 . . 6.62 11.8 to 11.9... 7.12 12.0 to 12.1 7.61 12.2 to 12.3 8.06 12.4 to 12.5. 8.55 13.0 to 13.1 9.10 13.2 to 13.3 .... 9.30 13.4 to 13.5 12.20 14.0 to 14.1, 13.40 15.6 to 15.7 1 14.50 of time. Actually the comparisons offered by the data in table 29 are based on collections of single days. On none of these dates were sex differences large. The weights of male and female lake herring of corresponding length were nearly the same in February (males 0.5 percent lighter than females). Females were the lighter in May (1.8 percent) but were heavier in October (3.4 percent). Sex differences probably are greater at the time of spawning in the latter part of Xovember; un- fortunately, adequate samples were not available for study of this point. Carlander (1945) found no significant difference in condition coefficients of male and female tullibee from Ijake of the Woods. Direct comparison of weights of male and female tullibee from Gull Lake (Eddy and Carlander, 1942) showed the females to be slightly heavier for their length than the males, but the difference was small. These authors did not consider possible seasonal varia- tions in their presentation. Two of four popula- tions of ciscoes in northeastern Wisconsin lakes (collections were made only during the summer) showed no differences in weigiit between sexes; in the other two stocks the males were the heavier in one and the females were the lieavier in the other (Hile 1936). Van Oosten (1929) found little difl'erence between average condition coefficients 116 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE Table 29. — Weights of lake herring by sex and location taken in pound nets in southern Green Bay in 1949 [Weight in ounces] February 16, 1949 (Schumachers Point) May 13, 1949 (Pensaukee and Suamlco) October 6, 1949 (Pensaukee) Total length (inches) Males Females Males Females Males Females Number offish Average weight Number offish Average weight Number offish Average weight Number offish Average weight Number offish Average weight Number offish Average weight 7 8 to 7 9 1 1 3 2 2 1 1.80 g.OtoSl 2.10 8.2 to 8.3 1.96 8 4 to 8 6 3.35 8.6to8.7 -- 2.30 8.8 to 8.9 2.90 90to9.1 1 2.80 1 2 3 1 3 2 6 9 11 19 19 17 4 5 3 2 2.20 3. 55 3.40 4.30 3 47 4.10 4.05 4.72 5.10 5.15 5.70 5.83 6.07 6.40 6.63 7.70 9 2 to 9 3 1 2 4 21 39 48 37 22 21 12 12 7 3 3 2 2.90 3.45 3.47 3.86 4.01 4.30 4.44 4.65 4.97 6.38 5.75 5.94 6.23 6.76 6.65 1 1 1 2 11 21 33 29 38 23 18 5 1 2 3 3.60 3.20 3.60 3.50 3.82 4.11 4.34 4.55 4.88 6.16 6.41 5.90 7.10 6.80 7.20 2 4 2 1 t 18 23 11 22 34 10 7 6 5 3 2 1 1 2.90 94 to95 2 2 6 15 25 36 44 37 39 18 18 •1 2 2.95 3.20 3.48 3.86 4.17 4.21 4.52 4.76 4.99 6.48 6.61 6.16 6.60 5.70 3.60 9.6 to 9.7 - 3 5 11 25 29 12 11 10 3 2 3.70 3.86 4.00 4.32 4.48 4.82 5.07 6.48 4.43 5.55 3 40 9.8 to9.9. 3.70 10.0 to 10.1 4.11 10.2 to 10.3 4.61 10 4 to 10 5 4.88 10.6 to 10.7 5.23 10.8 to 10.9. 5.46 11 to 11.1 5.71 ll,2toll.3 -- --- 6.05 11 4 to 11.5 6.40 11.6 to 11.7 6.78 11 8 to 11 9 7.41 12 to 12.1 7.58 12 2 to 12 3 8.07 12 4 to 12 5 8.55 13 to 13 1 9. 10 13 2 to 13 3 9.30 1 12.20 14 to 14 1 I 13.40 1 14.50 of male and female lake herring of the spawning run (October-November) in Saginaw Bay (all lengths combined). Seasonal variations in differ- ences of weight between the sexes in related species have been reported by Jobes for Levcichthys reighardi (1943), L. alpenae (1949a), and L. hoyi (1949b) , and by Deason and Hile for L. kiyi (1947). Comparisons by Bauch (1949) of the mean condi- tion coefficients of Coregonus albnla of Mochelsee showed that females were slightly heavier than males during all seasons. In spawning-run samples of the same species from Keitelesee (Jarvi 1920) ripe females were heaviest for their length and spent females were lightest (only slightly lighter than males). ANNUAL DIFFERENCES IN WEIGHT Annual fluctuations in the length-weight relation of Green Bay lake herring captured at the same time of year (January or February) in 1949 to 1952 generally were small (table 30). Weights of fish of the same length showed an upward trend from 1949 to 1952. The amount of change from year to year is indicated roughly by the following Table 30. — Weights of lake herring taken in pound nets during February 1949-51 and January 1952 [Weight in ounces] 1949 1960 1951 1952 Total length (inches) Num- ber of fish Aver- age weight Num- ber of fish Aver- age weight Num- ber of fish Aver- age weight Num- ber of fish Aver- weight 8.0 to 8.1 1 1 1 1 2 1 9 13 29 40 81 61 78 53 14 10 6 4 2 2 2.40 2.60 2.60 2.80 3.60 3.30 3.70 3.88 4.21 4.60 4.71 5.02 5.16 5.41 6.71 6.17 6.37 6.62 7.42 7.80 8.55 8 6 to 8 7 8 8 to 8.9 2 2 3 5 7 27 48 74 101 77 62 43 22 19 3 5 2.30 2.45 3.13 3.02 3.56 3.71 4.01 4.35 4.67 4.79 6.00 6.30 5.55 5.87 6.80 6.46 9.0 to 9.1 9 2 to 9.3 1 2 7 26 50 73 66 34 32 22 15 9 3 3 2 2.90 3.45 3.57 3.86 4.01 4.30 4.46 4.71 6.00 6.42 5.68 5.85 6.23 6.76 6.65 9.4 to 9.5 2 2.60 9 6 to 9 7 9.8 to 9.9 3 3 2 7 22 30 38 29 19 11 10 1 2 1 2 4.03 10.0 to 10.1 10.2 to 10.3 10.4 to 10.5 10.6 to 10.7 10.8 to 10.9 11.0 to 11.1 11.2 to 11.3 11.4tQll.5 11.6 to 11.7 11.8 to 11.9 12 to 12 1 4.03 4.70 4.80 6.04 6.17 i.K 5.74 6.12 6.20 6.60 6.80 12.2 to 12.3 7.50 7.90 6.45 12.4 to 12.5 7.80 12 6 to 12.7 7.80 12 8 to 12 9 8.70 13 to 13 1 2 10.10 13 2 to 13 3 11.00 14 to 14 1 1 11.40 14.20 Mean deviation from average percent. - -2.3 -1.8 1.3 1.7 LAKE HERRING OF GREEN BAY, LAKE MICHIGAN 117 mean percentages of deviations from the average weight for all years: 1949, —2.3 percent; 1950, — 1.8 percent; 1951, 1.3 percent; and 1952, 1.7 percent. This period of increasing weight was also one of generally improving growth rate (table 22). Hile (1936) found that the length-weight relation and condition coefficient varied from year to year in three of four populations of ciscoes in north- eastern Wisconsin lakes. Annual differences in the length-weight relation were reported by Deason and Hile (1947) for Leucichthys Iciyi and by Jobes for L. reighardi (1943), L. alpenae (1949a), and L. hnyi (1949b). INFLUENCE OF METHOD OF CAPTURE ON WEIGHT Discussions of seasonal and annual fluctuations, and sex differences in the length-weight relation have been based entirely on fish taken from pound nets. Gill-net samples were omitted from these comparisons because of the bias to length-weight data introduced by gill-net selectivity. Farran (1936) treated this problem in detail and estab- lished limits of selectivity (in terms of length and girth) of different sizes of mesh of gill nets in cap- turing marine herring. Deason and Hile (1947) demonstrated that within a sample of kiyi from Lake Michigan that was homogeneous as to age, sex, and locality and date of capture, the coeffi- cient of condition decreased with increase in length of fish taken by gill nets of the same mesh size but increased in fish of the same length with increase of mesh size. Although materials for the study of effects of gear selection on length-weight data in the Green Bay lake herring are scanty, those that are avail- able (table 31) demonstrate conclusively that gill nets tend to take heavier fish than do pound nets operating in the same area and season, but because of the small numbers of fish on which the individual averages are based, a number of exceptions oc- curred. The records for females taken during the spawning season show almost no difference be- tween samples from the two gears. The extent of the bias in the remaining comparisons is suffi- ciently great, however, to make exclusion of the gill-net samples desirable in detailed studies of the length-weight relation. Table 31. — Weights of lake herring taken in gill nets and in pound nets at different times of the year, 1950 and 1961 [Weight in ounces) November February Total length Oill net 1 Pound net ' Om net » Pound net ' (inches) Num- ber of fish .Aver- age weight Num- ber of ash Aver- age weight Num- ber of fish Aver- age weight Num- ber of fish Aver- age weight Males: 9.7 to 9.9 2 3 8 12 13 4 2 4.00 4.13 4.83 5.05 5.51 5.95 6.00 1 3 4 8 26 19 4 3 1 3.90 4.56 4.65 5.25 5.63 5.98 6.47 6.56 7.70 1 3 5 17 21 16 4.00 10.0 to 10.2 10.3 to 10.5 10.6 to 10.8 10.9 to 11. 1 11.2 to 11.4 11.5 to 11.7 1 2 11 13 13 10 4 1 1 1 4.70 5.10 5.32 5.69 5.86 6.60 6.70 7.40 8.60 9.00 3.86 4.74 5.10 5.30 5.61 11.8 to 12.0 12.1 to 12.3 12.4 to 12.6 1 7.90 12.7 to 12.9 Total or aver- 57 1 1 5.99 2.30 2.30 4.10 44 5.16 69 5.66 64 5.24 Females: 7.6 to 7.8 . 8.2 to 8.4,. 9.1 to 9.3 9.7 to 9.9 -. 1 7 8 16 22 5 1 4.10 4.38 4.90 5.30 5.67 6.40 6.30 1 2 6 20 32 22 8 2 3 2 3.60 4.60 4.95 5.12 5.50 5.82 6.43 7.25 8.36 8.05 10.0 to 10.2 10.3 to 10.5_ 10.6 to 10.8 10.9 to 11. K ... 11.2 to 11.4 11.5 to 11.7 11.8 to 12.0 1 1 4 5 7 9 5 9 1 3 1 1 5.20 5.30 5.65 5.68 5.92 6.76 7.20 7.67 8.00 8.80 9.40 10.50 3 18 31 42 12 12 4 1 1 4.50 4.72 4.86 5.23 5.44 6.16 6.97 12.1 to 12.3. 12.4 to 12.6 1 8.30 8.00 9.20 12.7 to 12.9 2 9.35 13.0 to 13.2 1 9.40 13.6 to 13.8 Total or aver- SO 6. 65 63 5.54 98 5.67 125 5.30 ' Collected from a 2?8-lnch-mesh gill net at Oconto on November 30, 1950. 2 Collected from a pound net at Fox on November 29, 1950. > Collected from a 25s-lnch-mesh gill net at Pensaukee on February 20, 1951. * Collected from a pound net at Schumachers Point on February 22, 1951. GENERAL GROWTH IN WEIGHT The differences in weight according to sex, season, and year of capture detract from the use- fulness of the general growth curves of the Green Bay lake herring. The best means of depicting growth is to compute weights for the calculated lengths of the best-represented age groups for all pound-net data (table 17). Weights for age groups III, IV, and V calculated from the general length-weight relation (p. 114) are given in table 32. Growth curves for these age groups are given in figure 10. 118 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE u z «04 I O ^3 I- O u V / IV / III / // /// / - /// - /// ■J I I 2 3 4 5 6 AGE Figure 10. — Calculated growth in weight of age groups III, IV, and V of Green Bay lake herring as determined from calculated lengths for all fish taken from pound nets, 1948-52, and the length-weight relation for all fish of these age groups. Table 32. — Calculated growth in weight for the Green Bay lake herring of age groups III, IV, and V [Calculated from the general length-weight relation, p. 114, and lengths of fish taken in pound nets In 1948-52, table 17, p. 104] Age group Weight (ounces) at age— 1 2 3 4 5 III 0.65 .61 .51 2.25 2.01 1.71 4.18 3.68 3.01 IV 5.15 4.44 V-. 5 77 REPRODUCTION AND EARLY GROWTH SEX COMPOSITION As is common among fish, data on sex composi- tion in lake herring populations are highly variable. Some factors that may contribute to variability of sex composition in samples from a population are: /. Segregation of the sexes through various periods of the year including segregation resulting from sex differences in age and size at maturity. 2. Differences in mortality (natural or fishing) between the sexes. S. Gear selectivity in relation to sex differ- ences in activity and morphology. To evaluate any of tliese factors would be diffi- cult, particularly since they are interrelated and some or all of them may affect the sex composition of a sample. Reports of various authors on different popula- tions of lake herring (table 3.3) show sex composi- tion, expressed as percentage of females, ranging from 29 percent in Blind Lake (Cooper 1937) to 73 percent in Trout Lake (Hile 1936). The Blind Lake collection was made during the spawning period but the paucity of females is not character- istic of spawning fish as may be seen by the sex composition of other samples collected during the spawning period — in Swains Lake (67 percent) and Saginaw Bay (51 percent). Six out of 1 1 lake herring populations for which data have been published on the change of sex composition in relation to age (table 33) show a rise in the proportion of females with increase in age (Clear I^ake, Gidl Ijake, Lake of the Woods, Muskelliinge Lake, Swains Lake, and Trout Lake), 2 populations show a downward trend (Blind Lake and Saginaw Bay), and 3 exhibit no clear trend (Irondequoit Bay, Lake Nipissing, and Silver Lake). The 6 populations exhibiting an increase in the percentage of females with age were col- lected with gill nets and 1 (Swains Lake) was sampled exclusively during the spawning period. Of the 2 populations with a downward trend, 1 was sampled with pound nets (Saginaw Bay) and the other with gill nets (Blind Lake), and both sets of data were based on spawning-run collec- tions. One of the 3 populations showing no trend was sampled with pound nets (Irondequoit Bay) and the other 2 were sampled with gill nets, and all represent samples from more than 1 month and year. It is obvious from these comparisons that the relation of sex composition to age as reported for different stocks is not clearly influenced by collecting gear or sexual activity at time of collection. Some information on possible sources of bias in determining the sex composition of a population is brought out in the Green Bay data on fluctua- tions in the sex ratio according to age, gear of collection, and depth, season, and year of capture. In pound-net samples, which made up the bulk of the Green Bay collections, the percentage of females was consistently higher in February than during other months of the year, and since no trend was shown in sex composition during the other months, the data for all but the February samples are combined in table 34. This seasonal LAKE HERRING OF GREEN BAY, LAKE MICHIGAN 119 Table 33. — Changes in sex composition icilh age for different lake herring populations [Number of fish in parentheses] Slate and body of water Percentage females in age group — All ages Gear used Investigator I II III IV V VI VII VIII IX x+ Michigan: 100 (1) 67 (3) 35 (23) 55 (11) 29 (66) 54 (818) 24 (38) 50 (1.434) 20 (5) 52 (112) 59 (63) 38 (13) 56 (350) 47 (39) (2) 53 (160) 78 (368) 30 (10) 50 (539) 64 (22) 65 (342) 63 (38) 37 (43) 55 (293) 45 (20) 20 (10) 45 (124) 71 (24) 71 (168) 67 (12) 57 (68) 49 (255) 50 (26) (1) 42 (19) 68 (28) 80 (10) 100 (4) 59 (76) 36 (67) 66 (50) 28 (162) 51 (2, 950) 67 (84) 63 (658) 54 (421) 57 (494) 53 (1. 524) 51 (440) 58 (861) 55 (496) 73 (1,101) gill pound gUl -..do- ...do pound gill ...do ...do - -..do ...do Cooper (1937). 20 (5) 100 (1) Van Oosten (1929), 100 (3) 100 (1) Brown and Moflett (1942). Minnesota: Gull Lake (2) 49 (101) 39 (64) 53 (156) 47 (102) 57 (472) 62 (26) 62 (97) 17 (24) 54 (120) 66 (216) 55 (334) 48 (95) 60 (361) 56 (86) 67 (520) Eddy and Carlander (1942). 48 (80) (2) 64 (11) 76 (21) 68 (31) 100 (1) 92 (13) 75 (4) (1) 50 (2) 60 (5) 100 (4) Carlander (1945). Stone (1938). Ontario" Lake Xipissing Fry (1937). Wisconsin: Clear Lake 42 (69) 50 (26) 52 (66) 50 (2) Hlle (1936). Do. 56 (133) 93 (80) 67 (24) 92 (12) 100 (1) 100 (4) Do. 80 (5) 100 (2) 33 (3) Do. Table 34. — Sea; composition of lake herring taken in pound nets, 1948-5B [Number of fish in parentheses; males at left, females at right] Time of collection Percentage females in age group— I II III IV V VI VII All fish 1 1948: May .. ... ....... 75 (1:3) 60 (57:84) 74 (11:31) 61 (112:172) 64 (20:36) 46 (153:128) 71 (9:22) 47 (31:27) 71 (2:5) 55 (50:60) 67 (85:171) 57 (157:206) 61 (148:230) 47 (114:102) 57 (148:200) 43 (107:82) 48 (81:74) 71 (2:5) 68 (15:32) 60 (17:25) 54 (31:37) 45 (11:9) 56 (24:31) 19 (21:5) 73 (4:11) 58 1940: (110:152) 68 100 (0:2) 63 (7:12) 33 (2:1) 50 (2:2) (2:0) 100 (0:1) 100 (0:1) (1:0) (111:234) 59 1950: (298:426) 60 43 (4:3) 50 (10:10) 100 (0:1) 44 (15:12) (201:306) 46 1951: (294:252) 59 100 (0:2) 100 (0:1) (182:257) 42 1952" January (178:130) 51 (90:92) 1949-52' January-February 100 (0:1) 53 (33:37) 69 (42:94) 54 (352:411) 59 (462:675) 51 (428:450) 60 (74:111) 46 (51:44) 50 (3:3) 33 (4:2) 60 1948-51: May-December 63 (4:7) 100 (0:1) (584:889) 52 (880:960) ' Includes flsh of unknown age. diflFerencc in th(^ percentage of females appears in the data for individual age groups as well as in the data for all ages combined. The percentage of females in samples of lake herring taken from pound nets also showed a clear tendency to decrease during the period 1949 to 1952 (table 84). This trend is present in the best-presented age groups (III and IV') as well as in tlie data for all ages combined in both the Januarv-P\'l)ruarv samples and the samples from the remaining montlis. The change in sex composition witli increase in age of lake herring taken in pound nets was irreg- ular, but a downward trend in the percentage of females is evident in most series (table 34) and is conspicuous where data of all years for compara- able periods have been combined (bottom of table). This trend would suggest that young females might be taken in the pound-net fishery at a higher rate than young males. A sex differ- ence in mortality of this kind should result in a progressive reduction in the proportion of females within a year class. That this expectation is fulfilled consistentlv in the January-February 120 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE collections is demonstrated by the following tabulation of percentages of females in samples of four different year classes at various ages (where represented by 25 fish or more). Table 35. — iSex composition of lake herring taken in gill nets, 1948-52 [Number of flsh In parentheses; males at left, females at right] Year class Percentage females and age group In— 1949 1950 1961 1952 67 (IV) 74 (III) 54 (V) 61 (IV) 64 (HI) 1946 66 (V) 57 (IV) 71 (III) 1947 48 (IV) The corresponding tabulation for collections made in months other than January and February demonstrates a similar trend but does contain one exception, the V-group of the 1944 year class. Year class Percentage females and age group In— 1948 1949 1950 1952 1944 55 (IV) 60 (III) 68 (V) 57 (IV) 61 (III) 1946 47 (IV) 46 (III) 19 (V) 1947 43 (IV) In gill-net collections the percentage of females varied widely from sample to sample (table 35). Although the available data are insufficient for a study of annual and seasonal trends, they offer no evidence of disagreement with the trends established in pound-net data. The change in sex composition with age of gill-net caught fish, however, is the reverse of that of fish taken by pound nets. The gill-net samples show a clear tendency toward a higher percentage of females with increasing age. This progressive destruction by gill nets of females in the older age groups should tend to counteract the effect of pound nets in cropping younger females at a faster rate than males. The combined effects of the selective destruction of the two fishing gears in determining differences in sex composition with season and age cannot be evaluated with data at hand. It is clear, however, that females are cropped more heavily than males during the winter (January-February) fishery by both pound nets and gill nets. The effects of this destruction of females are counteracted in part by the greater destruction of males in the remaining months of the year. Records of the sex composition of samples of lake herring taken at various levels between the surface and bottom (see description of oblique Time of Percentage females in age group— All ages coUectlon ' I II in IV V VI 1948' October 33 (4:2) 40 (3:2) 73 (22:58) 43 (44:33) 100 (0:5) 30 (47:20) 20 (4:1) 53 (8:9) 42 (88:64) 74 (15:43) 62 (8:13) 56 (58:75) 50 (4:4) 44 (74:57) 68 (10:21) 42 (64:39) 63 (3:5) (2:0) 63 (10:17) 71 1960: November- .- 1951: 100 (0:2) (44:108) 47 (57:50) 5 „9 33 (2:1) (69:%) 33 1962: 53 (8:9) 100 (0:1) (64:26) 46 July (87:70) 61 100 (0:1) 75 (1:3) (19:30) 43 (143:109) AU dates 100 (0:2) 40 (9:6) 47 (213:190) 53 (223:252) 69 (24:34) 100 (0:1) 51 (473:491) 1 Collection from commercial gUl nets— 1948, 1960, 1951; collection from experimental gill nets— 1962. gUl-net sets in Vertical Distribution in Green Bay, p. 128), yielded no evidence of segregation of the sexes according to depth in June or July, but they indicated a strong tendency in October toward a higher percentage of females in the deeper strata than in the shallower (table 36). This trend was much stronger in samples from nets fished in 60 feet of water than in 90 feet (fig. 11). 30 ^S 60 DEPTH (FEET) Figure 11. — Sex composition of lake herring taken at vari- ous depths in October 1952 in 2-inch-mesh experimental gill nets set obliquely from surface to the bottom. Open circles indicate the data for 60-foot stations and solid circles the data for 90-foot stations; the regression lines were fitted by least squares. LAKE HERRING OF GREEN BAY. LAKE MICHIGAN 121 Table 36.- — Sex composition of lake herring taken al various depths in experimental S-inch-mesh gill nets in 195S (Number of fish In parentheses] I Month, depth, and station Date taken Percentage females at— All depths 0-15 feet 15-30 feet 30-45 feet 45-60 feet 60-75 feet 75-90 feet June: 60 feet: K 12 12 11 SO (4) (1) SO (4) too (1) 67 (6) 71 (17) SO (10) 63 (8) 60 (25) 63 (32) 58 (19) L 63 (0) (46) 90 feet- J 48 (23) 47 (15) 54 (6) (81) All depths - . - .._ 50 (4) 50 (6) (1) 64 (33) 38 (8) SO (4) 35 (31) 73 (30) 100 (1) 40 (5) 44 (9) 62 (65) 80 (10) 33 (6) 38 (16) 63 (30) 48 (23) 47 (IS) 58 July: 60 feet: C 24 22 21 21 27 22 21 (146) 58 (0) (19) H 40 CO) (1) (0) 33 (3) 44 (25) (10) K 35 (SI) L 61 (0) (85) 90 feet: D. .- (1) (2) 43 (21) SO (4) SO (2) 67 (27) SO I "(6) (0) "(oj 40 (15) 56 (18) (6) 38 J... (0) 100 (1) (0) 100 (2) (24) 56 (78) All depths-- so (2) 47 (15) 43 (44) 38 (37) 33 (40) 27 (30) 35 (49) 45 (11) 33 (40) 23 (30) 45 (31) 51 (88) 54 (95) 38 (24) 64 (33) 52 30feet:A 22 22 22 24 25 25 23 24 25 (273) 47 (0) 100 (2) 42 (36) 18 (40) 42 (26) 33 (30) 50 (8) 33 (40) 33 (30) (IS) 40 feet: B>..- _ 46 (46) 60 feet: C 44 (41) 57 (35) 60 (30) SO (30) 62 (29) 64 (25) 59 (44) 60 (30) 45 (143) H 40 (140) K,... - 48 (130) L 43 (139) 90 feet: D 47 I . .. (0) 43 (40) 37 (30) (0) 53 (57) SO (28) (0) 38 (8) 47 (30) (6) 100 (2) 48 (31) (19) 42 J (187) 40 (179) All depths 35 (296) 34 (212) 48 (206) 57 (213) 45 (38) 52 (33) 43 (998) • See figure 1 for location. ' Depths intervals 0-20 and 20-10. Despite the clear-cut change in sex composition with increase of depth, the vaHdity of an assump- tion that sexes are segregated according to depth in October is questionable. Since the gill nets used to obtain these collections were stationary the activity of the fish was a primary determinant of the number of fish taken by them. Accordingly, it is possible that changes in sex composition with depth do not reflect a corresponding difference in the actual relative abundance of males and females but that they are merely "apparent changes" traceable to sex differences in activity. In other words, the males may have been much more active than the females near the surface, whereas the activity of the sexes may have been equal or nearly equal at the greater depths. No evidence on the question of sex differences in activity is available from the present study or from published reports on the lake herring. Evidence has been published, however, that the males of the related kiyi of Lake Michigan become much more active during the spawning period (Hile and Deason, 1947). If a similar behavior is assumed for the lake herring, and if it is assumed further that the heightened activity of males starts in advance of the spawning period and that the fish near the surface are the ones closest to the spawning state (the lake herring is a pelagic spawner), then sex tlifferences in activity rather tlian true segregation can explain the relation of sex composition of lake 122 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE herring to depth in October samples which were taken about 3 weeks before spawning starts. AGE AND SIZE AT MATURITY A lake herring was considered immature if it was not in spawning condition when captured during the spawning season, or if the state of the gonads indicated that it would not spawn during the next spawning period following its capture. As most small lake herring captured in Green Bay were taken within a few months before the spawn- ing period, at a time when all mature fish had well-developed gonads, little difficulty was ex- perienced in distinguishing the immature individuals. Published statements as to the age at which the lake herring matures frequently have been indefinite because of considerable individual varia- tion among fish and because of questionable dependability of samples as a result of gear selection or segregation on the basis of maturity. Hile (1936) suspected that his estimates of per- centage of maturity in the younger age groups were too high if the faster-growing fish of each age group matured first, since his gill nets did not take the smaller members of those age groups. Van Oosten (1929), who sampled only fish of the spawning run, felt that since immature fish did not participate in spawning activities they were not properly represented in the samples. A summary of published data on the maturity of lake herring (table 37) shows that the age at which most fish mature in different populations varies from I to IV. Although lake herring maturing in the first jear of life (age group 0) have never been reported, maturity in the second year (age group I) is common. The reason for later maturity in some populations is not clearly understood . The Green Bay collections contained relatively few immature lake herring, all of which were in age groups 0, I, and II (table 38). The two 0-group fish taken (one male and one female) were immature. In age group I, 32 percent of the males and 1 1 percent of the females were mature. By the next year (age group II) most fish of both sexes had reached maturity (97 percent of the males; 88 percent of the females). This tendency for males to mature sooner than females was also found in tlic lake lierring of Saginaw Bay (Van Oosten 1929) and Irondequoit Bay (Stone 1938). The three 2-year-old ciscoes taken in Lake Ontario by Pritchard (1930) were all mature females. The average lengths of mature and immature fish indicate that the larger members of an age group are more likely to be mature (table 38). Table 37. — Age at which lake herring of different popula- tions reach sexual maturity (Arranged according to age at maturity] Age group in which— Body of water Few flsh mature Some fish mature Most or all flsh mature Investigator Clear Lake, Wis I n II II II II III III III IV IV IV Hile (1936). Green Bay, Lake Michigan I I I I Present work. Carlander (1945) Saginaw Bay, Lake Huron. Trout, Silver, and Muskel- lunge Lakes, Wis. Lake Erie .. - Van Oosten (1929). Hile (1936). Clemens (1922). Irondequoit Bay, Lake Ontario. Blind Lake, Mich '11 . II Stone (1938). Clemens (1922). Cahn (1927). Lake Ontario II III III Pritchard (1931) Dymond (1933). Manitoba Lakes Bajkov (1930). Table 38.- -Relations among age, lerigth, and sexual maturity in the lake herring of Green Bay [Total length in inches] Mature Immature Percent- Age group ' Number of flsh Total length Number offish Total length age mature Males: 1 17 1 1 16 4 6.0 6.9 8.0 5.8 7.8 8.2 I 8 33 8.2 9.9 32 II 97 Females: I . . 2 30 8.6 9.3 11 II _ 88 > All flsh older than age group II were mature. HATCHING AND EARLY GROWTH Almost nothing is known about the incubation, hatching, and early development of lake herring in nature. Cahn (1927) collected unhatched eggs in Lake Oconomowoc, Wisconsin, in March, but had no positive evidence as to the time of hatching. Pritchard (1930) observed that hatching takes place during April and early May in the Bay of Quinte, Lake Ontario, and he made daily collec- tions of the growing fry from May 9 to June 1. These fry were found among reeds in shallow- water areas of protected bays, but apparently they moved toward the open water as they grew. On June 1 when the last individuals were collected, they were 20 millimeters long. After that date tliey could not be located again. Greeley and Greene (1931) collected young-of-the-year lake LAKE HERRING OF GREEN BAY, LAKE MICHIGAN 123 herring in the St. Lawrence River near Ogdensburg, N. Y., on June 6, 17, and 18, and at Waddington, N. Y., on June 28, in 1930. Since adult lake herring are unknown in the river, it is presumed that these fish came 78 miles downstream from Lake Ontario. The lengths of these young herring on different dates of collection were as follows: Date Number or ash Length Average Range June 6 June 17, 18 15 142 76 21 mm 28 mm 36 mm 18 to 28 mm. 24 to 32 mm June 28 The mean length of 21 millimeters of the June 6 collection corresponds closely with the length of 20 mm. recorded by Pritchard (1930) on June 1. Cahn (1927) took three young of the year with an average length of 62.5 mm. in a gill net fished on the bottom at 52 feet in Lake Oconomowoc on June 20, 1922. Fry (1937) caught 0-group ciscoes in the region of the thermocline in Lake Nipissing during late August 1933 to 1935. Hile (1937) found 17 young lake herring (average length, 65 mm.) washed upon the shore of Trout Lake during late summer. Reighard (1915) re- ported similar recoveries of young in Douglas Lake and Ward (1896) found small lake herring washed up on the shore of Lake Michigan follow- ing storms. Records of a few recoveries of small lake herring from shallow-water areas of the Great Lakes are on file in the Fish Division of the Mu- seum of Zoology, University of Michigan. Knowledge of the distribution and habits of young-of-the-year lake herring is scanty in Green Bay also. In spite of a constant lookout for them during all field work and attempts to locate them with midwater and bottom trawls during the sum- mer of 1952 only two young-of-the-year lake her- ring have been taken from Green Bay. Botli were captured in a 1 -inch-mesh gill net from 17 fathoms of water off Gills Rock on December 12, 1951. One was a male 6.0 inches long and the other a female 5.8 inches long. Otter trawls of the same construction as those used in a search for small lake herring in Green Bay caught large numbers of yearling lake herring in Lake Superior in 1953 (often more than 1,000 in a 10-minute tow). The best catches were made at 5 to 15 fathoms in the Apostle Islands area near Bayfield, Wis., and along the southeastern shore of the Keweenaw Peninsula. These collections have not yet been studied, but examination of a few specimens showed that they were just starting their second year of life. Young-of-the-year lake herring 10 to 12 mm. long were taken in surface plankton tows on May 29 and 30 near Bayfield, Wis. These fry match the descriptions by Prichard (1930) and Fish (1932) of lake herring of the same length from Lakes Erie and Ontario. Further evidence that fry of the genus Levcichthys may be pelagic was obtained wlien fry of either L. hoyi or L. reighardi (my tentative identification) were collected by the author with a dip net in open water on Lake Michigan near North Manitou Island on July 30, 1952. FECUNDITY The number of eggs produced by female lake herring varies widely both within and between populations. Jordan and Evermann (1902) and Bean (1902) carried similar accounts of what must be the same fish — a 2K-pound female tullibee from the "western territories of Canada" — that held 23,700 eggs. Cahn (1927), using the volumetric method, estimated the number of eggs of a 465- gram (about 1 pound) female from Lake Ocono- mowoc at 15,238. Bajkov (1930) stated that the tullibee of the Canadian prairie provinces carry 15,000 to 20,000 eggs. Brown and Moffett (1942), using a partial- weight method, estimated the number of eggs in ovaries of 9 ciscoes from Swains Lake. The results of their study were as follows: Average Range Number of eggs 30,328 23,272 to 37,272. 16.7 In 1S.2 to 16.2 In. Weight offish 1.721b 1.48 to 1.861b. No correlation was found between number of eggs and size or age of these fish. Scott (1951) also used the partial-weight method to estimate the egg count of 12 Il-group and 6 Ill-group ciscoes from Lake Erie. His findings are summarized as follows : Age group II: -N'umber of eggs Total length of flsh ' Weight of fish Age group III: Numner of eggs Total length of fish ' Weight of flsh Average 29.225.. 13.4 In. 1.181b.. 23,017.. 15.3 in.. 1.65 lb- Range 16,000 to 42,500. 11.7 to 14.4 in. 0.65 to 1.50 1b. 14.200 to 38,600. 13.8 to 1(1.6 In. 0.06 to 2.21 lb. ' This paper gave only standard lengths. Estimates of total length In this stock have been based on the assumption that the ratio of total lengtb to standard length was 1.19— a value near the middle of the range o( conversion factors listed by Carlander (1950). 124 FISHERY BXJLLETm OF THE FISH AND WILDLIFE SERVICE Scott found that the number of eggs tended to increase with length and weight of the female. He pointed out, however, that the apparent decrease in the number of eggs with increasing age of the fish, as shown by his data, may be in error, since all age group III fish were ripe when collected and unknown numbers of eggs were lost in handling them. Stone (1938) estimated (by the volumetric method) the number of eggs of 104 Irondequoit Bay lake herring to average 24,095; the mean length of these fish was 13.4 inches. The average number of eggs per fish in the different age groups ranged from 13,723 in the 2-year-olds (average length, 11.9 in.) to 48,999 in the 8-year-olds (aver- age length, 16.7 in.). The number of eggs was estimated by the dry- weight method for 72 Green Bay lake herring. This method was developed by Paul H. Eschmeyer and George F. Lunger, of the Service's Great Lakes Fishery Investigations, in studies of the fecundity of lake trout; they have not pub- lished an account of the procedure. The general procedure with lake herring ovaries (which differs somewhat from that followed by Eschmeyer and Lunger for lake trout) is as follows: The formalin-preserved ovaries are broken up thoroughly and the larger pieces of connective tissue are removed; the remaining materials are dried at 60° C. until there is no further weight loss; a sample of 100 eggs is removed and weighed (weighing is facilitated if the dried material is allowed first to reach moisture equilibrium with the atmos- phere) ; the total number of eggs is computed from ovary weight and sample weight. The dependability of the method was tested by making 38 estimates from 100-egg samples of 19 ovaries for which actual counts were made. The advantage of the dry-weight method in reducing error is clearly shown in the followmg comparisons: Method Percentage error Investigator Mean Range 0.3 6.7 5.1 0. 1 to 2. 2 0.4 to 21.0 3.0 to 14.0 Wet weight-- Volumetric Brown and Moflett (1942). Stone (1938). The number of eggs per fish in the Green Ba3'^ lake herring (table 39; fig. 12) varied widely but nevertheless exhibited a tendency to increase with length of the fish. In the entire sample of 72 fish with an average length of 11.2 inches, the average number of eggs was 6,375. Fish of different age but of the same length showed no diff'erence in egg 10 I I TOTAL LENGTH Figure 12. — Relation between length of Green Bay lake herring and number of eggs. The dots represent indi- vidual fish and circles are averages for 0.3-inch length groups; the line was fitted by least squares to the means of the 0.3-inch groups. number (details of analysis are not presented here). The relative number of eggs (expressed as number of eggs per ounce of body weight), contrary to the actual number, showed a downward trend with increase in length (fig. 13). For the entire sample (61 fish — 11 fish not weighed) the average number of eggs per ounce of fish was 1,012 (table 39). This value is below those for the ciscoes of Swains TOTAL LENGTH (INCHES) Figure 13. — Relation between length of Green Bay lake herring and the number of eggs per ounce of body weight. The dots represent individual fish and circles are aver- ages for 0.3-inch length groups; the hne was fitted by least squares to the means of the 0.3-inch groups. LAKE HERRING OF GREEN BAY, LAKE MICHIGAN 125 Lake (1,103 eggs per ounce of fish). Lake Erie (1,546 eggs per ounce of age group II fish), and Irondequoit Bay (1,369 eggs per ounce of fish) as computed from data given by Brown and Moffett (1942), Scott (1951), and Stone (1938), respec- tively. Table 39. — Relation between the length of the individual lake herring and the number, weight, and size of the eggs it produces (Number of fish In parentheses] Total length (Inches) Number of eggs per fish Num- ber of eggs per ounce of flshi Average egg diameter (millimeters) Aver- age Range Octo- ber Novem- ber 8 5 to 8 7 3,748 (1) 5.985 (4) 5,182 (2) 6,662 (15) 6,079 (16) 5,790 (14) 6.140 (U) 7,663 (4) 8,109 (1) 8,368 (2) 8,061 (1) 5.304 (1) 1,102 (1) 1,202 (4) 1,027 (1) 1,156 (16) 976 (16) 918 (11) 851 (9) 986 (3) 977 (1) 1.61 (1) 1.55 (2) 1.68 (1) 1.59 (12) 1.63 (11) 1.65 (10) 1.64 (3) lOOtolO.2 4,419 to 7,641 5,025 to 6,339 3,968 to 11,212 3,471 to 9,102 3,783 to 9,924 4,602 to 8,120 5,085 to 10,250 1.86 10.3 to 10.5 (2) 1.99 10.6 to 10.8 - (1) 1.75 10.9 to 11.1 - (3) 1.95 11 2 to 11.4 (4) 1.91 11.5 to 11.7 (3) 1.94 11.8 to 12.0 - (1) 1.75 12 1 to 12 3 (1) 1 87 12 7 to 12.9 6,294 to 10,442 (1) 1.87 13 to 13 2 (2) 1.98 13 6 to 13 8 (1) 1 98 (1) AU lengths 6,375 (72) 3,471 to 11,212 1,012 (61) 1.62 (52) 1.88 (20) I Records of weight were lacking for 11 flsh. The average egg diameters showed no tendency to change with increase of length but were larger in fish of the spa^vning run in November (1.88 mm.) than in the prespawning October specimens (1.62 mm.). Other analyses revealed no correla- tion between egg diameter and total number of eggs in individual fish. SPAWNING Time and factors of spawning According to available records, lake herring in the latitude of the Great Lakes spawn sometime between mid-November and mid-December, and spawning activity at one location usually covers a period of 1 to 2 weeks. That the spawning date may differ with latitude is indicated by Dymond (1933), who found evidence that the lake herring of Hudson and James Bays spawn as early as September 10. Water temperature unquestion- ably is an important factor influencing the time of 388748 O 57 6 spawning. Cahn (1927) stated that ciscoes did not begin to spawn in Lakes Mendota and Oco- nomowoc, Wisconsin, until water temperature had dropped below 4° C, and that the temperature was either 3.1° or 3.0° C. at the time spawning ended (5 years of observations). To verify this apparent relation between temperature and spawn- ing, Cahn (p. 100) held 25 ciscoes in tanks with the following results: * * * The water was kept at a temperature of 4.5° C. during a period of four months [weeks?], covering the breeding season. In spite of the fact that fifteen of the confined fish were females, all heavy with eggs, not a single egg was laid during this time. In a second tank, exactly similar to the first, and with the same water sup- ply, but cooled by means of ice to a temperature of 3.5° C, females from the first tank spawned within ten minutes after transfer. \ second experiment consisted in transferring two females into the second tank while the water was 4.5° C. After two hours in this tank, a large piece of ice was added and a careful record of the temperature kept. The first female spawned with the temperature at 3.6° C, the second at 3.4° C. Monti (1929) found that whitefish did not spawn in Italian lakes where winter temperatures remained above 7° or 8° C. Evidence supporting the hypothesis of a critical breeding temperature was given by Pritchard (1930). During the spawn- ing period of the lake herring, which starts in raid- November, the temperatures at a hatchery intake near Belleville in the Bay of Quinte, Lake Ontario, were — Date Temper- ature (°C.) Date Temper- ature (°C.) Nov. 15 6.1 7.8 6.1 4.4 Nov. 23 - 4.4 16. 24. 3.3 17 25 3.3 18 Stone (1938) recorded a temperature of 3.8° C. shortly before ciscoes started to spawn in Ironde- quoit Bay, Lake Ontario. He observed also that spawning started earlier in the southern end of the bay where water temperatures dropped sooner than in the northern end. Washburn ' reported water temperatures near 3.3° C. during cisco spawning in Birch Lake, Michigan. Brown and MofFett (1942) found spawning at its peak in Swains Lake, Mich., on December 14, 1937, when • Washbrnn, Oeorge N. 1944. Experimental gill netting In HIrch Lake, Cass County, Michigan, Michigan Department of Conservation, Institute tor Fisheries Research, Rept. No. 948, 33 pp. (Typewritten.] 126 FISHERY BtJLLETIN OF THE FISH AND WILDLIFE SERVICE the surface-water temperature was "* * * prac- tically at the freezing point." They expressed the belief that spawning may have continued for several days after ice covered the lake. Although the lake herring of Green Bay spawns from mid-November to mid-December, considera- able variation in the progress of spawning activi- ties does take place. It is believed, however, that some spawning is going on every year some place in the bay during this entire period. An example of the dynamic situation during the progress of spawning in Green Bay is offered by records of catches of a single pound net at Sister Bay in December 1950. On December 2 the catch consisted mostly of ripe fish ready to spawn; on December 3 about 50 percent of the fish were spent; on December 4 all of the 112 lake herrmg examined from the catch of this net were spent; furthermore, their gonads were in an advanced state of recovery — a condition typical of that found in February. This observation suggests that (1) Lake herring move in schools during the spawning period in Green Bay; (2) fish of one school do not necessarily complete spawning in the place at which they have started; and (.3) schools in one area do not all spawn at the same time. Differences in progress of spawning between various groups of fish most probably are the re- sult of differences in the temperature regime in the several parts of this hydrographically complex bay (see General Features of Green Bay, p. 88). Available temperature records are inadequate for study of local differences during the spawning season. Records that have been made, however, show that the temperature drops through the 4° to 3° C. range during the last half of November and the first half of December when spawning takes place. Spawning grounds Most reports, particularly those concerning in- land lakes, indicate that eggs of lake herring are laid in shoal areas 3 to 10 feet deep (Bean 1902; Cahn 1927; Pritchard 1930; Stone 1938). Al- though no evidence was given that spawning did not occur in deeper water, the regularly observed movement of fish into shoal areas and back to deep water clearly indicates that the shallower region must be the preferred spawning area. Wagner (1911, p. 76) reported that in Green Lake, Wisconsin, which is 237 feet deep, "Local fishermen generally believe that spawning takes place at a depth of about seventy feet, on marly bottom, but this is somewhat doubtful." Koelz (1929) related that lake herring spawn in water 60 feet deep at the western end of Lake Erie and in water 30 to 150 feet deep at the eastern end. In Lake Ontario, Koelz said a deep-water form spawns in 90 to 180 feet whereas shallow-water lake herring spawn in 60 feet of water. In Green Bay, spawning fish are most concentrated in water 10 to 60 feet deep but catches of both ripe and spent fish are observed from nets fished at depths down to at least 140 feet. Apparently, spawning takes place over practically all depths and in all sections of the bay. Spawning lake herring in general show no pref- erence for a particular bottom type. Spawning has been reported over boulders, gravel, sand, marl, clay, mud, and aquatic vegetation. In Green Bay, spawning takes place over areas of boulders, sand, and mud, with no clear indication of preference. The failure to select particular bottom types probably stems from the fact that lake herring are pelagic spawners. Evidence that eggs are extruded a considerable distance above the bottom is given by Pritchard (1930), who found eggs evenly scattered over the bottom with no evidence of local concentrations that would be expected if eggs were deposited near the bottom. Spawning behavior Few observations have been made of the spawn- ing act of lake herring. Cahn (1927) described spawning activity of ciscoes in Lake Oconomowoc as being slow and deliberate with no chasing or darting about. In contrast with Cahn's observa- tion, Bean (1902) described the night-time spawn- ing activity of the tullibee in New York as being accompanied by "* * * constant loud splashing and fluttering." This type of activity has also been reported by Washburn (see footnote 9, p. 125) in Birch Lake, Michigan, where "The fish were seen darting about singly and in pairs, oc- casionally coming to the surface and splashing the water. The appearance of these fish on shoals would take place just before dark at or about sunset and continue until 10:00 p. m." Fishermen of Green Bay tell of similar jumping and splashing activity of lake herring during the spawning pe- riod. No observations have been reported on LAKE HERRING OF GREEN BAY, LAKE MICHIGAN 127 the part this activity plays in the spawning process. Brown and MofTett (1942, p. 149) ob- served ciscoes breaking water in vSwains Lake in the early evening during the peak of the spawning period and remarked, "There was no concentra- tion of these fish. Approximately as many were seen over deep water as were observed over the shallows." The greatest depth of Swains Lake is 64 feet. Progress of spawning by age, sex, and size Although the lake herring population of Green Bay, taken as a whole, may show irregular prog- ress of spawning, there seems to be some pattern in the progress of spawning of individual segments of the population. The data of the only two samples that contained a good representation of both ripe and spent fish (table 40) show that, without excep- tion, the longer fish tended to spawn before the shorter fish and that the percentage of spent males was greater than that of females. In both sexes the upward trend in the percentage of spent fish with increase of age suggests that older fish spawn earlier than do younger fish. Table 40. — Comparison of ripe and spent lake herring in spawning-run collections from Green Bay, by sex and age group, November 2^30, 1950 [Length in inches] Ripe Spent Age group Number offish Total length (Inches) Number offish Total length (inches) Percent- age spent Males: I 1 2 29 8 9.7 10.8 10.8 11.1 II 2 45 12 2 11.1 11.1 11.2 11.8 50 Ill IV V Females: II 2 38 14 10.7 10.8 U.O Ill , IV : 38 18 11.4 11.9 50 56 Predation on eggs Possibly the greatest mortality in the life cycle of lake herring takes place immediately after the eggs are laid. A common predator on these eggs is the lake herring itself. Stone (1938) found cisco eggs in 23 of 34 cisco stomachs collected during the spawning season. Pritchard (1931) found cisco eggs in 6 of 46 cisco stomachs. In Green Bay, 16 stomachs of 19 feeding lake herring taken on November 28, 1950, contained from 1 to 33 herring eggs. Although the lake herring com- monly eats its own eggs, other species seem to to make greater inroads. Stone found from a few to 200 cisco eggs in stomachs of 20 of 36 brown bullhead (Ameiurus nebiUosus) and believed this fish to be an important predator in Irondequoit Bay. Pritchard noted cisco eggs in the brown bullhead in Lake Ontario, but the yellow perch was a heavier consumer of cisco eggs (average of 275 eggs per stomach) during the peak of spawn- ing. He also found cisco eggs in whitefish stom- achs, but the numbers were small as whitefish were not present during the main spawning period. Rawson (1930) also reported that whitefish feed on cisco eggs. Jordan and Evermann (1902) found that the mud-puppy (Necturus maculosus) con- sumes cisco eggs in Lake Erie. These reports of predation on cisco eggs have been mostly inci- dental and have not been based on a special study of this problem. Since lake herring eggs, after being laid, lie unprotected on the bottom, varia- tion in the amount of predation at this stage may influence the relative strength of a year class. DISTRIBUTION AND MOVEMENTS The distribution of lake herring during the summer months has been a subject of much com- ment in the literature (Cahn 1927; Fry 1937: Hile 1936; Hile and Juday, 1941; Koelz 1929; Nelson and Hasler, 1942; Pearse 1921; Reighard 1915; Scott 1931 ; Stone 1938; Van Oosten 1930; Wagner 1911). Although the observations of various authors are not exactly comparable because char- acteristics of the bodies of water studied were different, the distribution is similar in all lakes of the same type. Upon the warming of surface waters in the spring the lake herring, a steno- thermic, cold-water animal, avoids this change by vacating shallow water. As warming continues and a thermocline develops, undesirable or intol- erable temperatures of the epilimnion may cause the lake herring to be restricted to the thermocline and hypolimnion. In the southern portion of their range lake her- ring are rarely found in lakes that do not develop thermoclines or where the hypolimnion becomes unusually warm. In Indian Village Lake, Indiana, near the extreme southern limit of the range, they have adapted themselves to conditions that might be considered intolerable elsewhere (Scott 1931). In lakes in which either the oxygen becomes depleted or undesirable gases are formed in the 128 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE hypolimnion, lake herring are forced to inhabit the area of the thermocline. In years of such extreme stagnation lake herring must choose be- tween the epUimnion with adequate oxygen and unsuitable temperatures, or the hypolimnion with inadequate oxygen and suitable temperatures. Cahn (1927) reported that in situations of this type heavy mortalities occur in southern Wiscon- sin lakes. During a period of extreme stagnation in Snow Lake, Indiana, Scott observed ciscoes coming to the surface, apparently in a state of asphyxiation. These fish recovered quickly, how- ever, and returned to deeper water. According to Koelz (1929) the lake herring of Lakes Erie and Huron follow the normal pattern by descend- ing into deep water during the midsummer months. Koelz reported that lake herring were taken in Lake Superior 1 mOe off Grand Marais, Minn., in floating gill nets all year except late July and early August. Surface temperatures in this region are always relatively low. Among the authors who have reported on the vertical distribution of the lake herring, only a few have given limnological records or experi- mental data from which judgment can be formed as to limiting values of the controlling factors. Most detailed consideration of the problem was given by Hile (1936) and Fry (1937). From Hile's data on the vertical distribution of ciscoes and on temperature and oxygen conditions during the general period of his fishing operations (he had no limnological records on the actual dates of lifting gill nets) in Muskellunge and Silver Lakes, it may be seen that ciscoes were taken only rarely at temperatures above 17° to 18° C, which marked the upper limit of their distribution, or at oxygen concentrations below 3 or 4 parts per million at the deeper limit of their distribution. Fry com- mented that he seldom took ciscoes in Lake Nipissing in water 20° C. or warmer. He men- tioned oxygen depletion as a possible limiting factor for the lower limit of distribution, but con- sidered carbon dioxide concentration to be of greater importance in making the hypolimnion uninhabitable. Hile did not mention carbon diox- ide as a factor in the distribution of the cisco, but in a later publication on the bathymetric distribu- tion of fish in several lakes of northeastern Wiscon- sin (Hile and Juday, 1941) skepticism was ex- pressed as to the influence of both carbon dioxide and pH concentrations on the distribution of various species in those waters. Cahn's (1927) aquarium experiments indicated that ciscoes avoided temperatures above 17° C. Of the several possible limiting factors men- tioned by earlier investigators only temperature can be held important in Green Bay. Oxygen concentrations in the deeper waters of the bay during the summer of 1952 were always above 7 p. p. m. and the pH fell within the range 7.8 to 8.2. Although determinations were not made of carbon dioxide concentrations in deep water during the summer, the values for oxygen and pH constitute prima-facie evidence that carbon di- oxide was not present in excessive amounts. VERTICAL DISTRIBUTION IN GREEN BAY The occurrence of lake herring in commercial nets in Green Bay gives some information about the vertical distribution of the herring. In months of cool weather (September or October to May or June) lake herring are commonly taken in pound nets fished in shallow areas and in gill nets fished at all depths. During other months, how- ever, nets set in shallow water make only oc- casional catches, usually following a storm, and gill nets fished on the bottom in deeper water take few lake herring. In 1952, a study was undertaken to determine the distribution of the lake herring before, during, and after the summer period when, according to the fishermen, the lake herring "disappear." Oblique gUl-net sets,'" similar to those used by Fry (1937), were employed to determine the depth at which lake herring were located. In these sets 140 linear feet of gill netting were fished in every 15-foot stratum. At station B, where the water was 40 feet deep, 140 feet of gill netting were fished in each 20-foot stratum. One end of the gang of nets was tied to an anchor and the other end to a 15-gallon-drum float. The depths at which segments of the nets fished were con- trolled by gallon-jug floats attached to the nets with lines whose lengths were multiples of 15 feet. To hold the nets tight, an anchor rope about equal in length to the gang was tied to the 15-gallon drum, puUed against the first anchor, and set with a long buoy line (see figure 14 for a diagram of an oblique set in 60 feet of water). " These experimental nylon gill-nets were 280 feet long and 6 feet deep, and had mesh sizes of 1, H, and 2 inches, eitension measure. The 2-inch-mesh nets were used most eitensively. i LAKE HERRING OF GREEN BAY, LAKE MICHIGAN Table 41. — Vertical distribution of lake herring taken in oblique sets of gill nets in different periods [Mesb slies, extension measure, In Inches] 129 Month, station, and depth date set and lifted Mesh size Number of fish Percentage of catch at— 0-15 feet 15-30 feet 30-45 feet 45-60 feet 60-76 feet 75-90 feet EARLY mat: A (30ft.) 3-4 3- 4 3- 4 1-2 8-9 8- 9 8- 9 10-11 10-11 10-11 5- 6 5- 6 6- 7 7-8 7- 8 24-25 24-25 24-25 21-22 21-22 21-22 10-1 1 11-12 11-12 23-24 23-24 27-27 21-22 21-22 19-21 19-21 19-21 21-22 21-22 21-22 22-23 23-24 23-24 24-25 24-25 24-25 IVi IM IM 1 J^ 2 2 2 IH Hi 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 1 80 5 7 45 26 115 118 28 13 32 5 85 31 31 82 18 46 19 6 10 24 152 90 197 15 46 379 19 189 439 1,220 645 446 100 1 42 9 65 30 70 7 85 94 60 60 87 87 17 1 1 100 96 45 58 52 29 14 34 11 2 4 23 7 12 7 15 6 40 34 10 13 1 6 9 5 1 3 13 4 37 42 33 36 21 36 52 B (40ft. )i C (60 (t.) 11 20 45 12 11 10 14 29 20 29 33 28 8 11 D(90ft) 39 40 29 7 18 Do 20 Do Do --.. 2 E (60 ft ) F(90ft) 19 5 O(60ft.) H (60 ft ) I (90ft.) 21 40 J (90 ft ) K (60 ft ) L(60ft.) - LATE MAY. A (30ft.) - B (40 ft.)' - C(60ft) 4 14 33 37 2 39 44 54 E (60 ft.) - 3 Q(60ft.) J (90ft.) 28 18 L(60ft) A (30 ft.) 42 17 40 21 7 78 S3 53 60 63 12 18 34 D (90 ft.) 17 66 H(60ft.) - I (90 ft.) 8 14 8 J (90 ft.) 65 K (60ft.)._ OCTOBER: A (30 ft.).- - B (40ft.)i C (60 ft.) 11 9 19 28 23 21 7 6 13 26 7 16 D(90ft.) H (60ft.)._. I (90 ft.) 2 9 1 J (90 ft.) - 2 K (60 ft.) L(60ft.) Depth Intervals 0-20 and 20-40, one 280-foot net used from surface to bottom. i^si^^sgMgg;ss^i:^sg::^^?gj;^^^^t^^i^^^^j^!j^^ Figure 14. — Method of setting a gill net in an oblique position. Horizontal scale much reduced. It was obviously impossible to avoid some sagging in the gang. The amount of sag was lessened by the action of currents which are almost always fairly strong in Green Bay. Oblique sets of gill nets were fished at 12 stations in representative areas throughout Green Bay (fig. 1) from early May to late October 1952. One station (A) was established in 30 feet of water and another (B) in 40 feet in the shallow southern portion of the bay. Six stations (C, E, G, H, K, L) were located in 60 feet of water, and 4 stations (D, F, I, J) in 90 feet. No lake herring were taken at the shallow- water station A (30 feet) in southern Green Bay and only one was caught at station B (40 feet) in early May (table 41); only a few were taken in late May (A, 13 fish; B, 32 fish) at which time they were found mostly in the upper 15 to 20 feet of water. No lake herring were obtained at the 30-foot station in July. A few were again taken at both stations in October (A, 15 fish; B, 46 fish) when lake herring were concentrated near the surface. Since the distribution of fish varied randomly among individual 60- and 90-foot stations in southern, central, and northern Green Bay during any one season, data for stations of equal depth have been combined to show seasonal differences in distribution. The graphical representations of distribution of lake herring at 60-foot stations 130 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE OCTOBER 21 -2S Figure 15.— Vertical distribution of lake herring taken in oblique sets of gill nets in 60 feet of water. The full width of the panel for each time period is 100 percent. OCTOBER 22-25 Figure 16. — Vertical distribution of lake herring taken in oblique sets of gill nets in 90 feet of water. The full width of the panel for each time period is 100 percent. (fig. 15) and at 90-foot stations (fig. 16) are given as unweighted mean percentages for all stations where lake herring were caught. Despite the concentration of lake herring in the upper 15-foot stratum at 60-foot stations (E and G) in early May (67.9 percent, fig. 15), evidence at 90-foot stations where nets were fished on the same and other dates in early May (table 41, fig. 16) suggests a possibly random distribution. In late May the lake herring were concentrated in the top 15-foot stratum at both 60- and 90-foot stations (69.0 and 87.1 percent); most of the remaining fish were at the 15- to 30-foot level (29.0 percent at 60-foot stations and 9.7 percent at 90-foot stations). Lake herring exhibited a strong tendency to move into water deeper than 30 feet in June (84.5 percent at 60-foot stations and 98.7 percent at the 90-foot station); the tendency toward concentration below 30 feet was still greater in July (94.4 and 99.3 percent at 60- and 90-foot stations). Lake herring were present in fair numbers except in deepest water (75 to 90 feet) in October but showed a decided tendency to be concentrated in the upper 30 feet (74.6 and 66.8 percent at 60- and 90-foot stations). The general seasonal trend in vertical distribu- tions from May to October may be summarized as follows. The first change was from a variable pattern in early May to a pelagic distribution in late May. In June and July the lake herring had descended to depths greater than 30 feet and by October they had resumed the pelagic habitat with the greatest concentration between the surface and 30 feet. The distribution of lake herring during the spawning period in November and December has been brought out in the discussion of spawning activity. Distribution during winter and early spring is subject of much speculation. The few observations that have been made lead to the conclusion that schools of lake herring may be found at any depth. The vertical distribution of lake herring showed no relation to temperature, except in the avoid- ance of water with temperature near or above 20° C. In early May when the water was rela- tively cool (3.2° to 7.6° C. at stations where lake herring were caught) and varied little with depth (table 42), the distribution of herring was largely random (table 41). Late May temperatures are available for only the shallow-water stations (A and B); the surface temperatures at these loca- tions were 14.1° and 14.5° C. and bottom tem- peratures were 13.0° and 11.6° V. Although the lake herring had moved toward greater depths in June, it cannot be assumed that increasing water temperature near the surface was the cause. The temperatures from the surface to 30 feet were between 12.3° and 15.1° C. (total range at all stations) — not greatly different from those at stations A and B in late May. The lake herring continued to be concentrated below 30 feet in July. During this month water tempera- tures at less than 30 feet (fig. 17 and table 42) usually were within the range of 18.3° to 21.5° C. (the range from 15.6° at 20 feet to 18.6° at the surface on July 24 represents a transitory situation following a severe storm). Since these July tem- peratures from the surface to 30 feet were mostly near or above the values considered critical for the lake herring (see p. 128), it is probable that tem- perature conditions held the lake herring in greater depths in July. This view is supported by the absence of lake herring at shallow-water station A LAKE HERRING OF GREEN BAY, LAKE MICHIGAN 131 Table 42.— Water temperature at or near experimental gill-net stations [Temperature records made with a bathythermograpb. Depth of cast (feet) is Indicated by deepest temperature recorded] Period and station ' Day of month Temperature (° C.) at depth of— Ofeet 10 feet 20 feet 30 feet 40 feet SO feet 60 feet 70 feet 80 feet 90 feet 100 feet E*RLY may: A - - 3 3 1 8 10 11 11 10 11 5 6 7 7 24 24 10 11 11 11 23 24 24 23 24 22 27 21 21 22 19 21 19 21 19 21 21 21 21 22 22 23 23 23 24 24 24 24 12.1 13.1 3.2 9.2 6.6 6.0 6.9 7.6 7.5 5.5 7.S 8.6 6.0 14.1 14.5 12.9 13.1 13.6 15.1 20.5 19.8 19.6 19.9 18.6 20.2 20.6 20.3 21.3 21.5 20.5 21.4 20.3 20.2 20.7 20.5 8.4 8 9 9.2 9.4 9.9 9.8 10 2 10 1 10 9.5 9.7 8.5 9.1 8.4 3.2 8.0 6.6 6.0 5.9 7.0 7.1 S.4 7.5 8.2 6.0 13.8 13.6 12.9 13.1 13.5 15.0 20.5 19.8 19.3 19.9 16.9 20.1 20.5 20.2 21.1 21.5 19.9 21.2 19.7 19.9 19 4 20.4 8.4 8.9 9.2 9.4 9.9 9.8 10.2 10.1 10.0 9.5 9.6 8.3 8.6 7.4 3.2 6.9 6.5 6 5.6 6.6 6.9 5.1 7.4 8.0 5.3 13.1 13.5 12 8 12.5 13.0 14.4 20.5 19.7 18.3 19 6 15.6 19.9 20.2 19.9 21.0 21.2 19 2 19.7 19.1 19.5 18.7 19.9 8.4 8.9 9.2 9.4 9.9 9.8 10 2 10.1 10.0 9.4 9.4 8.3 B - 6.9 3.2 6.6 6.5 6.0 5.5 5.9 6.8 4.5 7.3 7.6 5.2 13.0 13.3 12.8 12.3 12.6 13.7 20.3 19.7 11.4 18.5 14.7 11.5 20.0 11.7 20.4 19.5 18.5 18.5 19.0 18.6 15.6 14.5 8.4 8.9 9.2 9.4 9.9 9.7 10.2 10.0 10 9.3 9.4 8.2 D 3.2 6.2 6.5 6.0 5.2 4.9 6.6 4.2 7.2 6.6 5.2 3 2 5.8 3.2 .<> 4 3.2 5.3 5.9 6.0 4.3 3.2 5.2 3.2 5.1 D SO E 6. 5 6 3 E 6.0 4.8 4.8 6.1 4.2 7.1 6.1 5.2 6.0 4.3 4.7 5.3 4.2 7.0 S.3 5.2 F 4.3 4.3 I 4.2 6.9 4.2 5.1 4.2 SO 4.2 J 5.0 K L LATE MAV: A - B 11.6 12.6 11.6 11.5 11.2 JUNE: J 12 2 10.8 9.3 7.3 11.1 9.1 7.7 6.2 8.4 7.5 6.0 7.6 6.0 7.3 K - K L ji'LT: A A B 10.2 12.0 14.2 9.8 17.7 9.2 18.0 14.6 13.9 14.5 17.0 14.5 14.0 12.1 C .... 9.6 13.0 8.8 10.0 8.9 12.6 10.1 10 6 12.9 11.0 10 4 11.5 10 9.0 9.6 7.9 8.1 8.4 8.5 8.4 9.9 11 5 10.2 9.6 9.6 9.1 7.8 7.5 8.4 7.9 7.2 8.9 10 1 10.1 9.4 9.0 8.7 7.6 7.4 C D 7.S 7.3 7 2 H 7.2 6.8 8.3 10.0 6.9 6.8 8.0 9.0 6.8 I 8.7 J 8.0 J. 8.7 K K L L 9.1 OCTOBER: A B... 8.9 9.2 9.4 9.8 9.7 10.1 10 10 9.3 9.4 8.1 C 9.2 9.4 9.7 9.7 10.1 10.0 10.0 9.3 9.4 8.1 9.2 9.4 9.7 9.6 10.0 10.0 10.0 9.3 9.4 8.1 c D ._ 9.6 9.5 10.0 10.0 9.9 9.3 9.4 9.5 9.3 9.5 B.S D H- I... 10.0 9.8 9.3 10.0 9.8 9.3 10.0 1- . J K 9.3 L . I See figure 1 for location. where the temperatures on July 23 and 24 were 19.7° to 20.5° C. In October when the lake herring were again most plentiful from the surface to 30 feet, the water temperature was generally cool (8.1° to 10.2° C.) and the temperature gradi- ents from top to bottom were insignificant (great- est difference 0.4°). The one previous study of the vertical distribu- tion of the lake herring in relation to size of fish was made by Fry (1937) in I^ake Nipissing. Fry found that the movement from shallow water to the hypolimnion was not a mass descent but was "* * * an orderly succession of certain groups of individuals which migrate in order of size and sex." Consideration of the distribution in rela- tion to sex was made earlier (p. 120) in the dis- cussion of sex composition. In the summary o the length of lake herring taken at various depths (table 43) the sexes are combined, as no sex differ- ences in length were found for fish taken in the same depth of water. Despite certain exceptions (usually at depths in which the catches were small) the average size of lake herring tended to decrease with increase in depth of water in all collecting periods. Davidoff " found a similar tendency for the larger ciscoes of Myors Lake, Indiana, to be near the surface. The seasonal changes in the distribution of the lake herring must be a major cause of the highly " Davidofl, Edwin B. 1953. Growth, response to netting, and bathy- metric distribution of the Cisco. Levcichthysarledii (Le Sueur) In Myers Lake. Indiana. M. S. thesis. Department of Fisheries. University of Michigan. (Typewritten.) 132 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE D H I J K J I L 10 IS 20 TEMPERATURE (°c) 10 IS 20 10 15 20 15 20 25 Figure 17. — Relation between temperature and vertical distribution of lake herring July 19-27, 1952. See figure 1 for locations of stations. The full width of the panel for each station represents 100 percent. Table 43. — Length of lake herring taken in oblique sets of gill nets, by depth and season, 1952 12-inch-mesh gill nets, all stations combined. Length in inches] May 1-11 May 21-25 June 10-12 July 19-27 October 21-26 Depth (feet) Number offish Total length Number offish Total length Number offish Total length Number offish Total length Number offish Total length n to 15 137 30 48 66 26 7 11.0 11.0 10 9 10.9 10.8 10.7 119 40 3 2 11.1 10.9 10.9 10.5 4 6 34 65 23 15 11.1 10.5 10.8 10 9 10.8 10.7 2 31 87 95 24 33 11.1 11.0 10.7 10.6 10.7 10.7 279 210 206 212 38 33 11.3 15 to 30— 11.2 30 to 45-- 11.0 46 to 60 10.8 60 to 75 11.1 76to90- 1 10.7 10.7 seasonal character of the fishery. Nearly half (47.2 percent) of the commercial catch is made during the fourth quarter of the year (fall) and a fourth (24.4 percent) during the first quarter (winter). (See table 2.) Production is much lower in the spring (19.5 percent) and summer quarters (8.9 percent). Principal gear for taking lake herring are pound nets which fish from the surface to the bottom and are seldom set at depths greater than 35 to 40 feet, and gill nets which are set on the bottom at all depths but are effective only 6 to 1 1 feet above the bottom.'^ Thus, pound nets can take herring only when the fish are in the shallower inshore waters and gill nets can capture them only when the fish are near the bottom. From figures 15 and 16 it may be seen that in June and July " In State of Michigan waters gill nets may not be more than 11 feet deep (distance from float line to lead line) ; In Wisconsin the greatest depth allowed (stated In numbers of meshes) is about 6 feet. most herring were in water too deep to be taken by pound nets. The same condition most probably held in August, September, and even early October. During the same period the lake herring should have been available to gill nets set in deeper water. Examination of the nets as they were lifted from oblique sets revealed, however, that most of the herring taken in the bottom 15- foot stratum were caught in the upper half of the net section. Because the fish are some 6 to 8 feet above the bottom, commercial fishing with gill nets during the summer period is not productive. The distribution pattern in which some, and at times most, lake herring are above the bottom and out- side the 30- to 40-foot contour provides them a considerable degree of protection from commercial exploitation. In view of the relative inefficiency of present fishing gear, the probability of depletion by the present fishery is small. LAKE HERRING OF GREEN BAY, LAKE MICHIGAN 133 MOVEMENTS AND ACTIVITY Available evidence shows that the lake herring, as well as other coregonids in the Great Lakes, does not undergo extensive migrations. Principal source of information is the study of Smith and Van Oosten (1940), who reported the following percentage recaptures from Lake Michigan fish tagged from 1929 to 1931 near Port Washington, Wis.: 5.4 percent from 593 lake herring; 22.1 percent from 457 whitefish; 5.7 percent from 106 chubs {Leucichthys spp., other than lake herring); and 20.0 percent from 35 pilots, or round white- fish {Prosopium cylindraceum quadril late rale). Lake herring were not recovered at distances greater than 50 miles from point of tagging, while lake trout and rainbow trout tagged in the same study were recaptured at distances as great as 125 to 225 miles away. The percentage distribution of recoveries was as follows: Miles traveled from point of release Lake herring Whitefish Chubs Pilots 1 to 10 69 28 3 67 29 I 3 100 100 11 to 25 26 to 50 51 to 75 Jarvi's (1920) study of the "kleine Marane," a species similar to the lake herring, in Keitelesee, Finland," disclosed the presence of distinct stocks, with respect to growth and age composition, in different basins. In view of these differences he concluded that the movements of the "kleine Marane" must be limited and that the few ob- served migrations probably resulted from unusual temporary conditions. Local movements of the lake herring that have been observed probably are the result of thermal conditions or represent spawning and feeding ac- tivities. The vertical movement accompanying thermal stratification is not as great as the hori- zontal distances that must be traveled in Green Bay when the fish abandon the .warming shallow- water areas to seek colder water. This distance amounts to about 10 miles in northern Green Bay and 25 miles in southern Green Bay. Similar dis- tances are covered in the return to shallow-water areas prior to and accompanying spawning. In Lake Erie the summer and spawning movements, according to the distribution described by Van " The greatest length of Keitelesee Is 72 kilometers, or about 45 miles. Oosten (1930) must involve distances of 100 miles or more. Cahn (1927) found that theciscoes of Oconomo- woc Lake were closer to the surface at night than during the day, and he interpreted this diurnal mi- gration as a feeding movement. Jarvi (1920) ob- served the same diurnal movement in the "kleine Marane" of Keitelesee. He believed that the local horizontal movements of schools of "kleine Ma- rane," as well as the diurnal movements, were asso- ciated with feeding. Similar movements of lake herring schools in Green Bay are shown by the highly erratic catches of nets fished in the same locality day after day. A good example is found in the catches at Sister Bay on December 2, 3, and 4, 1950, where a pound net apparently took members of three different schools on three suc- cessive days (see p. 126). There is some evidence that the strong currents, which are common in Green Bay, are responsible for movement of lake herring. These movements are reported by commercial fishermen who occa- sionally, following summer storms, take lake her- ring in shallow-water areas where they are not normally found during the summer period. These occurrences indicate that lake herring can be trans- ported by currents. SUMMARY 1 . The lake herring occurs in many of the deeper, colder lakes of the northeastern section of the United States, over most of Canada and Alaska, and also in Hudson and James Bays. It is rarely found in rivers. 2. Green Bay is one of the most productive com- mercial fishing areas in the Great Lakes and the lake herring is a major contributor to the total catch in the bay. In 1952 Green Bay produced 38.7 percent of the total take of lake herring from all United States waters of the Great Lakes. The commercial catch fluctuates widely, but this study was conducted during years (1948-52) when production was high and relatively stable. 3. Green Bay is 118 miles long and 23 miles wide. Water exchange with Lake Michigan is rela- tively free in the northern end of the bay, but prac- tically nil in the southern section. Water move- ments in the bay are complex and often are of considerable magnitude. They result in an un- stable, almost continually changing environment within the bay. 134 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 4. Scales for studies of age, growth, and year- class strength were collected from 4,390 lake herring taken from pound and gill nets. Investi- gation of most phases of the life history was based on catches of pound nets, which are less selective with respect to size of fish than are gill nets. Length records were obtained for all and weight and sex data for most of the 2,039 lake herring taken from experimental gill nets. 5. Age determinations were made by examining the magnified image of scales projected on a screen. Fish with no annulus (year-mark) were assigned to age group 0, those with 1 annulus to age group I * * *. All fish were considered to pass into the next higher age group on January 1. 6. The maximum age of lake herring reported in any population is XII ; the oldest fish from Green Bay belonged to age group VII. The best-repre- sented age groups in the various populations for which there are published records are age groups II to V; age groups III and IV were the most plen- tiful in Green Bay. The commercial catch in Green Bay was dominated by age group IV in the period January to June and by age group III in July to December. 7. The age composition of lake herring from pound nets was not representative of the popula- tion, as young fish were seldom taken even though the mesh sizes (1)2 to 2 inches, extension measure) were small enough to hold them. Yearling lake herring, as a rule, do not inhabit the relatively shallow, inshore areas where pound nets are fished. 8. The length of lake herring from the commer- cial pound nets and gill nets varied little from season to season. Even during the summer period of rapid growth the effects of individual increases in length were largely compensated by the selec- tive destruction of the larger lake herring in the fishery and by the shift to a lower average age. 9. The relation between the total body length in inches (L) and the magnified (X41) scale diameter in millimeters (S) of Green Bay lake herring is described by the formula L = 0.01615 + 0.05486 S Since the intercept is so small, its value was assumed to be 0, and lengths at the end of various years of life were calculated from scale measure- ments by direct proportion. 10. Annuli are formed on scales of the Green Bay lake herring in May and June. The progress of annulus formation is irregular, possibly because of different local environmental influences. The younger age groups and the smaller fish within an age group tend to form annuli earliest. 11. Growth within the season was described by a sigmoid curve. Growth started about the first of May and terminated near the end of October, with the fastest growth in July. 12. Males and females grew at the same rate. 13. Selective destruction of fast-growing in- dividuals was so great that seasonal differences in style of growth were detectable, that is, lake herring taken early in the year had grown faster in earlier years than had fish of the same age group captured later in the same year. 14. Calculated length at the end of the first year of life increased from north to south. These first-year differences, almost surely of environ- mental origin, were rapidly reduced by com- pensatory growth in later years of life. 15. Annual fluctuations in growth in length indicated that conditions affecting growth of lake herring in Green Bay changed little from year to year. The growth rate was below average and decreasing from 1944 to 1946, improved from 1946 through 1950, and then declined somewhat in 1951. Growth was well above average during the period 1949-51. 16. The different age groups exhibited sys- tematic discrepancies in calculated growth re- sembling those commonly termed Lee's phenom- enon of "apparent decrease of growth rate." Selective destruction of the larger, faster-growing fish by the commercial fishery was held to be the most important of the various factors that may have contributed to the discrepancies. 17. Growth compensation takes place in Green Bay lake herring. It was shown that growth compensation will appear in the calculated growth of fish that follow identical growth curves but that are hatched at different times in the season. It was also demonstrated that length rather than age is the primary determinant of subsequent growth of the individual, and hence that growth compensation can occur among fish whose growth curves are different. 18. The general length-weight relation of the Green Bay lake herring is described by the equation log W^= -2.4386 + 3.0729 log L, LAKE HERRING OF GREEN BAY, LAKE MICHIGAN 135 where W is weight in ounces and L is total length in inches. 19. Weight varied according to sex and to method, season, and year of capture. 20. Females were relatively more abundant in samples taken from pound nets in February than in May to December. They were also more plentiful in the younger age groups than in the older. The selective destruction of females in younger age groups may be a major factor in the progressive decline with increased age in the percentage of females in a year class. 21. The percentage of females in the Green Bay lake herring population declined continuously from 1949 to 1952. 22. The percentage of females in collections taken in oblique sets of gill nets increased with depth of water in October. This change in sex composition with depth may reflect an actual difference in the distribution of the sexes, but a difference in the activity of the sexes may have been a major factor. 23. Some Green Bay lake herring matured during their second year of life, and all had reached maturity by the end of the third year. 24. Lake herring spawn in Green Bay between mid-November and mid-December, but spawning of an individual school of fish may be completed in a fraction of this period. Fish of the same school do not necessarily complete spawning in one location. Within a school, the older fish and the larger fish of an age group tended to spawn first and the males spawned earlier than the females. 25. Lake herring are pelagic spawners; the eggs are broadcast and settle unprotected to the bottom. Inshore areas are preferred, but there is evidence that lake herring may spawn in Green Bay over water as deep as 140 feet. 26. The literature indicates that lake herring hatch in early spring (April-May) and that newly hatched fry are pelagic. Young-of-the-year lake herring have rarely been collected. They prob- ably lead a bathypelagic existence where they are relatively immune from capture by the usual methods of collection. 27. Although the number of eggs produced by female lake herring (range, 3,471 to 11,212) varied widely for fish of the same total length as well as of different lengths, the number of eggs tended to increase with length of the fish. The relative number of eggs (i. e.. number per ounce of bodv weight) tended to decrease with increase of length. 28. The lake herring of Green Bay were ran- domly distributed from top to bottom in early May, but they were concentrated in the upper 15 to 30 feet in late May. They descended to deeper water in June and were restricted to strata more than 30 feet below the surface in July when tem- peratures in shallower water were unfavorable (17° C. and above). In October, lake herring were again found at all levels but were most abundant in the upper 30 feet. 29. Lake herring are not migratory but they sometimes move considerable distances to avoid unfavorable temperatures. Local movements are probably associated with feeding or represent passive transport by currents. 136 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE LITERATURE CITED Bajkov, Alexander. 1930. Fishing industry and fisheries investigations in the prairie provinces. Trans. American Fish- eries Soc, vol. 60, pp. 215-237. Bauch, Gerd. 1949. Untersuchiingen Uber das VVachstum der kleinen Marane (Coreqonus albula L.) in den Gewassern Mitteleuropas. Abhandlungen Fisch- erei, Deutschen Forschungsanstalt fiir Fischerei, Lieferung 2, S. 239-326. BEAINf, Tarleton H. 1902. Food and game fishes of New York. New York Forest, Fish, and Game Comm., Rept. No. 7, pp. 251-460. Brown, C. J. D., and J. W. Moffett. 1942. Observations on the number of eggs and feed- ing habits of the cisco (Leucichthys arledi) in Swains Lake, Jack.son County, Michigan. Co- peia 1942, No. 3, pp. 149-152. October 8. Butler, Robert L., and Lloyd L. Smith, Jr. 1953. A method for cellulose acetate impressions of fish scales with a measurement of its reliability. United States Department of the Interior, Fish and Wildlife Service, Progressive Fish-Culturist, vol. 15, No. 4, pp. 175-178. October. Cahn, Alvin Robert. 1927. An ecological study of southern Wisconsin fishes. Illinois Biological Monographs, vol. XI, No. 1, 151 pp. January. [Contributions from Zoological Lab. of the University of Illinois, No. 297.] Carlander, Kenneth D. 1945. Growth, length-weight relationship and popu- lation fluctuations of the tullibee, Leucichthys arledi tullibee (Richardson), with reference to the commercial fisheries, Lake of the Woods, Minne- sota. Trans. American Fisheries Soc, vol. 73 (1943), pp. 125-136. 1950. Handbook of freshwater fishery biology, v -f281 pp. Wm. C. Brown Co., Dubuque, Iowa. Clemens, Wilbert A. 1922. A study of the ciscoes of Lake Erie. Univer- sity of Toronto Studies, Biol. Ser., No. 20, Pub- lications Ontario Fisheries Research Lab., No. 2, pp. 27-37. Toronto. Cooper, Gerald P. 1937. Age, growth, and morphometry of the cisco, Leucichthys arledi (Le Sueur), in Blind Lake, Washtenaw County, Michigan. Papers Michi- gan Acad. Sciences, Arts, and Letters, vol. 22 (1936), Zoology, pp. 563-571. Ann Arbor, Mich. Dannevig, Alf, and Gunnar Dannevig. 1937. The season in which "winter" zone.s in the scales of trout from .southern Norway are formed. Jour, du Con.seil, Con.seil Permanent Inter- national pour L'E.xploration de la Mer, vol. 12, No. 2, pp. 192-198. Copenhague. Deason, Hilary J., and Ralph Hilb. 1947. Age and growth of the kiyi, Leucichthys kiyi Koelz, in Lake Michigan. Trans. American Fisheries Soc, vol. 74 (1944), pp. 88-142. Dymond, J. R. 1933. Biological and oceanographic conditions in Hudson Bay. 8. The coregonine fishes of Hud.son and James Bays. Biological Board of Canada, Contributions Canadian Biology and Fisheries, vol. 8, No. 1 (Ser. A, general. No. 28), pp. 1-12. Toronto. 1943. The coregonine fishes of northwestern Canada. Contributions Royal Ontario Museum Zoology, No. 24, pp. 171-232. 1947. A list of the freshwater fishes of Canada east of the Rocky Mountains. Royal Ontario Mu- seum Zoology, Misc. Publications No. 1, 36 pp. Toronto. Eddy, Samuel, and Kenneth D. Carlander. 1942. Growth rate studies of Minnesota fish. Min- nesota Department of Conservation, Division of Fish and Game, Bureau Fishery Research, In- vestigational Rept. No. 28, 64 pp. Farran, G. p. 1936. On the mesh of herring drift-nets in relation to the condition factor of the fish. Jour, du Con- seil, Conseil Permanent International pour L'Ex- ploration de la Mer, vol. 11, No. 1, pp. 43-52. Copenhague. Fish, Marie Poland. 1932. Contributions to the early life histories of sixty-two species of fishes from Lake Erie and its tributary waters. United States Bureau of Fisheries, vol. 47 (1935), Bull. No. 10 (1932), pp. 293-398. Ford, E. 1933. An account of the herring investigations con- ducted at Plymouth during the years from 1924 to 1933. Jour. Marine Biological Association of the United Kingdom, vol. 19, N. S., pp. 305-384. I'rey, David G. 1942. Studies on Wisconsin carp. 1. Influence of age, size, and sex on time of annulus formation by 1936 year class. Copeia 1942, No. 4, pp. 214-223. December 28. Fry, F. E. J. 1937. The summer migration of the cisco, Leucich- thys arledi (Le Sueur), in Lake Nipissing, On- tario. University of Toronto Studies, Biol. Ser., No. 44, Publications Ontario Fisheries Research Lab., No. 55, 91 pp. Toronto. Greeley, John R., and C. Willard Greene. 1931. A biological survey of the St. Lawrence water- shed. II. Fishes of the area. Supplement to 20th Annual Rept. for 1930, New York Conserva- tion Department, pp. 44-94. Hansen, Donald F. 1937. The date of annual ring formation in ths scales of the white crappie. Trans. American Fisheries Soc, vol. 66 (1936), pp. 227-236. LAKE HERRING OF GREEN BAY, LAKE MICHIGAN 137 HiLE, Ralph. 193]. The rate of growth of fishes of Indiana. In- vestigation of Indiana Lakes. II. Indiana De- partment of Conservation, Division of Fish and Game, Publ. No. 107, pp. 7-55. 1936. Age and growth of the eisco, Leucichthyx artedi (Le Sueur), in the lakes of the northeastern high- lands, Wisconsin. United States Bureau of FisherieF, vol. 48, Bull. No. 19, pp. 211-317. 1937. Morphometry of the cisco, Leucichthys artedi (Le Sueur), in the lakes of the northeastern high- lands, Wisconsin. Internationale Revue der gesamten Hydrobiologie und Hydrographie, Band 36, S. 57-130. 1941. Age and growth of the rock bass, Ambloplites rupeslris (Rafinesque), in Nebish Lake, Wiscon- sin. Trans. Wisconsin Acad. Sciences, Arts, and Letters, vol. 33, pp. 189-337. Madison. HiLE, Ralph, and Hilary J. Deason. 1947. Distribution, abundance, and spawning season and grounds of the kiyi, Leucichthys kiyi Koelz, in Lake Michigan. Trans. American Fisheries Soc, vol. 74 (1944), pp. 143-165. HiLE, Ralph, and Chancy Juday. 1941. Bathymetric distribution of fish in lakes of the northeastern highlands, Wisconsin. Trans. Wis- consin Acad. Sciences, Arts, and Letters, vol. 33, pp. 147-187. HiLE, Ralph, George F. Li'noer, and Howard J. Bt'ETTNER. 1953. Fluctuations in the fisheries of State of Michi- gan waters of Green Bay. United States Depart- ment of the Interior, Fish and Wildlife Service, vol. 54, Fishery Bull. 75, pp. 1-34. Hodgson, William C. 1924. Investigations into the age, length and matur- ity of the herring of the southern North Sea. Part I. Some observations on the scales and growth of the English herring. Ministry of Agriculture and Fisheries, Fishery Investigations, ser. II, vol. 7, No. 8, 36 pp. London. 1929. Investigations into the age, length and matur- ity of the herring of the southern North Sea. Part III. The composition of the catches from 1923 to 1928. Ministry of Agriculture and Fisheries, Fishery Investigations, ser. II, vol. 11, No. 7, 75 pp. London. Hi'BFs, Carl L., and Karl F. Lagler. 1949. Fishes of the Great Lakes region. Cranbrook Institute of Science, Bull. No. 26. xi+186 pp. Cranbrook Press, Bloomfield Hills, Mich. Jarvi, T. H. 1920. Die kleine Marane Coregonus albula L. im Keitelesee. Annales Academiae Scientiarum Fennicae, ser. A, vol. 14, No. 1, 302 pp. [Suomalai- sen Tiedeakatemian Kustantama.] Helsinki. Jobes, Frank W. 1943. The age, growth, and bathymetric distribution of Reighard's chub, Leucichthys reighardi Koelz, in Lake Michigan. Trans. American Fisheries Soc, vol. 72 (1942), pp. 108-135. Jobes, Frank W. — Continued 1949a. The age, growth, and distribution of the long- jaw Cisco, Leucichthys alpenae Koelz, in I.,ake Michigan. Trans. American Fisheries Soc, vol. 76 (1946), pp. 215-247. 1949b. The age, growth, and bathymetric distribu- tion of the bloater, Leucichthys hoyi (Gill), in Lake Michigan. Papers Michigan Acad. Sciences, Arts, and Letters, vol. 33 (1947), Part 2: Zoology, pp. 135-172. Jordan, David S., and Barton W. Evermann. 1902. American food and game fishes. 572 pp. Doubleday, Page, and Co., New York. Koelz, Walter. 1929. Coregonid fishes of the Great Lakes. Bull. United States Bureau of Fisheries, vol. 43 (1927), Part 2, Document No. 1048, pp. 297-643. 1931. The coregonid fishes of northeastern .America. Papers Michigan Acad. Sciences, Arts, and I^etters, vol. 13 (1930), pp. 303-432. Lee, Rosa M. 1920. A review of the methods of age and growth determination in fishes by means of scales. Ministry of Agriculture and Fisheries, Fishery Investigations, ser. II, Sea Fisheries, vol. 4, No. 2, 32 pp. London. McHuGH, J. L. 1941. Growth of the Rocky Mountain whitefish. Jour. Fisheries Research Board of Canada, vol. 5, No. 4, pp. 337-343. Moffett, James W. 1952. The study and interpretation of fish scales. The Science Counselor, vol. 15, No. 2, pp. 40-42. Monti, Rina. 1929. Biologia dei coregoni nei laghi italiani. Nota prima: La natura dei laghi nostri e I'introduzione dei coregoni. Istituto di Anatomia Comparata della R. Universita di Milano, Rivista di biologia, vol. 11, fasc 3-4 e 5-6, pp. 1-19. Istituto Editoriale Scientifico, Milano. Nelson, Merlin N., and Arthur D. Hasler. 1942. The growth, food, distribution and relative abundance of the fishes of Lake Geneva, Wiscon- sin, in 1941. Trans. Wisconsin Acad. Sciences, Arts, and Letters, vol. 34, pp. 137-148. Pearse, a. S. 1921. The distribution and food of the fishes of three Wisconsin lakes in summer. University of Wisconsin Studies in Science, No. 3, 61 pp. Madison. Pritchard, Andrew L. 1930. Spawning habits and fry of the cisco (Leucich- thys artedi) in Lake Ontario. Biological Board of Canada, Contributions Canadian Biology and Fisheries, N. S., vol. 6 (1930), No. 9, pp. 227-240. Toronto. 1931. Taxonomic and life history studies of the ciscoes of Lake Ontario. University of Toronto Studies, Publications Ontario Fisheries Re- search Lab., No. 41, 78 pp. 138 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE Rawson, D. S. 1930. The bottom fauna of Lake Simcoe and its role in the ecology of the lake. University of Toronto Studies, Publications Ontario Fisheries Research Lab., No. 40, 183 pp. Reighard, Jacob. 1915. An ecological reconnaissance of the fishes of Douglas Lake, Cheboygan County, Michigan, in midsummer. Bull. United States Bureau of Fisheries, vol. 33, Document No. 814, pp. 215- 249. Scott, W. B. 1951. Fluctuations in abundance of the Lake Erie Cisco {Leucichlhys artedi) population. Contri- butions Royal Ontario Museum of Zoology, No. 32, 41 pp. Scott, Will. 1931. The lakes of northeastern Indiana. Investi- gations of Indiana Lakes. III. Indiana De- partment of Conservation, Division of Fish and Game, Publ. No. 107, pp. 57-145. Smith, Oliver B., and John Van Oostbn. 1940. Tagging experiments with lake trout, white- fish, and other species of fish from Lake Michigan. Trans. American Fisheries Soc, vol. 69 (1939), pp. 63-84. Smith, Stanford H. 1954. Method of producing plastic impressions of fish scales without using heat. United States Department of the Interior, Fish and Wildlife Service, Progressive Fish-Culturist, vol. 16, No. 2, pp. 75-78. April. Stone, Udell B. 1938. Growth, habits, and fecundity of the ciscoes of Irondequoit Bay, New York. Trans. Ameri- can Fisheries Soc, vol. 67 (1937), pp. 234-245. SVARDSON, GUNNAR. 1951. The coregonid problem. III. Whitefish from the Baltic, successfully introduced into fresh waters in the north of Sweden. Fishery Board of Sweden, Institute of Freshwater Research, Rept. No. 32, Ann. Rept. 1950, pp. 79-125. Drottningholm. Thompson, D'Arcy W. 1942. On growth and form. 1,116 pp. The Mac- millan Co., New York. Van Oosten, John. 1923. The whitefishes {Coregonus clupeaformis) . A study of the scales of whitefishes of known ages. Zoologica, Scientific Contributions of the New York Zoological Soc, vol. 2, No. 17, pp. 380-412. 1929. Life history of the lake herring {Leucichlhys artedi LeSueur) of Lake Huron as revealed by its scales, with a critique of the scale method. Bull. U. S. Bureau of Fisheries, vol. 44 (1928), pp. 265-428. 1930. The disappearance of the Lake Erie cisco — a preliminary report. Trans. American Fisheries Soc, vol. 60, pp. 204-214. 1937. The age, growth, and sex ratio of the Lake Superior longjaw, Leucichlhys zenilhicus (Jordan and Evermann). Papers Michigan Acad. Sci- ences, Arts, and Letters, vol. 22 (1936), Zoology, pp. 691-711. 1939. The age, growth, sexual maturity, and sex ratio of the common whitefish, Coregonus clupea- formis (Mitchill), of Lake Huron. Papers Michigan Acad. Sciences, Arts, and Letters, vol. 24 (1938), Part II, pp. 195-221. Wagner, George. 1911. The Cisco of Green Lake, Wisconsin. Bull. Wisconsin Natural History Soc, vol. 9, Nos. 1-2, pp. 73-77. Milwaukee, Wis. Ward, Henry B. 1896. A biological examination of Lake Michigan in the Traverse Bay region. Bull. Michigan Fish Coram., No. 6, pp. 1-71. Lansing. WOHLSCHLAG, DoNALD E. 1953. Some characteristics of the fish populations in an Arctic Alaskan lake. In Current Biological Research in the Alaskan Arctic. Stanford LTni- versity Publications, University series. Biological Sciences, vol. 11, No. 1, pp. 19-29. U S. GOVERNMENT PRINTING OFFICE 1957 O — 388748 OBSERVATIONS ON THE DEVELOPMENT OF THE ATLANTIC SAILFISH ISTIOPHORUS AMERIC AN US (CITVIER), WITH NOTES ON AN UNIDEN- TIFIED SPECIES OF ISTIOPHORID Bv Jack W. Gehringer, Fishery Research Biologist The South Atlantic Fishery Investigations, con- ducted by the U. S. Fish and Wildhfe Service in cooperation with the U. S. Navy Hydrographic Office, the Office of Naval Research, the Georgia State Game and Fish Commission, and the Florida State Board of Conservation (through the Marine Laboratory, University of Miami), has engaged since July 1952 in a biological, chemical, and phy- sical oceanographic study of the waters between Cape Hatteras and the Florida Straits from the coast to considerably bej'ond the axis of the Gulf Stream. Field operations are conducted with the research vessel Theodore A\ Gill. Biological specimens are collected with standard half-meter silk nets, high- speed metal nets (Arnold and Gehrhiger, 1952), a continuous plankton sampler, 18-inch diameter dip nets equipped with 10-foot bamboo handles and lined with )^-inch nylon mesh, and trolling and hand lines. During hydrographic observations, at which time the vessel is drifting, dip-net operations are carried out, aided at night by flood and spotlights. Dip-netting sometimes produces relatively rare fish larvae and juveniles. Such was the case on July 29, 1953, between 1700 and 1900 hours dur- ing the occupation of regular station 30 (approxi- mately 90 miles east of Brunswick, Ga.) on Theodore N. Gill cruise 3, when several small istiophorids were captured. Dip-netting and sur- face tows on that station and on subsequent sta- tions produced a total of 26 specimens ranging in standard length from 3.4 to 38.8 mm. Since little has been pubUshed on the early life history of the sailfish and other istiophorids, in- formation that could be obtained from the speci- mens is of considerable value. There was a dearth of material in the 3.8-9.4 mm. range in our collections, however. The United States Na- tional Museum kindly loaned their small istio- phorid specimens, most of which were in the 3.8- 9.4 mm. range, including some from the Gulf of Mexico. I decided to include in the study all available material both from the waters off the South Atlantic Coast of the United States and from the Gulf of Mexico. Additional specimens were loaned by the Gulf Fishery Investigations (Arnold 1955) and various other organizations. Subsequent Theodore N. Gill cruises produced sev- eral more specimens; one was removed from the stomach of a small swordfish, Xiphias gladius (Arata 1954), and one was taken from the stomach of another small istiophorid. Three mounted specimens of Atlantic sailfish, Istiophorus ameri- canus (Cuvier), 374 to 625 mm. in standard length, were photographed and measured. In total, 168 specimens were examined. During my examination of the material I found two groups of fishes to be involved. Those below approximately 10 mm. in standard length did not separate into two groups on any character or group of characters examined, or location or time of cap- ture. The specimens exceeding approximately 10 mm. in standard length separated on some mor- phometric measurements into two distinct groups which converged at approximately 10 mm. The converging of the two groups at 10 mm. precludes the positive identification, by species, of speci- mens below 10 mm., so far as my observations are concerned. Beyond 10 mm. one group traces through development to the Atlantic sailfish, Istiophorus americanus (Cuvier). The other group, with a maximum size of 45.0 mm. stand- ard length, has not been identified. Lack of specimens exceeding 45 mm. makes positive iden- tification impossible. For these specimens I pre- sent selected measurements, counts, and figures, and discuss them with reference to Atlantic sail- fish specimens of similar sizes. The unidentified species is represented by 15 specimens exceeding 10 mm. Several specimens below 10 mm., which were taken at the same time as these, possibly belong to the same group. Though the taxonomy of the istiophorids is in 139 140 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE question, it is generally accepted that there is but one species of Atlantic sailfish: Istiophorus ameri- canus (Cuvier). In accordance with Bailey's re- view (1951) of the authorship of Cuvier and Valenciennes (1831), the single authority is used here as opposed to the common use of both names. Other members of the staff and members of the crew of the Theodore N. Gill assisted in the collec- tion of specimens and various other aspects of the study. Special thanks are extended to Isaac Ginsburg for loan of specimens and for critical reading of the manuscript; to Leonard P. Schultz of the U. S. National Museum for information and loan of specimens; to Royal D. Suttkus of Tulane University, Loren Woods, of the Chicago Natural History Museum, Giles W. Mead, Robert M. Yount of Myrtle Beach, S. C, and Tony Seaman of Morehead City, N. C, for loan of specimens; to Stewart Springer for data ; to Albert W. Collier, Jr., and Edgar L. Arnold, Jr., for loan of specimens and critical reading of the manuscript; and to Frank T. Knapp of the Georgia Game and Fish Commission and George F. Arata, Jr., of the Florida Board of Conservation, for critical reading of the manuscript. METHODS AND DATA METHODS OF MEASUREMENT Measurements from the specimens were made with a binocular, stereoscopic microscope and a micrometer eyepiece, except for the three mounted specimens, whose measurements were made with vernier calipers. Measurements of specimens less Figure 1. — Areas of capture of specimens (excluding Beebe's and 3 mounted specimens) indicated by circled dots, the 100-fathom curve by dotted lines, and the approximate axis of the Gulf Stream by arrows. ATLANTIC SAILFISH 141 than 100 mm. in standard length were recorded to the nearest 0.1 mm., and tliose of specimens more than 100 mm. in standard length to the nearest millimeter. Measurements of Beebe's (1941), Voss's (1953), and Baughman's (1941a) specimens were taken from their papers. DEFINITIONS OF TERMS Standard length. — Tip of snout to tip of urost.vle or most posterior e.xtension of hypural segment. Total length. — Tip of snout to tip of caudal fin, or finfold. Head length. — Tip of snout to posterior extension of fleshy margin of opercle. Width of head. — Measurement of widest portion of brain case, at point where dorso-lateral keel of pterotic spine joins orbital crest. Depth of head. — Vertical measurement of head at posterior angle of jaw. Snout length. — Tip of snout to anterior margin of eye. Lower jaw length. — Tip of mandible to posterior angle of the jaw. Snout extension. — Tip of snout to mandible tip fwith mouth clo.sed). Eye diameter. — Horizontal measurement of eye. Pterotic spine length. — Tip of spine to point of attachment of dorso-medial keel of spine to head. Main preopercular spine length. — Tip of main preoper- cular spine to vertical at posterior edge of preopercle. Pectoral fin length. — Tip of pectoral fin to insertion. Pelvic fin length. — Tip of pelvic fin to insertion. Dorsal fin-ray lengths. — Tips to insertions. Teeth. — Number of teeth on one side each of the upper and lower jaws, Pterotic spine serrations. — Numbers of serrations on keels of left and right pterotic spines. Ratio of secondary preopercular spines. — Number of spines, in ratio, on left side of head. Number of dorsal, anal, and pectoral fin rays. — Counts are total numbers with no distinction made between spines and soft rays. MEASUREMENTS AND MERISTIC COUNTS Table 1 gives selected measurements and meristic counts from the 19 specimens described or figured; table 2 gives selected measurements from 13 Florida specimens described by Voss (1953); table 3 gives selected measurements from two specimens described by Beebe (1941), and 3 mounted specimens from the Gulf of Mexico, described by Baughman (1941a). Voss's, Beebe's, and Baughman's data are plotted with mine on the respective graphs. Table 1. — Selected measurements and meristic counts from 19 specimens described and figured Measurements and counts for specimen N 3. — 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 Measurements in mm: Standard length 3.6 3.8 2.0 1.1 1.4 0.5 1.0 0.0 0.7 0.4 1.2 4.7 4.9 2.2 1.3 1.2 0.7 1.2 0.1 0.7 0.7 1.3 0.8 0.1 none none none none none none 10 5.6 6.0 2.7 1.4 1.5 1.0 1.7 0.1 0.8 1.0 1.8 0.8 0.1 none none none none none none 13 6.4 7.1 3.5 1.7 1.8 1.3 2.4 0.1 1.1 0.8 2.1 1.2 0.2 8.1 9.6 3.9 2.0 2.3 1.2 2.3 0.2 1.3 0.6 2.4 1.3 0.6 9.5 11.0 4.7 2.2 2.5 1.5 2.7 0.2 1.5 0.6 1.5 1.5 1.4 1.1 11.3 12.5 5.6 2.3 2.5 2.4 3.3 0.4 1.3 1.0 2.0 1.2 1.2 0.9 1.3 1.6 14.6 16.7 7.0 2.6 3.1 3.2 4.7 0.7 1.7 1.0 1.8 1.8 2.4 1.9 2.4 2.3 2.1 18.2 20.6 9.5 2.7 3.4 5.0 5.3 2.1 1.8 0.8 2.3 2.0 3.6 3.2 3.6 3.9 3.7 20.9 23.8 10.7 2.9 3.8 5.7 5.9 2.0 2.1 1.1 3.0 2.2 4.5 2.9 4.5 4.8 4.7 4.5 3.6 51 43 45-44 18-19 18-17 2:2 49 23 17 27.4 30.7 12.9 3.1 3.7 7.4 6.9 3.3 2.3 0.9 2.4 2.7 5.8 5.4 7.1 7.2 6.3 42 52 48-43 15-14 17-16 " 'si 25 18 38 8 42.9 19.9 3.4 4.5 12.9 8.4 7.6 2.7 1.0 2.7 3.8 8.7 5.9 10.6 11.5 11.1 6.6 9.3 55 SO 22-27 14-15 12-17 1:0 51 24 20 56.2 61.0 29.3 3.6 5.1 21.6 10.8 14.6 3.1 0.6 2.7 5.4 13.5 8.4 15.6 18.2 17.4 16.8 15.6 86 60 64.1 68.9 32.6 3.9 5.7 23.9 11.1 16.6 3.0 1.0 2.1 5.1 14.5 7.7 17.3 18.6 18.6 18.0 16.2 60 85 .. 43 101 54' 8 16 31 4 1 ...... 119 374 419 168 "'"35" 127 55 79 8 none none 21 '11.3 13.1 5.2 2.3 2.6 1.7 3.1 0.1 1.6 1.0 2.3 1.5 1.8 1.2 ■21.0 24.6 9.0 3.4 4.2 3.0 5.1 0.3 2.6 0.9 1.6 3.0 6.1 6.3 6.3 6.2 6.0 5.7 4.8 36 43 33-10 11-16 12-15 '45.0 Total length 50.5 15.2 Head width Head depth 4.8 7.2 5.2 8.5 0.8 Eye diameter Pterutlc spine length Main preopercular spine length 3.6 0.6 1.8 6.0 Pelvic fln length Dorsal fln-ray lengths: 5th none none none none none none none 13.5 12.0 15.6 26 16.4 15th 1.2 16.2 16.1 15.0 Counts: Number of teeth one side of jaw: 14 18 28 -- 10 -- 26 25 27 26 28... 43 48 37-36 16-21 1&-16 1:1 SO 23 18 45 46 37-38 16-15 18-18 2:2 52 22 16 34 34 34-34 16-18 15-18 2:1 J 42 16 14 102 SO Pterotic spine serrations: Dorso-lateral keel (left & right) 22-28 17-14 30-34 ... 18 .. 30 -. 12 none none none none 35-42 Dorso-medial keel (left & right) 14 10 Ventral keel (left & 14... 2:1 50 22 18 -. 11 12-13 Ratio of secondary pre- opercular spines (upper: 1:0 fold fold fold 1:0 fold fold fold 1:1 fold fold fold 2:1 fold' 16 2:1 42 10 15 2:1 "40 22 16 Number of dorsal fln rays. - Number of anal fin rays . . . Number of pectoral fln rays 53 24 18 65 24 20 51 »20 18 44 23 20 49 24 18 > Indicates unidentified species. ' Indicates questionable values. 142 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE Table 2. — Selected measurements from 13 Florida specimens described by Voss (1963) (In millimeters] Specimen No. — Standard length Total length Head length Snout length Eye diameter Pterotic spine length Preoper- cular spine length Lower jaw length Pelvic fin length 1 3.9 4.8 5.5 6.3 8.0 15.0 19.5 20.0 20.5 29 5 37.5 70.0 208.0 4.2 5.4 6.5 7.3 ft 6 16.7 22.0 21.5 22.0 32.5 41.0 76.0 234.0 1.5 2.2 2.7 3.8 4.2 7.5 ft 7 9.8 10.9 15.9 18.6 39 94.0 0.5 0. B 0.8 1.2 1.3 3.8 5.0 5.0 5.7 10.0 12.4 28.7 76.0 0.5 0.7 0.9 1.1 1.3 1.6 2.0 0.4 0.8 0.9 0.8 0.8 0.8 0.7 0.8 1.0 1.0 1.1 0.4 0.7 0.3 1.4 1.9 1.1 2.6 2.5 2.3 2.3 2.6 2.8 2.2 0.7 1.2 1.8 1.9 2.3 5.1 5.6 6.2 5.8 7.5 8.9 12.5 37.0 3 0.2 4 5 0.8 6 1.6 7 4.0 g 2.2 9 2.0 2.4 2.8 3.7 3.5 10 --- 6.4 11 12 -- 15.0 13 46.0 Table 3.- — Selected measurements from 2 specimens described by Beebe (1941) and 3 mounted specimens described by Baughman {1941a) [In millimeters] Item Standard length. - Head length Snout length. Eye diameter Pterotic spine length Main preopercular spine length. Lower jaw length Snout extension Pelvic fin length Dorsal fln height Number of dorsal rays Number of pectoral rays Measurements from Beebe No. 1 No. 2 437 169 140 12 130 Measurements from Baughman No. 1 No. 2 No. 544 233 175 16 849.5 314 228.5 22 116 '264" 851 324 232 23 1 Measurements are conversions of Beebe's percent-of-standard-length values. DESCRIPTION OF SPECIMENS The importance of line drawings, in a develop- mental series of a fish, to portray metamorphic changes is well understood ; therefore I have chosen for illustration (to scale) only those sizes at which important changes are apparent. A complete description is given of the smallest specimen, and for other specimens a brief summary of important changes which have occurred from the preceding size is presented. A series of specimens ranging in standard length from 3.6 to 374 mm. is figured and discussed. Those exceeding 10 mm. in standard length separated into two readily distinguishable groups, one tracing through development to the Atlantic sailfish, Istiophorus americanus (Cuvier), and the other remaining unidentified. Those below 10 mm. did not separate into two distinct groups; hence they are treated as one. Drawings of three specimens of the unidentified species are pre- sented (figs. 23, 24, and 25), with discussion lim- ited to variations from sailfish. Various authors, Gunther (1873-74), Lutken (1880), Goode (1883), Beebe (1941), LaMonte and Marcy (1941), and Voss (1953), have pub- lished figures and descriptions of small sailfish singly or in series. Those described by Voss from waters off southern Florida constitute the most complete series. I am unable to explain the differences between my findings and those of the authors cited. For comparison with the series of illustrations of sailfish material studied, I include as figure 21 a photograph of a 437-mm. sailfish, from off Texas, described by Beebe (1941), and as figure 22 a line drawing of an adult sailfish to portray general outlines. LARVA, 3.6 MILLIMETERS (Fig. 2) Although the specimen is damaged, it is the smallest complete larva in the material studied, and is smaller than any specimen previously described. Head. — The jaws are equal, and the snout is not produced. The orbital crest originates anterior to the nostril, curves over the eye (with a large spine over the eye), and continues posteriorly as a serrated ridge continuous with the dorsolateral keel of the pterotic spine. The pterotic spine has 3 serrated keels (dorsolateral, dorsomedial, and ventral in position), is directed posteriorly and parallel to sagittal plane of the body, and prom- inent serrations on the dorsolateral keel diminish to minute notches on the ridge connecting with the orbital crest. The main preopercular spine has 3 serrated keels (dorsomedial, lateral, and ventromedial in position), arises from the posterior ventral edge of preopercle, is directed posteriorly at approximately a 45-degree angle to sagittal ATLANTIC SAILFISH 143 <^'''^ *l ^Umnfc Figure 2. — Larva, 3.6 millimeters long (U. S. Nat. Mus. No. 111814). plane of the body (when opercle is closed), and the ventromedial keel terminates anteriorly at the posterior angle of the lower jaw. The upper secondary preopercular spine is serrated and arises from posterior edge of the preopercle on a serrated keel continuous with the dorsomedial keel of the main preopercular spine. (See figure 3 for arrange- ment of head spines in the dorsal view of a 3.8- mm. specimen.) The keel on the face of the oper- cle is serrated and possesses a dominant, acute, and medially situated protuberance. Keels on lower jaw are serrated, and two in number; one arising from the lateral surface of the posterior portion of the jaw and possessing a dominant protuberance, and the other comprising the lower edge of the lower jaw. Teeth are few in number, large, with the anterior ones tusklike. The eye is large, with a diameter one-third the length of the head. The nostril is a single opening in the swollen anterior-basal portion of the orbital crest. Body. — The body is short and deep, the visceral sac distended with food, and mj'omeres and the rodlike urostyle are prominent. Fins. — The dorsal, caudal, and anal are a con- tinuous fold with indistinct supporting structures developing in the caudal portion. The pectoral is round, with indistinct supporting structures. No pelvic fins are present. Pigmentation. — Pigment has faded from long preservation, and that remaining is limited to a Figure 3. — Larva, 3.8 mm. {Theodore N. Gill collections), dorsal view of head showing spination and pigmentation. PS, pterotic spine; USPS, upper secondary preopercular spine; PFS, spine on face of preopercle; MPS, main preopercular spine (directed at 90° from sagittal plane of body as opercles are open, angle is 45° when opercles ure closed); OC, orbital crest (showing heavy spine over eye). 389133 O— 57- 144 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE few melanophores (faded to brown color) on the dorsal surface of the brain case. The eyes are black with white pupils (preservation caused a reversal of color from that of the live condition of white eyes and black pupils). LARVA, 4.7 MILLIMETERS (Fig. 4) The visceral sac was nearly empty and not so distended as in other specimens of similar size. The snout is slightly produced and extends beyond the tip of the mandible. The nostril opening has elongated. Pelvic fins are now present, as buds, and indistinct supporting structures have appeared in the dorsal and anal portions of the finfold (which is now notched anterior to the caudal portion), and some rays are discernible in the ventral por- tion of the caudal. LARVA, 5.6 MILLIMETERS (Fig. 5) The snout and mandible have elongated slightly. Fanglike teeth are present on the tip of the snout. The nostril is partially divided by developing flaps. A lower secondary preopercular spine h?.s appeared on the ventromedial keel of the main preopercular spine. Separation of the finfold into dorsal, caudal, and anal portions is distinct but not complete. Additional caudal rays have appeared, the urostyle has turned upward, and supporting structures in dorsal, anal, and pectoral fins are further developed, but not yet discernible as rays. LARVA, 5.4 MILLIMETERS (Fig. 6) The snout is more elongated and extends farther beyond the tip of the mandible. Several palatine teeth have appeared, and although snout fangs are missing (appear broken off) they are present on other specimens of similar size. Each nostril is now divided (by a flap of skin) into two openings. Two upper secondary preopercular spines are now present. (At this size the height of spinous con- dition of the head is reached, although the pterotic spines are blunt and appear deformed on this specimen.) Rays are discernible in dorsal and anal fins, the pectoral fin has 16 rays, additional rays are present in the caudal fin, separation of dorsal, anal, and caudal fins is complete, and the pelvic fins have elongated. The pattern of pig- mentation is more distinct (probably owing to better color preservation). Figure 4. — Larva, 4.7 millimeters long (USNM 163332). Figure 5.— Larva, 5.6 millimeters long (USNM 163333). ATLANTIC SAILFISH 145 FioiRE 6.— Larva, 6.4 millinipters long (USX.M 111814). LARVA, 8.1 MILLIMETERS (Fig. 7) The snout extends farther beyond the tip of the mandible. Many teeth of varied sizes are present in both jaws, and fanglike teeth occur on the tip of the mandible. There are 42 rays in the dorsal fin, 10 in tiie anal, 15 in the pectoral, and 2 in the pelvic (posterior rays in dorsal fin are less clearly defined than anterior ones), and the caudal fin is notched. The pattern of pigmentation extends over a greater area. LARVA, 9.5 MILLIMETERS (Fig. 8) The anterior opening of each nostril has a collar (formed by a flap of skm). A second lower secondary preopercular spine is present on the left main preopercular spine, but a similar spine was not found on the right main spine, or on either spine of other specimens of similar size. The dorsal fin has increased in height, and when depressed fits into a groove formed from a raised dermal flap on each side of fin (groove ends at FiGiRE 7.— Larva, 8.1 millimeters long (USNM 111814). Figure 8.— Larva, 9.5 millimeters long (USXM 1 11814). 146 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE approximately the 25th ray) ; the anal fin has 22 rays; the pectoral fin is quite angular; and the pelvic fins have elongated. Pigment is present on lower middle portion of the dorsal fin. SAILFISH LARVA, 11.3 MILLIMETERS (Fig. 9) The snout has elongated, but there has been a corresponding elongation of the mandible, and the snout extension remains unchanged. The diameter of the eye is approximately one-quarter the head length (one-third on the previous speci- mens). The keel on the face of the preopercle is damaged so that no serrations are evident. The dorsal fin has 50 rays, the anal fin 22 rays, and the pectoral fin 18 rays (the full complement of rays has been reached in these 3 fins). The pelvic fins are slightly shorter on this specimen. A groove for the pelvic fins has appeared as an indentation of the belly. SAILFISH LARVA, 14.6 MILLIMETERS (Fig. 10) There is marked elongation of the snout and extension beyond tip of mandible. The teeth are more numerous, with those on the lower jaw more closely set than those on the upper. There is a marked increase in height of dorsal fin, and the the anal fin has 23 rays. A 3-toothed (or 3- pronged) scale, arising from the pectoral girdle, is situated on each side of the body just below the tip of the pterotic spine. There is a general increase in density of pigment. SAILFISH LARVA, 18.2 MILLIMETERS (Fig. 11) The snout is markedly produced (approximately one-half the head length) and extends two-fifths its length beyond the tip of the mandible. Teeth are more numerous. The eye diameter is approxi- mately one-fifth the head length. There is a marked heightening in anterior portion of the dorsal fin and a change in shape, and pelvic fins have lengthened and a third ray has appeared (constituting the full complement). A second 3-toothed scale is found on each side of the body at the pectoral girdle. The caudal peduncle is proportionately more slender. Pigmentation ex- tends over the entire anterior portion of the dorsal fin. Figure 9.— Sailflsh larva, 11.3 millimeters long (USNM 163333). ^^Jr^S^ Figure 10.— Sailfish larva, 14.6 millimeters long. From Theodore N. Gill collections. ATLANTIC SAILFISH 147 SAILFISH LARVA. 20.9 MILLIMETERS (Fig. 12) All rays in tlie dorsal and anal fins extend (for the first time) to fin margins, and the dorsal fin groove extends the entire length of the dorsal fin (previously approximately two-thirds tlie length of the fin). SAILFISH LARVA, 27.4 MILLIMETERS (Fig. 13) The snout is three-fifths tlie head length. Fangs liave disappeared from the snout tip. The eye diameter is approximately one-sixth the head length (previously one-fifth). A small pore is discernible on each side of the snout just anterior to the nostril. The dorsal fin has increased in height, and the anal fin is indented in central portion. SAILFISH LARVA, 38.8 MILLIMETERS (Fig. 14) The snout extends for one-half its length beyond the tip of the mandible. Teetii are fewer in number in the part of the upper jaw extending beyond tip of mandible. Two pores are present on each side of the snout, one anterior to and one below each nostril. The dorsal fin is higher and more uneven in outline, and an anal fin groove has appeared (formed by a dermal flap on each side of fin). The lateral line is discernible for the first time. The pigmentation has developed into distinct patterns on the body and the dorsal fin. SAILFISH LARVA, 56.2 MILLIMETERS (Fig. 15) The snout is markedly produced (three-quarters the head length) and extends for approximately Figure 11. — Sailfish larva, 18.2 millimeters long. From Theodore N. Gill collections. Figure 12. — Sailfish larva, 20.9 millimeters long. From Theodore N. Gill collections. 148 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE Figure 13. — Sailfish larva, 27.4 millimeters long. From Theodore N. Gill collections. Figure 14. — Sailfish larva, 38.8 millimeters long. From Theodore N. Oill collections. Figure 15.— Sailfish larva, 56.2 millimeters long (USNM 163413). ATLANTIC SAILFISH 149 t\vo-thii-(ls of its length boyoiul the tip of tlic maiulible. Tlie margin of the preopercle is serrated, but no secondary preopercular spines are discernible. The eye diameter is one-tenth the head length. The body is slimmer. The dorsal fin is higher, the pectoral fin longer and more angular, the aiu^l fin has a pronounced notch in its middle portion, and the pelvic fin has increased in length. Dermal spines are present over opercle, preopercle, and body except for the area covered by the pectoral fin (when depressed), but only the tips of the spines protrude through the skin (spines are discernible on a 43-mm. speci- men). Dermal spines are fully described in discussion of 64.1-mm. specimen. Pattern of pigmentation on the body is more pronounced. SAILFISH LARVA, 64.1 MILLIMETERS (Figs. 16 and 17) Teeth on the snout beyond mandible tip are weak and few in number, and palatine teeth are FiGURK 16. — Sailfish larva, 64.1 millimeters long (Alaska collections); view of head and teeth, orbital crest, small pores on snout, and serrations on lower jaw. present in two patches on each side on upper jaw (one below tlie nostril and one near the mandible tip). The arrangement of teeth in the lower jaw and posterior portion of upper jaw is portrayed in figure 16. Several pores are present on the snout near the nostrils (fig. 16). The minute dermal spines present on the opercle, preopercle, and uniformly over the body arise from ill-defined plates. The spines are narrow-based, acutely tipped cones which protrude through the skin (fig. 17). The interspinous distance varies from one to two times the spine height. Figure 17. — Sailfish larva, 64.1 millimeters long (^/asfca collections) ; oblique view of dermal spines, with tips of spines protruding through the sliin. SAILFISH LARVA, 101 MILLIMETERS (Figs. 18 and 19) Although the specimen is in poor condition and incomplete, many important characters remain. The snout is four-fifths the head length and extends for three-quarters its length beyond the tip of the mandible. Teeth are few in number in the portion of the upper jaw extending beyond the mandible tip. The serrated keels have dis- appeared from the lower jaw. (Although not shown in figure 18. serrations on the orbital crest Figure 18.— Sailfish larva, 101 millimeters long (USNM 107200). 150 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE and pterotic and main preopercular spines remain distinct.) The dermal spines are long, slender, with a gradual taper, and arise from the centers of irregularly shaped (though generally rounded) plates which appear slightly superior to connective tissues. The plates (or bases) have 3 or 4 con- centric raised ridges connected at random by numerous raised radials. The concentric ridges make a continuous spiral on some plates, but on others are entirely separate ridges (fig. 19). FiCiURE 19. — Sailfish larva, 101 millimeters long (USNM 107200): Above, dorsal view of dermal scale; below, oblique view. Diameter of scale approximately 0.6 mil- limeter. SAILFISH JUVENILE, 374 MILLIMETERS (Fig. 20) Observations are from a mounted specimen, and only those that appear accurate are presented (the first dorsal fin and the pelvic fins are artificial). There is no evidence of spines or serrated keels on the head. The only evidence of teeth are minute spines present mainly on the ventral surface of the snout in the portion extending beyond the tip of the mandible. Tlie caudal fin lobes are long and falcate, and the anal fin is separated. GROWTH AND DEVELOPMENT CHANGES IN RATES OF GROWTH OF VARIOUS BODY PARTS Several of the numerous measurements and meristic counts taken from the 168 specimens examined were selected to portray changes in rates of growth of various body parts. Original meas- urements were used in establishing the curves appearing in figures 26 to 35. As the graphs are largely self-explanatory, only the salient points are summarized. The curves are drawn to include all specimens less than 10 mm. in standard length, but only the Atlantic sailfish beyond 10 mm. It was considered that insufficient data were available to fit curves for the unidentified species. The fol- lowing comments apply only to the Atlantic sailfish. The rate of increase in head length approximates that of the standard length, with indications of a slightly higher rate in specimens smaller than 10 mm. (fig. 26). The rate of increase in head width approximates that of the standard length in specimens smaller than 10 mm. and falls well below it in specimens between 10 and 100 mm. (The high value for the 101-mm. specimen has been disregarded in drawing the curve, fig. 27.) The rate of increase in head depth approximates that of the standard length in specimens smaller than 10 mm., decreases and falls below it in specimens between 10 and 40 mm., and increases to approximate it in specimens exceeding 40 mm. (fig. 28). The rate of increase in snout length exceeds, considerably, that of the standard length in specimens smaller than 10 mm., decreases some- what (but still exceeds the standard length rate) in specimens between 10 and 100 mm., and falls slightly below it in specimens exceeding 100 mm. (fig. 29). The rate of increase in lower jaw length exceeds that of the standard length in specimens smaller than 10 mm., decreases and falls below it in specimens between 10 and 100 mm., and increases to approximate it in specimens exceeding 100 mm. (fig. 30). ATLANTIC SAILFISH 151 FiGiRE 20. — Young sailfish, 374 millimeters long. (Mounted specimen.) Captured in surf at Myrtle Beaoli. S. C. by hand, Aug. 3, 1952, by Robert M. and John Yount. The rate of increase in snout extension is con- stant and much higher than that of the standard length in specimens smaller than 50 mm., decreases gradually in specimens larger than 50 mm., so that it falls below that of the standard length in speci- mens exceeding 100 mm. (fig. 31). The rate of increase in eye diameter exceeds that of the standard length Ln specimens smaller than 10 mm., decreases to considerably less than it in specimens between 10 and 100 mm., and increases (but remains slightly below it) in specimens exceeding 100 mm. (fig. 32). The rate of increase in pterotic spine length is initially much higher than that of the standard length, but decreases sharply, and spine growth has ceased in specimens approximately 7 mm long (fig. 33). The rate of increase in the main preopercular spine length is initially much higher than that of the standard length, but decreases sharply, and spine growth has ceased in specimens approxi- mately 10 mm. long (fig. 33). The rate of increase in pelvic fin length exceeds, considerably, that of the standard length in specimens smaller than 10 mm., but decreased gradually in specimens between 10 and 20 mm., after which it approximates the standard length rate (fig. 34). The rate of increase in length of the longest dorsal ray (13th or 15th) exceeds that of the .■isni 3S <)— 57- 152 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE standard length in specimens between 10 and 20 mm., but decreases in specimens between 20 and 40 mm . , after which it approximates the standard length rate (fig. 35). DIVERGENCE IN MEASUREMENTS OF BODY PARTS FOR UNIDENTIFIED SPECIES The length of the snout shows the greatest divergence, which is evident at a smaller size than are other divergent characters. Since the snout length is reflected in the standard length, several graphs were constructed using "standard length minus snout length" as a base for comparison. The "weight" of snout length was thus removed from the base, and comparison of fish with similar body lengths was possible. The divergence in snout length (fig. 36), length of lower jaw (fig. 37), and snout extension (fig. 38), is more clearly defined than in plots against standard length (figs. 29, 30, and 31). When the eye diameter is plotted against snout length, the result is sub- stantially the same: divergence first evident at a standard length of approximately 10 mm. (fig. 39). Measurements of head depth, head width, aiul eye diameter, when plotted against "standard length minus snout length," revealed no marked divergence, at least below 20 mm. Values for the unidentified species plot either just above or among the higher values for the sailfish (also noticed in the plots of these values against stand- ard length, figs. 28, 27, and 32). Fk:t"Re21. — Sailfish, juvenile 437 iiiilliineters long, "20 inches total length, 437 mm. standard length; taken 3 miles off Aransas Pass, Texas, Aug. 31, 1941, by Aubrey Xelson " (Photograph courtesy of William Beebe.) J<^ FiQiRE 22. — General shape and proportions of adult sailfish. ATLANTIC SAILFISH 153 KiGiRE 23.— I'liiticiilifit'd spi'cics of larva, 1 1 .3 millimeters long. Theodore N. Gill t-oUeei ioi. FiniRE 24. — Unidentified .species of larva, 21.0 millimeters long, Theodore N. Gill collections FlGlTRE 25. — Unidentified species of larva, 45.0 millimeters long, Theodore X. Gill collect ions. 154 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 1 1 1 1 1 1 1 1 1 1 1 1 1 M 1 1 1 1 1 1 I I 1 1 _ I 600 - - 400 - g 200 - / y. 100 - y ^ -_ 60 - / - 40 - J/ / /■ / - 20 ■■■e 10 -_ /■• • - 6 - . yi ^•^ - 4 - - 2 1 o 1 1 1 1 i t 1 1 1 1 1 J 1 1 1 1 1 1 1 1 Mil 4 6 10 20 40 60 100 200 400 600 STANDARD LENGTH IN MM. Figure 26. — Relation of head length to standard length. Dots represent study specimens; x's, Beebe's specimens; circles, Voss's specimens; triangles, Baughman's specimens; and large black dots, the unindentified species. ~1 I I I I II I I "1 1 1 I I I M I "T 1 1 I I I I I I S a < e I I I I I I I I I J 1 I J I I I 4 6 10 20 40 60 100 200 400 600 STANDARD LENGTH IN MM. FiGUHE 27. — Relation of head width to standard length. Large black dots represent the unidentified species. ATLANTIC SAILFISH 155 60 40 20 n 1 — I — I I M 1 1 1 1 1 — I Mill -| 1 1 I I II I :H'- J I I I I I I I [ I I I r I r I I I I 1 I 10 20 40 60 100 STANDARD LENGTH IN MM. Figure 28. — Relation of head depth to standard length. Large black dots represent the unidentified species. DEVELOPMENT OF FIN RAYS Tables 4, 5, and 6 show the numbers of rays in the dorsal, anal, and pectoral fins of specimens of different sizes. Counts listed include both the Atlantic sailfish and the unidentified species. The following discussion of the numbers of rays in the fins applies only to the Atlantic sailfish for speci- mens exceeding 10 mm. Specimens below 10 mm. include both the Atlantic sailfish and the un- identified species. The number of rays in the dorsal fin of speci- mens which exceeded 10 mm. in length ranged from 47 to 57 (table 4). In those exceeding 26 mm. in length tiie full complement of rays is present, and the number ranged from 49 to 57, witii 75 percent having 49 to 53. The smallest specimen with a complement of 49 rays or more is 1 1 ..3 mm. in length, and tiie largest with fewer than this number is 16.2 mm. Table 4. —Dulrib ttion of specimens by length anc by number of rays in he dorsal Jin Length Number of specimens with ray count of— 42 43 44 45 46 47 48 49 50 SI 52 53 54 55 56 57 10.0-13.9 mm ... 14.0-17.9 mm.... 1 1 13 u 12 1 1 12 1 1 1 1 1 1 1(12) 3 1 3 1 5 2 1 ■I 3 1 1 «1 18.0-21.9 mm 22.0-25.9 mm.... 26.0-101 mm 1 Total ' 1 '3 ■3 12 1 1 3 3(1 2) 7 6 3(11) 3 1 1 1 1 1 Unidentified specimens. ' Specimen from Beebe (1941). 156 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE s g 10 _ 1 1 1 1 M 1 1 1 1 1 1 1 1 M 1 1 1 1 1 1 M 1 ; FIN RAY _ - y - A-'' y^ - / / / : - / - - / 3 - / / • • • : - - ■■>■ _ - 1 1 r 1 1 J 1 1 1 1 II 1 1 1 t 1 1 1 1.. 10 20 40 60 100 STANDARD LENGTH IN MM. FinuRE 29. — Relation of snout length to standard length. Dots represent study specimens; I's, Beebe's specimen circles, Voss's specimens; triangles, Baughman's specimens; and large black dots, the unidentified species. The number of rays in the anal fin of specimens between 6.0 and 9.9 mm. ranged from 20 to 22 (table 5). In sailfish specimens between 10 and 25.9 mm. the number ranged from 20 to 23. In specimens between 26 and 101 mm. the number ranged from 24 to 28 (excluding the 101-nim. specimen with a damaged anal fin whicli has 20 recognizable rays), with 92 percent having 24 to 26. I consider that the break at the 26-mm. size results from an inadequate sample. The smallest specimen with a complement of 22 or more rays is 9.5 mm., and the largest with fewer than this number (excluding the 101-mm. specimen men- tioned above) is 23.3 mm. 60 40 10 s Z 6 I •- 4 < 2 o ATLANTIC SAILFISH T 1 1 1 I I I I I 1 1 1 1 I MM 157 1 1 — I — I I I I J I 1 I 1 1 1 J I I I 1 1 1 I I I I 1 1 STANDARD LENGTH IN MM. Fi(!URE 30. — Relation of lower jaw length to standard length. Dut.s represent study specimens; x, Beebe's specimen; circles, Voss's specimens; triangles, Baughman's specimens; and large black dots, the unidentified species. Table 5. — Dislribution of specimens by length and by number of rays in the anal Jin Length Number of specimens with ray count of— 16 17 18 19 20 21 22 23 24 26 26 27 28 6.0-9.9 mm '4 1 2 ' 1 2 1('2) 1 1 2 1 1 1 1 1 1 U'l) 3 1 1 90 1) 20 1) 1 10.0-13.9 mm 14.0-17.9 mm 18.0-21.9 mm.-- - 22.0-25.9 nmi 26.0-101 mm.- 1 Total- '4 '2 1 1 5('2) 4 401) 40 2) 901) 20 1) 1 1 ' Unidentified specimens. Tlu' mimlier of rays in the pectoral fin of speei- nieiis i)et\veen 6.0 and 9.9 mm. ranged from l(j to 18 (table 6). Sailfisli exceetling 10 mm. in length had complements ranging from 16 rays to 20. In specimens exceeding 26 mm., the number ranged from 18 to 20, with 82 percent having 18 rays. The smallest specimen with a complement of 18 lays or more is 7.9 mm. in length, and the largest with fewer than this number is 23.3 mm. 158 600 400 200 - 60 40 Z o OT z Ui I- X bJ 3 O .2 - FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 1 1 1 — I Mill T 1 1 I M II I 1 I I I MM I .!. _l L ...jl^jM.!, I. L !. I lI J I I I 1 I I J I I I I I I 10 20 40 60 100 STANDARD LENGTH IN MM. Figure 31. Table 6. -Relation of snout extension to standard length. Dots represent .study specimens; x's, Beebe's specimens; and large black dots, the unidentified species. -Distribution of specimens by length and by num- ber of rays in the pectoral Jin Length Number of specimens with ray count of— 14 15 16 17 18 19 20 21 22 6.0-9.9 mm 10.0-13.9 mm 14.0-17.9 mm '1 '1 8 30 2) 2 1 1 1 1 1 2 20 4) 2 1 1401) '1 1 101) ' 1 20 1) n 18.0-21.9 mm. 22.0-25.9 mm 26.O-101 mm 1 1 Total 140 2) 20 1) 210 S) 201) 30 3) 11 Unidentified specimens. 'Specimen from Beebe (1941). SECONDARY PREOPERCULAR SPINES The numbers of upper and lower secondary preopercular spines, in ratios (for specimens with recognizable spines) are shown in table 7. A pat- tern (herein called ratio, upper: lower) prevails in the number of upper and lower spines for size groups, although considerable overlap of ratios is found. Of primary interest is the size at which the 2:1 ratio (apparently the iieiglit of normal spine development) occurs. Although several specimens smaller than 5.5 mm. have a 2:1 ratio, this ratio does not become dominant until a speci- ATLANTIC SAILFISH 159 men size of iippi'oximately 6.5 mm. Ri)ecimeMs exceeding 10 mm. have considerable variation, and on specimens exceeding 40 mm. the spines are difficult to discern. Until such time as identilication of specimens less than 10 mm. to species is accomplished, the pattern must be presented as representing one group. Table 7. — Distribution of specimens by length and by ratios of secondary preopercular spines standard length Number of specimens with spine ratio (upper:lower) of— 1:0 1:1 2:1 other ' 1 3 3.8 mm 2 1 3 2 1 5 1 1 4.0 mm .- 4.1 mm 1 4.3 mm ,. 2 1 4.5 mm - - . . - . . 4.6 mm . 3 2 2 3 1 .. 1 4.9 mm . . 3 5.1 mm - _ . . . 1 (2:0) 1 1 2 1 2 2 1 2 4 2 2 1 1 2 2 1 2 3 1 1 5.6 mm 1 5.7 mm. 1 2 .. 2 5.9 mm 1 (2:0) 1 (2:0) 1 6.1 mm 6.2 mm . 6.4 mm 2 6.5 mm 6.7 mm. . . 1 1 (2:2) 6.8mm. 6.9 mm 7.0 mm 3 1 2 1 1 3 7.3 mm 1 (2:0) 1 8.0 mm 8.1 mm... 1 (2:2) 8.6 mm . 1 1 1 1 »2 22 1 1 (3:1) 9.2 mm 9.4 mm 1 (2:3) 9.5 mm.. 10.3 mm. 10.6mm 10.8 mm 2 1 (2:2) 1 (2:2) 22 '1 1 11.4mm.. 12.3mm.. 2 1 (2:3) 2 1 (2:2) 12.8 mm.. 1 >2 13.0 mm 13.9 mm « 1 (3:2) 14.6mm-. 1 16.2 mm 1 1 1 16.9 mm 1 (2:2) 17.8 mm 18.2 mm 1 (2:2) 1 (2:2) 1 (3:1) 1 (3:3) 20.9mm 23.3 mm.. 29.6 mm 32.4 mm. 1 1 43.7 mm 1 (2:2) 1 Ratio shown In parentheses. 'Unlden tlfled sp€ clmens. PTEROTIC SPINE SERRATIONS The number of serrations on the dorsomedial and ventral keels of the pterotic spine ranges from 10 to 20, with but few exceptions, throughout the size range of specimens examined. The number of serrations on the dorsolateral keel in- creases from a range of 18-25 on 4-mm. specimens, to 24-42 on 10-mm. specimens, to 28-44 on 25-mm, specimens, and holds relatively stable between 44 and 49 on larger specimens.' We should expect less variation in number of serrations on keels of specimens exceeding 10 mm. in length, since growth of pterotic spines ceases when specimens are approximately 7 mm. in length (fig. 33). TEETH The number of teeth in relation to specimen size is shown in figure 40. For the sizes shown, there is an increase in number of teeth with an increase in specimen size; and the range is narrower in the sm.aller specimens than in the larger ones (many teeth of all sizes in larger specimens, but only a few well-developed ones in the smaller ones). Teeth were present in all specimens examined, but the 101-mm. specimen was badly damaged, and an accurate count could not be made. The remaining teeth of this specimen were not so large, relatively, as those of smaller specimens. Counts of 102 and 110 for one-half the upper jaw of the 45.0-mm. specimens of the unidentified species exceed those for Atlantic sailfish specimens to 64 mm . DEVELOPMENT OF PIGMENTATION Observations on the development of pigment include all specimens below 10 mm. in length, and only the Atlantic sailfish specimens above 10 mm. Notes on variations from this pattern of development in the luiidentified species follow the observations on the Atlantic sailfish. There are a few large melanophores on the dorsal surface of the brain case of the 3. 4-mm. specimen. There is a gradual increase in the pigmentation (consisting of small chromatophores) extending to the dorsal surfaces of the snout and the body on specimens approximately 4 mm. long, down the sides of the head and body posteriorly to the anus at approximately 5 mm., and to the ' Specimens of unidcntiru'd specie.'' 45.0 mm. long had counts of 37 and 50. otherwise, all counts for the species fell within those for Atlantic sailHsh. 160 FISHERY BULLETIN OF THE FISH AND "WILDLIFE SERVICE 60 40 1 6 (E 4 -| 1 1 1 I I I I I "T — I I I I I n I I I I 1 1 I I I I r I I I I I I I I J L_l_ _U 10 20 40 60 STANDARD LENGTH IN MM. Figure 32. — Relation of eye diameter to standard length. Dots represent study specimens; x's, Beebe's specimens; circles, Voss's specimens; triangles, Baughman's specimens; and large black dots, the unidentified species. caudal fin, witli increasing density, at appro.xi- mately 10 mm. The preopercle and opprcle are less densely pigmented than the dorsal part of the snout or body at any particular size. At the 6-mm. size, scattered melanophores appear in the pattern of chromatophores over the dorsal surface of the body. In specimens smaller than 10 mm., the dorsal surface of the brain case is pigmented by scattered melanophores. In specimens exceeding 10 mm., the pigmenta- tion changes little except for a gradual increase in density. Generally it is as follows: Upper jaw and sides of head, blue-black; mandible, non- pigmented; eye, silver with black pupil; upper body, dark blue to black; and lower sides of body anterior to the anus and caudal, blue. The belly is a silvery white, fins are usually ti-anslucent (except for the dorsal), and spines are nonpig- mented. Pigmentation on the dorsal fin develops from a scattering of chromatophores on the lower central portion at approximately 10 mm. to generally dense areas (with scattered less dense areas) at approximately 20 mm. Tips of dorsal fin rays are nonpigmented, and pigment on the dorsal fin extends posteriorly to approximately the 35th ray. Bars (or blotches) of chromato- phores appear on the body at approximately 35 mm. and persist through the size range of speci- mens examined. Color notes on fresh specimens (15-20 mm. in standard length) are as follows: Dorsal surface of head and body, steel-blue; sides of head and upper opercles, blue-black; eye, silver-wliite with a blue tinge and black pupil; ventral sides of body from anus posterior, blue; anal and pectoral fins, hyaline; caudal fin, translucent white; dorsal fin anterior portion generally blue-black with yellow and white streaks on rays, and posterior portion, hyaline; and ventral fins are tinged with yellow. The principal variations from this pattern of development in the unidentified species are as follows: (1) In general, the pigment on the dorsal ATLANTIC SAILFISH 161 o 111 .6 - < 2 S X 1- o z liJ < ID z O I IE T 1 1 — I Mill 1 1 1 — I I M I I Mill .-..-i*: /:• H — I I I I MM H — I I I I III ^... •• o I I I I I I I J I I I II II J I I I I 11 10 20 40 60 100 STANDARD LENGTH IN MM. FicURE 33. — Relation of head-spine lengths to standard length. Dots represent study specimens; x, Beebe's specimen; circles, Voss's specimens; and large black dots, the unidentified species. fin is present farther posteriorly than on tlie sail- fisli, and (2) there are no dark bars or blotches on the sides of the body, as are present on sailfish exceeding approximately 35 mm. in standard length. Color notes on live 35-45 mm. specimens of the unidentified species do not vary noticeably from those given above for the Atlantic sailfish. SUMMARY OF GENERAL GROWTH AND DEVELOP- MENT OF THE ATLANTIC SAILFISH = 1. From 3.4 to 7 mm., head spination develops • Points 1 and 2 are suniniarifS of development of all specimens below 11) mm., since no separation to species was made below this size. rapidly, and the pterotic spine growth ceases at approximately 7 mm. 2. From 7 to 10 mm., head spination reaches its maximum and no further development occurs, the snout begins to elongate, and rays begin to appear in the fins. 3. From 10 to 20 mm., the snout elongates farther and the snout extension increases, and the dorsal, anal, pelvic, and pectoral fins develop their full complement of rays. 4. From 20 to 50 mm., the snout elongates and snout extension increases, the dorsal, anal, pec- 162 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 60 40 o z lU > _l bJ -l 1 — I — I I I I I I 1 1 — I — I I I I 1 1 1 1 — I — I I I I I / ••/ I I 1 1 J I I I I I I 10 20 40 60 100 STANDARD LENGTH IN MM. 200 Figure 34. — Relation of pelvic fin length to standard length. Dots represent study specimens; x, Beebe's specimen: circles, Voss's specimens; triangles, Baughman's .specimens; and large black dots, the unidentified species. toral, and pelvic fins develop in size and shape, and dermal spines appear. 5. From 50 to 100 mm., the snout elongates farther, but the snout extension stabilizes, the dorsal and anal fins further develop in size, shape, and progress toward their eventual division, and dermal spines develop further. On the basis of the foregoing observations on growth and development, I have divided the specimens less than 100 mm. in length into three categories. The size range below 7 mm. lias been desig- nated "early larval," that period during which the head spines are developing (by 7 mm. all except the pterotic spine have ceased growing), and finfolds have little differentiation of rays. The size range from 7 to 20 mm. has been des- ignated "midlarval," that period during which all spine development ceases (at approximately 10 mm.), fins receive their full complement of rays and undergo changes in size and shape, and the snout begins to elongate. 600 - 400 200 20 >- < tn UJ O 2 o -l — I — I I I I 1 1 ATLANTIC SAILFISH 1 1 — I I I I I I 163 "T "T 1 — TTT / / I :a / J 1 1 1 1 1 1 1 1 1 1 10 20 40 60 100 STANDARD LENGTH IN MM. Figure 35. — Relation of length of longest dorsal fin-ray to standard length. Dots represent study specimens; x's, Beebe's specimens; and large black dots, the unidentified species. Tlie size range between 20 and 100 mm. has been designated "late larval," that period din-ing which head spines begin to disappear (although pterotic and main preopercular spines persist at 101 mm.), fins undergo other changes in size and shape (toward eventual division in dorsal and anal fins), dermal spines develop, and jaw teeth begin to disappear. While juvenile characters are developing within this range, it is my opinion that the important larval characters which per- sist preclude the use of the term "juvenile" for specimens below 100 mm. SUMMARY COMPARISON OF ATLANTIC SAILFISH WITH UNIDENTIFIED SPECIES A summary of the ])rincipal differences between specimens of the Atlantic sailfish and the imiden- tified species at comparalile sizes is outlined in table 8. 164 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE Table 8. — Comparison of certain characters from selected specimens of the Atlantic sailfish and the unidentified species Character Size Snout length Number of fin rays: Dorsal Anal Pectoral Size Snout length Snout extension Mandibular keels Number of fin rays: Dorsal Anal. -- Pectoral Longest dorsal fin ray . Dorsal fin, anterior lobe. Dorsal fin, pigment. ., Pelvic fin rays. Size Snout length Snout extension . . . Mandibular keels. Atlantic sailfish 11.3 mm ;s length of head . 20.9 mm-.-- -. ii length of head . . . ii length of snout . . Noticeably serrate . Number of fin rays: Dorsal- Anal Pectoral Longest dorsal fin ray. Dorsal fin, anterior lobe. Dorsal fin, pigment. -. Pelvic fin rays.. Body pigment-. Dermal spines-- 49 23 17 Number 13 to 15 Terminates at about the 25th ray. Extends posteriorly to 25th ray. Third is twice length of first. 38.8-56.2 mm ?5 to ?i length of head.. ii to ?4 length of snout. Present (minutely ser- rate) . Unidentified species 51-53---- ---- - 24 18-20 Number 13 to 15 Terminates at about the 40th ray. Extends posteriorly to 33-37th ray. Third is twice length of first. Distinct barred or blotched pattern. Discernible at 43 mm. as spines which pro- trude slightly through skin, uniformly dis- tributed over body. 11.3 mm. \i length of head. 42. 16. 14. 21.0 mm. H length of head. M length of snout. Minutely serrate. 44. 23. 20. Number 5. Terminates at about the 37th ray. Extends posteriorly to 37th ray. First and third equal in length. 45.0 mm. W length of head. M length of snout. Absent. 49. 24. 18. Number 13. Terminates at about the 40th ray. Extends posteriorly to the 4Qth ray. Third and first equal in length. No bars or blotches. Distinct spines arising from individual base plates, uniformly dis- tributed except for ir- regularly sized patches on body above lateral line (skin has worm track appearance). (Dermal spines resem- ble those in Beebe, 1941, text figure 2 for Istiophonts greyi Jordan & Hill— 84 mm.) FOOD HABITS Prior to Beebe's report (1941) that copepods are the primary food of small sailfish, and Voss's ob- servations (1953) on the food of postlarval and juvenile sailfish, little is found on the subject in the literature. The stomachs of 32 istiophorid specimens from the Theodore N. Gill collections were examined, and stomach contents are listed in table 9. With reference to this table it should be noted that copepods constituted the food of speci- mens less than 6 mm. long. At this size fish larvae also were eaten, and no specimen exceeding 13 mm. had copepods in its stomach. Voss (1953) also found evidence of change in the diet of young sailfish from copepods to fish larvae at a size of approximately 6 mm. Of particular interest are the small istiophorids removed from the stomachs of three of the speci- mens (one 10.2 mm. long from a 21.0-mm. speci- men, one 6.6 mm. long from a 13.0-mm. specimen, and part of one with a head 2.4 mm. long from a 16.2-mm. specimen). One specimen 6.0 mm. long removed from the stomach of a 21.9-mm. sword- fish {Xiphias gladius), Arata fl954), had copepods in its stomach. An unidentified species of fish oc- curred frequently in the stomachs of several speci- mens taken 90 miles east of Brunswick, Ga., July 29, 1953, and flying fish predominated in the stom- achs of others taken 150 miles east of Charleston, S. C, August 10, 1953. During the collection of the latter, small flying fish were also dipnetted. Small istiophorids were "relatively abundant" in the water when the above collections were made. Some fish larvae were larger than half the length of the fish that had eaten them. These data add support to the theory advanced by previous 1 — T 1 1 "^ m 1 60 40 - 20 - <»' 10 - *o ' 6 - 0- •CO 4 - 0-* • 2 - =«■■ • » • ••* • * • • _1_ I -J I I I I I I I J u I I I 2 4 6 10 20 40 60 STANDARD LENGTH MINUS SNOUT LENGTH, IN MM. FiGCRE 36. — Relation of snout length to standard length minus snout length. Large black dots represent the unidentified species. ATLANTIC SAILFISH 165 20 - I 1 I 1 1 1 1 I 1 1 1 1 1 1 I I 1 s z 10 - - 7 _ o • - I y- ~ O - • o — 7 UJ e _ _l i* * O , -35°N., 144°-173°E. in Nov. 1936- Feb. 1937; operational data, catch rates, water temperatures to 200 m; 1936 tana, landing statistics for the prefecture. 1941a. Albacore fishery. Chiba-ken suisan shiken- jo Katsuura bimj6 jigyo hokoku (1938) :1-21. [J.P] Results of participation in cooperative summer albacore longlining explorations, three cruises to 28°-43°N., 175°E.-175'' W., May- Aug. 1938; description of gear, operational data, finances, catch and prices, with water temperatures and spe- ific gravities to 200 m. 1941b. The skipjack fishery. Chiba-ken suisan shi- kenjo Katsuura bunjo jigyo hokoku (1938): 22-25. [J, P] Japan: albacore and skipjack fishing con- ditions correlated with water temperature. 1941c. Tuna fishery. Chiba-ken suisan shikenj6 Katsuura bimjo jigyo hokoku (1938) : 29-37. [J.P] Results of three longlining cruises to 29°- 37°N., 155°E.-178°W. in Nov. 1938-Feb. 1939; construction of gear, operational data, water temperatures to 200 m; catch and catch rates, principally albacore and bigeye. 1941d. Albacore fishery. Chiba-ken suisan shiken- jo Katsuura bunjo jigyo hokoku (1939) :1-13. [J.P] Results of participation in cooperative summer albacore longlining explorations, three cruises to 32°-45°N., 176°E.-176°W. in May-Oct. 1939; construction of gear, catch and prices; fishing logs with opera- tional data, water temperatures and speci- fic gravities to 200 m; albacore catch rates. 1941e. Skipjack fishery. Chiba-ken suisan shiken- jo Katsuura bunjo jigyo hokoku (1939) :14-17. [J.P] Landings of pole-and-line skipjack and al- bacore in the prefecture by months for 1938 and 1939; discussion of fishing con- ditions in each month relative to water temperatures. BIBLIOGRAPHY ON THE TUNAS 185 Chiba Prefectural fisheries experimental Sta- tion, KATSUURA Branch. — Continued 194 If. Tuna fishery. Chiba-ken suisan shikenjo Katsuura bunjo jigyo hokoku (1939) : 21-29. [J. P] Results of three longlining cruises, one for albacore to 30°-36° N., ITl'-lSO" E. in Nov.-Dec. and two for yellowfin, to 2°-6'' N., 130°-134° E. in April-May and to 5°-10° N., 131°-134° E. in 10° N., 131°-134° E. in Mar.-Apr. 1940; opera- tional data, water temperatures to 200 m., catch and catch rates for albacore, yel- lowfin, and bigeye. Chilton, Cyrus h. 1949. "Little tuna" of the Atlantic and Gulf coasts. Fish. Leafl., Wash. 353:1-5. [P] Euthynnus alletteratus : description. Chu, Yuanting T. 1931. Index piscium sinensium. Biol. Bull., Shang- hai 1:107-108. Auocis rochei, Neothunnus macropterus : synonymy, distribution. Cleaver, Fred c, and bell m. shimada. 1950. Japanese skipjack {Katsuwomis pelamis) fishing methods. Comm. Fish. Rev. 12(11) :1- 27. [P] History, biology and ecology, fishery for bait, fishing gear, fishing techniques, han- dling of catch, fishing grounds and sea- sons. Clemens, W. a., and G. V. Wilby. 1946. Fishes of the Pacific Coast of Canada. Bull. Fish. Res. Bd. Can. 48:164-167. Katsuwonus pelamis, Thunnus alalunga: description, distribution, food, records of capture in Canadian Pacific waters, fig- ured. CONNER, G. 1930. The five tunas and Mexico. Fish. Bull., Sac- ramento 20:75-89. Statistical records concerning the tuna catch and industry. CONRAD, M. G. 1937. The brain of the swordfish {Xiphias gtodius). Amer. Mus. Novit. 900:1-4. Comparison between brains of Xiphias, Scomber, Thunnus, and Euthynnus. COnseil International Pour L' exploration de la MER AND commission INTERNATIONALE POUR L' exploration SCIENTIFIQUE DE LA MER MfiDITERRANfiE. 1933. Conference d'experts pour I'examen des m6thodes scientifiques et techniques k ap- pliquer k I'^tude des poissons de la famille des Thonid^s. Rapp. Cons. Explor. Mer 84:92-103. [P] Brief reports of discussions of standardl- CONSEiL International. — Continued zation of techniques for tuna biology; T. thynnus, G. alalunga: nomenclature, sys- tematics, tagging, morphometric measure- ments, meristic counts, maturity, age and growth, statistics. COPLEY, H. 1947. Fish records and observations. Nat. E. Afr., Nairobi 2:9-10. Neothunnus macropterus: East African coast. CORWiN, Genevieve A. 1930. A bibliography of the tunas. Fish Bull., Sac- ramento 22:103 p. tPl Arranged alphabetically by author with brief annotations; covers the literature on tuna through 1929. Has a subject index, and a Ust of abbreviations used for period- icals cited. COWAN, Ian M. 1938. Some fish records from the coast of British Columbia. Copeia 1938(2) :97. Germo alalunga: recorded. CRANE, JOCELYN. 1936. Notes on the biology and ecology of giant tima, Thunnus thynnus Linnaeus, observed at Portland, Maine. Zoologica, N. Y., 21:207-212. Description, food, parasites, sex. De Beaufort, L. F., and W. M. Chapman. 1951. The fishes of the Indo- Australian tirchipelago. Volume 9:215-227. Leiden, E. J. Brill. [P] Euthynnus pelamis, Euthynnus allettera- tus affinis, Thunnus sibi, Thunnus macro- pterus, Thunnus tonggol, Auxis thazard. Figured: Euthynnus alletteratus, Thunnus macropterus. De Buen, Fernando. 1931. El supuesto paso por el Estrecho de Gibral- tar del atun en su emigraciOn gen^tica. Rapp. Comm. int. Mer M6dit. 6:405-409. Tuna (T. thynnus) : reproduction, migra- tion; Mediterranean Sea, Atlantic Ocean. 1930. Ictlologia espafiola: Scombriformes y Thun- niformes. Bol. Oceanogr. Pesc, Madr. 15(2): 33-53. [P] Key, distribution, Spanish and Basque common names: Germ,o alalunga, Thun- nus thynnus, Neothunnus albacora, Para- thunnus obesus, Auxis thazard, Euthyn- nus alletteratus, Katsuwonus pelamis. Sys- tematics, figures. 1932. Formas ontogtoicas de peces (Nota pri- mera). Notas Inst. esp. Oceanogr. Ser. II, no. 57:38 p. [P] Morphometries and descriptions: Auxis thazard, Sarda sarda, Thunnus thynnus. 1936. Fauna ictioldgica. Cat&logo de los peces ib6r- icos: de la planicie continental, aguas dulces. 186 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE De Buen, Fernando. — Continued peldgicos y de los abismos pr6ximos. Segunda parte. Notas Inst. esp. Oceanogr., Ser. II (89) ; : 91-149. [P] Synonymy: Germo alalunga, Thunnus thynnus, Neothunnus albacora, Auxis tha- zard, Eiithynnus alletteratus, Katsuwomis pelamis. 1937. Aires de ponte du thon (Thunnus thynnus L.). Int. Congr. Zool. 12:2123-2136. [P] Thunnus thynnus: spawning areas. De Buen, Feknando, and F. Frade. 1932. Clef dichotomique pour une classification ra- pide des poissons scombriformes. Rapp. Comm. int. Mer M6dit. 7(N.S.) :71-74. Classification, keys. De Jong, J. K. 1940. A preliminary investigation of the spawning habits of some fishes of the Java sea. Treubia 17(4):325-326. Euthynnus alUtteratus : frequencies of egg diameter measurements; resorption of eggs noted. De La tourrasse, Guy. 1951. La p§che aux thons sur la Cote Basque Fran- caise et son Evolution r^cente. Rev. Trav. Off. Peches marit. 17 (66fasc. 1) :42 p. [P] Thunnus thynnus and Oermo alalunga: distribution; fishing methods and boat design, trolling and livebait fishing. Delsman, H. C. 1931. Fish eggs and larvae from the Java Sea. Treubia 13(3/4) :407-409. Eggs and larvae believed to be those of Scomber (Delsman, Treubia 8(3/4:395-399), reidentified as Thyn- nus thunnina. 1933. Tunny in the North Sea. Nature 132(3338) : 640-641. Short note on the occurrence of Thun- nus thynnus in the North Sea since 1911. Delsman, H. C, and J. G. F. Hardenburg. 1934. De Indische zeevischen en zeevisscherij. Bibl. Ned. ind. nat. Ver. 6:330-343. Euthynnus alletteratus, E. pelamys, Neo- thunnus macropterus, N. rcwus: descrip- tion, distribution, key, Malayan names; spawning of E. alletteratus and descrip- tion of eggs and larvae; spawning of N. rarus and description of eggs; food of E. pelamys; E. alletteratus, and N. macrop- terus figured. DIEUZEIDE, R. 1930. Sur quelques scombriniens des cotes Alg6ri- ennes. Bull. Sta. Aquic. Peche Castiglione, 1929 (2e fasc.) :i33, 150-151, 159. Thunnus thynnus : classification. DIEUZEIDE, R. — Continued 1931. La p§che du thon a la ligne dans la bale de Castiglione. Bull. Sta. Aquic. PSche Castigli- one, 1930 (2e fasc.) : 107-127. Fishing gear and methods; Thunmis thyn- nus: Mediterranean. Domantay, Jose S. 1940a. The catching of live bait for tuna fishing in Mindanao. Philipp. J. Sci. 73(3) :337-342. [P] Description and figures of gear used; men- tions 16 species, mostly sardines, ancho- vies, and small scombroid and carangoid fishes, used as bait. 1940b. Tuna fishing in southern Mindanao. Philipp. J. Sci. 73(4) : 423-435. [P] Auxis thazard, Euthynnus yaito, Katsu- wonus pelamis, Neothunnus itosihi, N. ma- cropterus, Parathunntts sibi: distribution, figured; livebait fishing methods, gear, and boats. Dontcheff, Y., and R. Legendre. 1948. Thon blanc ou germon. Composition chimi- que et valeur alimentaire du germon. Rev. Trav. Off. Pgch. marit 11(44 fasc.4) : 447-462. Thunnus germo: chemical analysis. Dung, Dorothy I. Y., and William F. Rovce. 1953. Morphometric measurements of Pacific scom- brids. Spec. sci. Rept: Fish. U. S. Fish Wildl. : 95. [P] Morphometric data on: Neothunnus ma- cropterus, Parathunnus sibi, Germo ala- lunga, Katsuivonus pelamis, Thunnus thyn- nus, Thunnus orientalis, Thunnus maccoyii, Kishinoella tonggol, Euthynnus affinis, Gymnosarda nuda. ECKLES, Howard H. 1949a. Fishery exploration in the Hawaiian Islands (August to October 1948, by the vessel Oregon of the Pacific Exploration Company). Comm. Fish. Rev. 11(6) :l-9. [P] Euthynnus yaito, Katsuwonus pelamis, Neothunnus macropterus:. recorded; K. pelamis and N. macropterus: figured. 1949b. Observations on juvenile oceanic skipjack (Katsuwonus pelamis) from Hawaiian waters and sierra mackerel from the eastern Pacific. Fish. Bull., U. S. 51(48) : 245-250. [P] Katsuwonus pelamis: anatomy, descrip- tions, figfures and records of capture of juveniles; spawning; juveniles noted in stomachs of adults. Ego, Kenji, and TAMIO Otsu. 1952. Japanese tuna-mothership expeditions in the western equatorial Pacific Ocean, June 1950 to June 1951. Comm. Fish. Rev. 14(6):1-19. [P] i-'"' Catch statistics, prices. BIBLIOGRAPHY ON THE TUNAS 187 Ehrenbaum, E. 1934. Thunfische in den nordeuropaischen Gewas- sern. Fischmarkt 2(5) :116-119. Cuxhaven. Thunntis thynnus: migration, catch sta- tistics. ESPENSHADE, ADA V. 1948. Japanese fisheries production, 1908-1946. Fish. Leafl., Wash. 279:40 p. [P] Production of important species of fish In coastal waters (metric tons) : bonito (katsuo), tuna {maguro). Also chart showing pre-war areas fished for tima; table showing production of important species from offshore fisheries: bonito, tuna. Farina, Luigi. 1931a. L'attuale crisi dell' industria delle tonnare, cause e remidi. Boll. Pesca Piscic Idrobiol. 7(5):752-9. Mediterranean; statistics on trap catches. 1931b. Remarques sur les madragues des c6tes frangaises de I'Afrique du Nord. Bull. Soc. oc^anogr. Fr. 11(62) : 1115-6. Fishing gear and methods: traps; Medi- terranean; Atlantic Ocean. Federation of Japan Tuna and Bonito Fisheries Cooperative associations. 1951a. The present condition of the tuna fisheries. Katsuo to maguro 16:2-10. (In: Spec. sci. Rep: Fish U. S. Fish Wildl. 79) [P] Statistical tables on catch through 1949, size and composition of the fleet, number of fishermen, mothership operations, im- ports and exports. 1951b. The 1950 catch. Katsuo to maguro 19:2-8. [J.P] Statistics on tima catch, size and compo- sition of the livebait and longline fleets, average annual catch per vessel ton; comparisons with earlier years; mother- ship operations. 1952. The present condition of the tuna fisheries. Katsuo to maguro 26:2-12. [J, P] Tables of statistics on tuna catch, fleet, prices, exports, featuring 1947-50 average values. 1953a. The 1952 tuna catch. Katsuo to maguro 37:2-8. [J, P] Tables of statistics on catch of longline and livebait fisheries, catch per vessel ton, mothership operations, exports and imports. 1953b. The present condition of the tuna fisher- ies. Katsuo to maguro 39:2-13. [J, P] Strength and composition of fleet, num- ber of fishermen, catch statistics, catch Federation of Japan tuna. — Continued per vessel ton, price trends, operating costs, mothership operations, imports and exports; statistics through 1952. FERREIRA, ERNESTO. 1932. La pesca dell' albacora nelle Azzore. Note 1st. Biol. mar. Rovigno, No. 1. Thunnus gcrmo: fishing methods and gear, Atlantic Ocean. FICK, H. 1937. Der Fang von Thunf ischen und Heringshaien. Fischmarkt 5(1). Thunnus thynnus: North Sea. Fish, Marie p. 1948. Sonic fishes of the Pacific. Tech. Rep. Woods Hole oceanogr. Inst. 2:87-91. [P] Auxis thazard, Euthynnus, Germo ala- lunga, Katsuwonus pelaniis, Neothunnus macropterus, Thunnus thynnus: distribu- tion, English common names, synonymy of K. pelamis, G. alalunga, T. thynnus; air bladders of G. alalunga, N. macropterus, and T. thynnus described; Japanese com- :-■■ ','■« mon names of Euthynnus and T. thynnus; vertical distribution of Parathunnus me- bachi noted. Fisheries Society of Japan (Dai Nippon Suisankai). 1931. Illustrations of Japanese aquatic plants and animals, v.l. Tokyo. [P] Descriptions, figures of : Katsuwonus va- gans, Auxis thazard, Euthynnus yaito, Thunnus orientalis, Parathunnus sibi, Neo- thunnus macropterus, Germo germo, Sar- da orientalis. Fitch, John E. 1950. Notes on some Pacific fishes. CaUf. Fish Game 36(2) :65. [P] Stomach contents of Neothunnus macropterus. 1953. Extensions to known geographical distribu- tions of some marine fishes on the Pacific coast. Calif. Fish Game 39(4) : 539-52. [P] Euthynnus yaito: first record from the American Pacific coast. Flett, a. 1944. A report on livebait fishing for tuna in Aus- tralia. J. Commonw. sci. industr. Res. Organ. Aust. 17(1): 59-64 Tuna - livebait fishing. FOOD and agriculture organization of the United Nations. 1949a. General aspects of the world's tuna fisher- ies. Fish. Bull. F. A. O. 2(4) : 81-108. [P] World landings, distribution. 1949b. Recommended scientific and common names of important food fishes. A. Scombri- formes. Fish. Div., FAO, UN. 98 p. Auxis thazard, Euthynnus alletteraUta, 188 FISHERY BTJLLETIN OF THE FISH AND WILDLIFE SERVICE Food and Agriculture. — Continued Germo alalunga, Katsuwonus pelamis, Ne- othunnus macropterus, Thunnus thynnus: distribution; synonymy, world-wide com- mon names and recommended nomencla- ture. FORMOSA Government-General Fisheries experiment Station. 1930. Northern oceanographlc conditions and skip- jack fishing. Taiwan sotokufu suisan shikenjo suisan shiken hokoku, kaiyS chosa (1928) :67- 70. [J, P] Fishing conditions in relation to water temperature, specific gfravity, and cur- rents. 1931. Northern oceanographic conditions and skip- jack fishing. Taiwan sotokufu suisan shikenjo suisan shiken hokoku, kalyo chosa (1929) :28- 30. [J, P] Fishing conditions in relation to water temperature, specific gravity, and cur- rents. 1932. Northern oceanographic conditions {ind skip- jack fishing. Taiwan sStokufu suisan shlkenjd suisan shiken hokoku, kaiyo chosa (1930) :10- 11. [J,P] Fishing conditions in relation to water temperature, specific gravity, and cur- rents. 1933a. Oceanographic conditions and skipjack fishing in northern Formosa. Taiwan sotokufu suisan shikenjo jigyo hokoku, kaiyo chosa (1931) : 13-15. [J, P] Fishing conditions in relation to currents, surface water temperature, and specific gravity. 1933b. Experimental fishing and investigation in southern waters by the Shonan Maru. Taiwan suisan shikenjo jigyo hokoku, gyorobu ( 1931 ) : 1-50. [J,P] Yellowfin tuna: Indo-Pacific region; lengfth-weight data, fishing conditions in relation to oceanography and weather, catch per unit of effort, distribution, stomach contents. 1934. Oceanographic conditions and skipjack fish- ing in northern Formosa. Taiwan sotokufu suisan shikenjo jigryo hokoku, kaiyo chosa (1932): 10-12. [J, P] Fishing conditions in relation to currents, surface water temperature, and specific gravity. FortuniC, V. 1930. Crtice o ribarstvu uopde, a nada sve u po- druCju bivse republike dubrovaCke. 82 p. Fishing methods and gear, Adriatic Sea. FOWLER, Henry W. 1931. The fishes of Oceania. Supplement 1. Mem. Bishop Mus. 11(5) :325. [P] Euthynnus alletteratus, E. pelamis, Germo alalunga, G. macropterus, G. sihi, Thun- nus thunnus: listed, synonymy of G. ma- cropterus. 1933. Description of a new long-finned tima (S»ma- thunnus guildi) from Tahiti. Proc. Acad. nat. Sci. Philad. 85:163-164. Descriptions of a new genus Semathunnus and new species, Semathunnus guildi; Sem,athunnus distinguished from Neothun- nus. 1934. The fishes of Oceania. Supplement 2. Mem. Bishop Mus. 11(6) :400. [P] Euthynnus pelamis, Semathunnus guildi, S. itosibi, Thunnus orientalis: listed, syn- onymy. 1936. A synopsis of the fishes of China. VI. The mackerel and related fishes. Hongkong Nat. 7:61-80, 186-202. Thunnus thynnus, Neothunnus macrop- terus, Auxis thazard, keys, description, synonymy. 1938. The fishes of the George Vanderbilt South Pacific Expedition, 1937. Monogr. Acad. nat. Sci. Philad. 2:31-33, 253, 277. Auxis thazard, Euthynnus Kneatus, E. pel- amis: description, synonymy: Auxis tfca- zard, E. alletteratus, E. lineatus, E. pelam- is, Germo germo, Neothunnus macropter- us, Parathunnus sibi, Thunnus thynnus: recorded from Pacific. 1944. Results of the Fifth George Vanderbilt Ex- pedition (1941). Monogr. Acad. nat. Sci. Philad. 6:349, 373-4, 378, 498. Auxis thazard, Euthynnus lineatus, Kat- suwonus pelamis, Thunnus thynnus: re- cords of capture; synonymy. Pacific re- cords of A. thazard, E. alletteratus, E. lineatus, Germ,o alalunga, K. pelamis, Neo- thunnus argentivittatus, Thunnus thyn- nus; description of T. thynnus; figure of E. lineatus. 1949. The fishes of Oceania. Supplement 3. Mem. Bishop Mus. 12(2):73-74. [P] Auxis thazard, Euthynnus wallisi, Katsu- wonus vagans, Neothunnus macropterus, Parathunnus sibi: listed, synonymy. Frade, F. 1930a. Anomalies chez le thon rouge. Bull. Soc. portug. Sci. nat. 11(1) :l-5. [P] Describes abnormal structures or forma- tions in swim-bladder and head of Thun- nus thynnus. BIBLIOGRAPHY ON THE TUNAS 189 Frade, F. — Continued 1930b. L'anomalie faciale du thon rouge et son importance pour I'^tude des migrations. Bull. Soc. portug. Sci. nat. 11(2):7-10. [P] Discusses a certain anomaly, consisting of grooves on the side of the head, among red tunnies on the Portugese coast. 1931a. Donn^es biomdtriques pour I'^tude du thon rouge de I'Algarve. Bull. Soc. portug. Sci. nat. 11(7) :89-130. [P] Comparison of Atlantic and Tunisian T. thynnus. 1931b. Domi^es biom^triques sur trois espfeces de thons de I'Atlantique oriental. Rapp. Cons. Explor. Mer 10:117-126. [P] Thunniis thynnus, Parathunnus ohesus Lowe, Neothunnus albacora Lowe: mor- phometries. 1931c. Neothu7inus albacora (Lowe 1839). Faime ichthyol. Allan. N. 8. Description, synonymy, figure. 1931d. Sur le nombre des rayons des nageoires et de pinnules branchiales chez le thon rouge At- lantique. Bull. Soc. portug. Sci. nat. 11(10): 139-144. [P] Thunnus thynnus: anatomy. 1932. Sur les caractSres ost^ologiques k utiliser pour la determination des Thonid^s de I'Atlan- tique oriental et de la M^diterran^e. Rapp. Comm. int. Mer M6dit. 7:79-90. Osteology and specific identification of Thunniinae. 1935. Recherches biom^triques sur la maturity sexuelle du thon rouge. Trav. Stat. Biol, marit. Lisbonne 41. Thunnus thynnus: sexual maturity. 1937a. Recherches biom^triques sur la maturity sexuelle du thon rouge. Int. Congr. Zool. 12: 2137-2142. [P] Thunnus thynnus: sexual maturity. 1937b. Recherches sur la maturity sexuelle du thon rouge de I'Atlantique et de la M6diterran6e. Bull. Soc. portug. Sci. nat. 12:243-250. [P] Thunntis thynnus: sexual maturity. 1953. Sur r6tat de maturity sexuelle d'un germon pris en Mer Tyrrhenienne. J. Cons. int. Ex- plor. Mer 19(1) :72-76. [P] Thunnus germo: histological study of ma- turity of Mediterranean albacore, compar- ison with Atlantic population. Frade, f., and F. de Buen. 1932. Clef de classification principalement d'aprfes la morphologic interne. Poissona Scombri- Frade, F., and F. DE BUEN. — Continued formes (excepts la famille Scombridae). Rapp. Comm. int. Mer M6dit. 7(N.S.) :69-70. Classification; keys; anatomy, external and internal. Frade, Fernando, and S. Mana^as. 1933. Sur l'6tat de maturity des gonades chez le thon rouge gSn^tique. C. R. Ass. Anat., Apr. 10-12, 1933:1-15. [P] Thunnus thynnus: figures of ovaries and testes. Fraser-Brunner, a. 1949. On the fishes of the genus Euthynnus. Ann. Mag. nat. Hist. 2(20) : 622-628. [P] Euthynnus af finis af finis, E. af finis linea- tus, E. af finis yaito: classification, distri- bution, key, figures, synonymy. 1950. The fishes of the family Scombridae. Ann. Mag. nat. Hist. 3(26) :131-163. [P] Allothutmus fallai, Auxis thazard, Euthyn- nus af finis, E. pelamis, Thunnus alalunga, T. albacora, T. obesus, T. thynnus, T. tonggol, T. zacalles: classification, de- scription, distribution, key, figures, syno- nymy. FUJII, T. 1932. A study of the tunny fishery of Hokkaido. Bull. Sch. Fish. Hokkaido 2(l):32-47 [Je]. Thunnus thynnus: vertical migrations, variation of yield of the fishery in rela- tion to oceanographic changes. FUKUDA, M., and S. Iizuka. 1940a. Experimental tuna fishing. Kumamoto- ken suisan shikenjo jigyo hokoku 1938:15-20. [J.P] Bigeye tuna, black tuna: Ryukyu Islands; catch in relation to water temperature. 1940b. Skipjack tagging experiment. Kumamoto- ken suisan shikenjo jigyo hokoku 1938:21. [J,P] Japan: release records of tagged skipjack. Galtsoff, Paul S. 1952. Staining of growth rings in the vertebrae of tuna (Thunnus thynnus). Copeia 1952(2) : 103-105. [P] Ganssle, David, and H. B. Clemens. 1953. California-tagged albacore recovered off Japan. Calif. Fish Game 39(4) :443. Thunnus germo: tagging, migration; Pacific Ocean — northeast, northwest. Genovese, Sebastiano. 1952. Osservazioni idrologiche eseguite nella ton- nara del "Tono" (Milazzo) durante la cam- pagna di pesca 1952. Boll. Pesca Piscic. Idro- biol. 7 (U.S.), Fasc. 2:196-206. [P] Air temperature, water temperature, baro- 190 FISHERY BTJLLE3TIN OF THE FISH AND WILDLIFE SERVICE Genovese, Sebastiano. — Continued metric pressure, salinity, density, oxygen, transparency, currents during the fishing season (May-June) of a liorth Sicilian tuna trap for Thunnus thyitnus. 1953. Osservazioni idrologiche eseguite nelld toii- nara Capo San Marco (Sciacca) durante la campagna di pesca 1953. Boll. Pesca Piscic. Idrobiol. 8(n.s.), Fasc. 2:241-251. [P] Meteorological, hydrological data and catch records at a south Sicilian tuna trap; Thunnus thynnus: fishing season, average weight, notes on sexual maturity. GiNSBURG, Isaac. 1953. The taxonomic status and nomenclature of some Atlantic and Pacific populations of yellowfin and bluefin tunas. Copeia 1953(1) : 1-10. [P] Thunnus thynnus, T. secundodorsalis, T. saliens, T. albacares, T. subulatus, T. cata- linae, T. macropterus : synonymy. GODSIL, H. C. 1936. Tuna tagging. J. Cons. int. Explor. Mer ll(l):94-47. [P]. Description and figures of a strap-disk opercular tag used on yellowfin and skip- jack off California, together with the tools technique for applying it. 1937. The five tunas. Fish. Bull.; Sacramento 49:24-33. [P]. Catch statistics for yellovsrfin, bluefin, skipjack, albacore, and bonito in and ad- jacent to California waters. 1938a. The high seas tuna fishery of California. Fish. Bull., Sacramento 51:1-40. [P]. Yellowfin and skipjack fishing methods, capture of livebait, handling of catch. 1938b. Tuna tagging. Calif. Fish Game 24:245- 250. Skipjack, yellowfin tuna: tagging meth- ods and release records. 1938c. Tuna tags. J. Cons. Int. Explor. Mer 13(2): 217-220. [P] i Reports tagging of approximately 4,000 tuna on American Pacific coasts with, no recoveries; results of tests exposing ena- meled silver tags to sea water. 1945. The Pacific tunas. Calif. Fish Game 31 (4) ; 185-194. [P] Keys and figures for Katsuwonus pela- mis, Sarda lineolata,' Thunnus thynnus, Neothunnus macropterus, Thunnus alalun- ga, and Pan-athxmnua mebachi. GODSiL^ H. C. — Continued ; 1948. A preliminary population study of the yel- I lowfLn tuna and the albacore. Fish Bull., Sacramento 70:90 p. [P] Neothunnus macropterus, Thunnus gernio: morphometric data; population relation- ship of Japanese, Hawaiian, and Califor- nia fish analyzed; methods of taking mor- phometric measurements described. 1949a. A progress report on the tuna investiga- tions. Calif. Fish Game 35(1) :5-9. [P] Albacore, yellowfin tuna: summary of population studies based on morphometric analysis. 1949b. The tunas. In: The commercial fish catch off California for the year 1947 with an his- torical review 1916-1947. Fish Bull., Sacra- mento 74:11-27. [P] Catch statistics and distribution for Neo- .ifrt'J . ■"■ thunnus macropterus, Katsuivonua pela- mis, Thunnus germo, Thunnus thynnus; fishing methods briefly described. GODSIL, H. C, and R. D. Byers. 1944. A systematic study of the Pacific tunas. Fish Bull., Sacramento 60:131 p. [P] Katsuwonus pelamis, Neothunnus macrop- terus, Parathunnus mebachi, Thunnus ger- mo, T. thynnus: proportional measure- ments, methods of measurement, internal anatomy, key, figures, description, classl- ' ' ' ' f ication, counts of meristic characters, anatomical differences between species listed; population relationships discussed for all except P. mebachi. ''o .iv>r! GODSiL, H. C, and E. C. GREENHOOD. 1948. Some observations on the tunas of the Hawaiian region. Calif. Div. Fish Game. Bur. Mar. Fish. Mimeogr. Rep. Albacore, black skipjack, skipjack, yellow- fin tuna : distribution. 1951. A comparison of the populations of yellow- fin tuna, Neothunnus macropterus, from the eastern and central Pacific. Fish Bull.j Sacra- mento 82:1-33. [P] Comparative study of morphometric meas- urements of specimens from Hawaii, Pal- myra, Fiji, and the Pacific Coast of North America. A study of the homogeneity of the central Pacific stocks is also included. 1952. Observations on the occurrence of tunas in the eastern and central Pacific. Calif. Fish Game 38 ( 2 ) : 239-249. [P] Distribution of Thunnus germo, Neothun- nus macropterus, Katsuwonus pelamis. GODSIL, H. C, and E. K. Holmbekg. i 1950. A comparison of the bluefin ' tunas, genus BIBLIOGRAPHY ON THE TUNAS 191 GODSIL, H. C, and E. K. Holmberc}. — Continued Thunntis,. from New England, Australia, and California. Fish. Bull., Sacramento 77:1-55. [P] Atlantic bluefin (T. thynnus), California bluefin (T. thynnus), and Australian blue- fin (T. maccoyii) compared. Graham, David h. 1938. Fishes of Otago Harbour and adjacent seas with additions to previous records. Trans, roy. Sec. N.Z. 38(3) :414. Auxis thazard: listed. Green HOOD, E. C. 1952. Results of the examination of four small yellowfin tuna, Neothunnus macropterus. Calif. Fish Game 38(2) :157-163. [P] Morphometric and anatomical compari- son of three specimens from Hawaiian waters with one from Costa Rica, ranging 216 to 302 mm. in length. HadZi, J. 1934 ( ? ) . §to znamo danas o 2ivotu tunja. Rlbar- skiKalendar: 29-35. Tuna: Adriatic Sea. Hart, J. L., and H. J. Hollister. 1947. Notes on the albacore fishery. Progr. Rep. biol. Stas. Nanaimo and Prince Rupert 71:3-4. [P] Albacore catch correlated with water temperature and area; stomach contents. Hart, J. L., et al. 1948. Accumulated data on albacore (Thunnus alalunga). Circ. biol. Stas. Nanaimo and Prince Rupert 12 :5 p. [P] Thunnus alalunga: food, sizes landed in B. C, log records. Hasegawa, Kiichi. 1937. Progress report of experimental tuna fish- ing in waters adjacent to Woleai. Nany6 suisan joho 1:3-7. (Pacific Oceanic Fishery Investigations Translation No. 7. In: Spec, sci. Rep.: Fish. U. S. Fish Wildl. 46). [P] Yellowfin, bigeye, skipjack: longline catches in western Carolines; oceanogra- phic data from the fishing stations. hasegawa, KIMPEI. 1938. On a report of investigations of summer albacore. Kaiyo gyogyo 3(4) :14-31. [J] Germo alalunga : Pacific Ocean-northwest. Hatai, Shinkishi, et al. 1941. A symposium on the investigation of skip- jack and tuna spawning grounds. Kagaku nanyo 4(1) :64-75. (Pacific Oceanic Fish- ery Investigations Translation No. 16. In: Spec. sci. Rep: Fish. U. S. Fish Wildl. 18). [P] Skipjack: Japan, Indonesian waters, South Seas; eggs, juveniles, food, migration, Hatai, Shinkishi et al. — Continued sexual maturity, method of determining male and female skipjack. Black tuna: Japan, Philippine region; probable spawn- ing areas and season, sexual maturity, eggs. Yellowfin tuna: sexual maturity and probable spawning season in the Indo-Pacific area. Bigeye tuna: juveniles. Heldt, H. 1930. Le thon rouge et sa pgche, nouveaux aspects de la question. Bull. Sta. oc^anogr. Salamm- b6 18:69 p. [P] Thunnus thynnus: synonymy, anatomy, distribution, food, migrations, tropisms, spawning, growth, catch statistics, bibliog- raphy. 1931. Thunnus thynnus. In: Faune Ichthyologi- que de I'Atlantique Nord, No. 7. [P] Distribution, figure, description, brief synonymy. 1931. Le thon rouge et sa peche, ^l^ments d'un nouveau rapport. Bull. Sta. oc6anogr. Salamm- b6 21: 165 p. [P] Thunnus thynnus: figiared, synonymy, morphology, compared with T. secundo- dorsalis, biometry, meristic counts, distri- bution, migrations, spawning, growth, fish- ing methods, utilization, catch statistics, bibliography. 1932a. Rep^rage des bancs de thons par avion. Notes Sta. oc^anogr. Salammbo 26:12 p. [P] Aerial scouting for tuna schools in trap "• fishery off Moroccan coast; discussion of application of aircraft to tuna fishing and to the study of tuna migrations. 1932b. Le thon rouge et sa pfiche, rapport pour 1931. Bull. Sta. oc^anogr. Salammbd 29: 168 p. [P] Thunnus thynnus: figured, synonymy, "facial anomaly," meristic counts, distri- bution, migrations; tags, hooks, and har- poons figured; spawning, growth; fishing methods and gear, especially purse seine and trap; catch statistics, bibliography. 1934. Le thon rouge et sa p6che. Rapp. Comm. int. Mer M6dit. 8:187-255. Thunnus thynnus: food, migration, spawn- ing, statistics, development, bibliography. 1937. Le thon rouge et sa pfiche, rapport pour les ann^es 1933, 1934, et 1935 (9e Rapport). Rapp. Comm. int. Mer M^dit. 10:235-315. Thunnus thynnus: bionomics and fishery. 1938. Le thon rouge et sa pfiche. Rapp. Comm. int. Mer M6dit. 11 : 311-358. Thunnus thynnus: bionomics. 192 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE Heldt, H. — Continued 1943. fitudes sur le thon, la daurade, et les muges. Histoires d'^cailles et d'hamcQons. Broch Sta. oc^anogrr. Salammbd 1. Thunnus thynnus: growth; migration; Mediterranean Sea. 1950. Le germon (Germo alalunga Gmelin). fitude biolopque d'aprfes l'6xamen des 6cailles. Ann. biol., Copenhague 7:63-64. [P] Scale reading; age and growth. Herald, Earl S. 1949. Pipefishes and seahorses as food for tuna. Calif. Fish Game 35 (4): 329. [P] Euthynnus yaito, yellowfin tima: stomach contents. 1951. Pseudofins on the caudal peduncle of juve- nile scombroids. Calif. Fish Game 37(3): 335-337. [P] Auoeis thazard, Katsuwonus pelamis. Herre, Albert W. C. T. 1932. A check list of fishes recorded from Tahiti. J. Pan-Pacif. Res. Instn. 7(1) :3. [P] Euthynnus alletteratus, E. pelamis, Neo- thunnus macropterus: listed. 1933. A check list of fishes from Dumaguete, Oriental Negros, P.I., and its immediate vicin- ity. J. Pan-Pacif. Res. Instn. 8(4) :7. [P] Euthynnus yaito, Katsuwonus pelamis: lUted. 1935. A check list of the fishes of the Pelew Islands. Mid-Pacif. Mag. 47(2) : 164. [P] Katsuwonus pelamis, Neothunnus macrop- terus : listed. 1936. Fishes of the Crane Pacific Expedition. Zool. Ser. Field Mus. nat. Hist. 21:105-107. Katsuwonus pelamis, Neothunnus macrop- terus, Thunnus thynnus: distribution, syn- onymy, observations on N. m^wropterua fin lengths. 1940. Distribution of the mackerel-like fishes in the western Pacific north of the Equator. Proc. Pacif. Sci. Congr. 6th, vol. 3:211-215. [P] Auxis thazard, Euthynnus alletteratus, E. yaito, Germ.0 alalunga, Katsuwonus pela- mis, Neothunnus macropterus, N. rarus, Parathunnus sibi, Thunnus thynnus: dis- tribution. 1953. Check list of Philippine fishes. Res. Rep. U. S. Fish Wildl. 20:977. Synonymy, range. HERRE, Albert W. C. T., and A. F. Umali. 1948. English and local common names of Philip- pine fishes. Circ. U. S. Fish Wildl. Serv. 14: 128 p. [P] Herre, Albert W. C. T., and A. F. Umali. — Continued Auxis thazard, Euthynnus yaito, Oerm,o alalunga, Katsuwonus peUumis, Neothun- nus macropterus: listed. Hiatt, R. W., and V. E. BROCK. 1948. On the herding of prey and schooling of the black skipjack, Euthynnus yaito Klshi- nouye. Pac. Sci. 2(4) :297-298. [P] Euthynnus yaito: observations of herding of scads, Decapterus sanctae-helenae, in the Marshall Is. Higashi, Hideo. 1940a. Utilization of fishery byproducts from the South Seas (3). Nanyo suisan 6(7) :13-20. [J,P] Bigeye tuna, black tuna, skipjack, yellow- fin tima: ratio of viscera weight to body weight. 1940b. Utilization of fishery byproducts from the South Seas (7). Nanyo suisan 6(12) : 10-13. EJ.P] Skipjack: ratio of viscera weight to body weight; proportional measurements of various body parts. 1941a. Utilization of fishery byproducts from the South Seas (10). Nanyo suisan 7(3):32-39. [J.P] Katsuwonus vagans, Neothunnus macrop- terus: proportional measurements of vari- ous body parts; age analysis. 1941b. Utilization of fishery byproducts from the South Seas (14). Nanyo suisan 7(8) :36-43. [J,P] Bigeye tima, yellowfin tima : length-weight data; proportional measurements of vari- ous body parts; liver figured. 1942. Record of experiments on fishes of the South Seas. Nanyo suisan 8(11) : 13-27 [J,P] Katsuwonus vagans, Neothunnus macrop- terus, Parathunnus sibi: length-weight data; proportional measurements of vari- ous body parts. HiGASHi, Hideo, and M. Hirai. 1948. The nicotinic acid content of fish. Contrib. cent. Fish Sta. Japan (1946-1948) 18:129-132. Skipjack, yellowfin tuna: nicotinic acid content of various body parts. Hildebrand, Samuel F. 1946. A descriptive catalog of the shore fishes of Peru. Bull. U. S. nat. Mus. 189:361-372. [P] Euthynnus alletteratus, Katsuwonus pela- mis, Thunnus macropterus: classification; description, synonymy; distribution, food, key. Thunnus germo, T. thynnus: key, occurrences recorded. BIBLIOGRAPHY ON THE TUNAS 193 HIRATSUKA, HITOSHI, and KAKUJI IMAIZUMI. 1934. Experimental fishing and investigation in southern waters by the Shonan Maru. Taiwan sotokufu suisan shikenjo jigyo hokoku (gyo- robu) 1932:97-164. [J,P] Yellowfin tuna: Indo-Pacific region; length-weight data, fishing conditions in relation to oceanography and weather; catch per unit of effort; distribution. HIRATSUKA, HITOSHI, and KIYOJI ItO. 1934. Report on experimental tuna fishing in the Celebes Sea. Taiwan sotokufu suisan shiken- jo jigyo hokoku 1934:1-28. [J,P] Yellowfin tuna: length-weight data; fish- ing conditions in relation to oceanography and weather; catch per unit of effort; dis- tribution. HIRATSUKA, HITOSHI, and SEIICHI MORITA. 1935. Correlation between length and weight of yellowfin tuna. Taiwan suisan zasshi 241: 8-10. (Pacific Oceanic Fishery Investiga- tions Translation No. 26. In: Spec. sci. Rep.: Fish. U. S. Fish Wildl. 22) . [P] Neothunnus macropterus : Celebes Sea; morphometries. 1936. Correlation between length and weight of yellowfin tuna from the Celebes Sea. Suisan kenkyu shi 31 ( 1 ) : 67-68. [J] Neothunnus macropterus : length-weight relationship; Celebes Sea. HIKTZ, M. 1933. O tuni i tunolovu. Priroda 23(10) : 318-320. Adriatic Sea, fishing gear and methods. HORIGUCHI, YOSHISHIGE, D. KAKIMOTO, and KENiCHi Kashiwada. 1950. The distribution of inosite in the skipjack (Katsuwonus pelamis). Kagoshima sui sen ken ho 1:41-46. [J] Chemical analysis. HORIGUCHI, YOSHISHKJE, KENICHI KASHIWADA, and Daiichi Kakimoto. 1953. Biochemical studies on skipjack, Katsuwo- nus vagans. II. Contents of inorganic sub- stances in pyloric caeca. Bull. Jap. Soc. sci. Fish. 18(7) :279-282. [Je,P] Qualitative and quantitative analysis of the inorganic content of the pyloric caeca; quantitative results compared with those from analysis of muscle tissue. lEHISA, SATORU. 1939. Catch of tunny in the seas south of Kyushu. Bull. Jap. Soc. sci. Fish. 8(3) :143-144. [Je,P] Thunnus orientalis: catches correlated v«th water temperature. IKEBE, KenzO. 1938. Progress report on skipjack baitfish hold- ing experiments. Nanyo suisan joho 2(4): 2-4. [J.P] Skipjack live bait fishing: mortality of baitfish ( Spratelloides delicatulusf) held in pound net at Palau; water temperature, salinity, specific gravity. 1939a-1940. Four papers on the morphometry and age of tropical tunas. Nanyo suisan joho 3(10) :4 p; 4(1) :3 p; 4(2) :4 p; 4(5) :5 p. Pa- cific Oceanic Fishery Investigations Transla- tion No. 34. In: Spec. sci. Rep: Fish U. S. Fish Wildl. 22). [P] Length and weight data on Neothunnus macropterus, Makaira mitsukurii, Para- thU7inus mebachi, and Thunnus germo from Palau, the Marshalls, and Saipan; ages given based on Aikawa's age-size tables. 1939b. On the age of yellowfin taken in Palau waters. Nanyo suissin joho 3(10) :4-8. [J.P] Length-weight data, body condition, sex- ual maturity; age analysis based on size groups according to Aikawa's tables. 1940a. Age and measurements of timas in Palau waters. Nanyo suisan joho 4(1) :2-4. [J,P] Bigeye tuna, yellowfin tuna, striped mar- lin: length-weight data, condition factor; age analysis of yellowfin tuna based on size groups in accordance with Aikawa's tables. 1940b. Measurements of yellowfin tuna taken south of the Marshall Islands. Nanyo suisan j6h6 4 (2) :2-5. [J,P] Length-weight data on longline-caught fish, a total of 75 from 6 stations; age analysis based on size according to Aika- wa's tables. 1940c. Measurements of albacore and yellowfin tuna taken in Saipan waters. Nany6 suisan joho 4(5) :63-67. [J,P] Lengths and weights (gutted) of 8 alba- core and 58 yellowfin taken on longUnes north of Saipan; age analysis according to Aikawa's size age tables. 1940d. Investigation of tunas in Palau waters. Nany6 suisan joho 4(6): 2-4. [ J,P] Catches at 14 longlining stations near 7° N., 134°E.; surface temperatures and cur- rents noted; catch rates for yellowfin and spearfishes combined. 1941a. A survey of tuna fishing grounds in the Marshall and Caroline islands. Nanyo suisan joho 5(l):6-9. (Pacific Oceanic Fish- 194 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE IKEBE, KenzO. — Continued ery Investigations Translation No. 15 In: Spec. sci. Rep.: Fisli. U. S. Fish Wild. 47) [P] Catches from exploratory longlining in the Equatorial Countercurrent; currents at 10 fishing stations recorded; catch rates for tunas and marlins combined. 1941b. Measurements of yellowftn tuna from the Equatorial Countercurrent area. Nanyo suisan joho 5(3) :5-13. [J,P] Lengths, weights, sex, and estimated age (from Aikawa's tables) of 188 longline- caught yellowfin from 8 stations in south- em Carolines waters. 1941c. A contribution to the study of tuna spawn- ing grounds. Nanyo suisan joho 5(4): 9-12. [J,P] South Seas: probable tuna spawning grounds; lengths, weights, and estimated ages of 20 juvenile yellowfin, with dates and positions of capture. 1942. Report of the investigation of tuna fishing in the Timor, Arafura, and Banda seas. Nanyo suisan 8(1) :29-41. (Pacific Oceanic Fishery Investigations Translation No. 48. In: Spec. Sci. Rep: Fish. U. S. Fish Wildl. 45) [P] Bigeye tuna, yellowfin tuna: longline fish- ing conditions in relation to oceano- graphy; catches and catch rates at 10 stations. IKEBE, KenzO, and Takeshi matsumoto. 1937. Progress report on experimental skipjack fishing near Yap. Nanyo suisan joho 1(4) : 3-9. (Pacific Oceanic Fishery Investigations Trans- lation No. 6. In: Spec. sci. Rep.: Fish. U. S. Fildl. 46) [P] Results of 10 days' livebait fishing around Yap: fishing logs; lengths, weights, sex, and condition factor for 83 skipjack; water temperatures and salinities to 200 m. at 8 stations. 1938. Report of a skipjack bait investigation in Saipan waters. Nanyo suisan joho 6:2-12. (Pacific Oceanic Fishery Investigations Trans- lation No. 30. In: Spec. sci. Rep.: Fish. U. S. Fish Wildl. 44). [P] Common names and descriptions of the species used for livebait at Saipan; results of intensive experimental fishing for live- bait. IKEDA, NOBUYA. 1932. The bait problem and the development of our skipjack and mackerel fisheries. Miyagi no suisan 1:9-29. [J] Katsuwontis pelamis. Pacific Ocean-north- west; livebait fishing. IKEDA, NOBtTYA, and SEIJI AND6. 1933. A consideration of skipjack fishing conditions off northeastern Japan in 1930. Gyoro kenkyti- kai kaiho 5. [J] KatsHwonus pelamis. Pacific Ocean-north- west. IKEHAEA, Isaac I. 1953. Live-bait fishing for tuna in the central Pa- cific. Spec. sci. Rep.: Fish. U. S. Fish Wildl. 107:20 p. [P] Availability and characteristics of live- bait species of the Hawaiian, Line, and Phoenix islands; results of exploratory livebait fishing around these groups; size frequency distribution of yellowfin tima caught by livebait fishing in Line and Phoenix islands; evaluation of baiting grounds in the area. IMAI, Sadahiko. 1950. Studies on flying fishes. 1. On the young of flying fishes eaten by tuna. Kagoshima sui sen ken ho 1:137-148. [J] Tuna: food. IMAIZUMI, Kakuji. 1937. An account of the investigation of tuna fishing grounds in the East Philippine Sea. Taiwan suisan zasshi 271:6-23. [J,P] Popular account of an exploratory tuna longlining expedition: total catch and catch rates by species for 17 stations; brief remarks on maturity of yellowfin, distribution of catch rates, and oceano- graphic conditions. IMAMURA, YUTAKA. 1949. The skipjack fishery. Suisan koza 6:17-94. (Pacific Oceanic Fishery Investigations Trtms- lation No. 32. In: Spec, sci Rep.: Fish. U. S. Fish Wildl. 49). [P] Auxis hira, A. maru, Euthynntis yaito: Japan; description, distribution, habits. Katsuwonus pelamis: Japan; anatomy, description, migration, spawning areas and seasons, food, populations, habits, natural enemies, fishing conditions in relation to oceanography. 1953. The tuna fishery. Suisan koza 6:104 p. Tokyo. [J,P] General account of tuna livebait fishing, purse seining, gillnetting, trolling, and longlining; tables of operating and econ- omic data on Japanese longliners. INANAMI, YOSHIYUKI. 1940a. Relationship of viscera weight to body weight in yellowfin tuna. Nanyo suisan j6- h6 4(2):2-7. [J,P] Length, weight, body depth, body breadth. BIBLIOGRAPHY ON THE TUNAS 195 INANAMI, YOSHIYUKI.— Continued and weight of gills and viscera for 13 large longline-caught yellowfin; percen- tage of gill-and-viscera weight in body weight calculated. 1940b. Oceanography and fishing conditions in the sea area centered on Palau. Nanyo suisan jo- ho4(3):5-7. [J,P] Bigeye tuna, yellowfin tuna: longline fish- ing conditions in relation to currents and water color. 1940c. Tuna fishing conditions and currents along the eastern coast of the Palau Islands. Nanyo suisan joho 4(2) :7-10. [J,P] Bigeye tuna, yellowfin tuna: longline fish- ing conditions in relation to local currents at 47 stations within 30 miles of the coast. 1941. Report of oceanographic changes and fishing conditions in Palau waters. Nanyo suisan jo- ho 5(2) :2-6. (Pacific Oceanic Fishery Investi- gations Translation No. 3. In: Spec. sci. Rep.: Fish. U. S. Fish Wildl. 42) [P] Describes the effects of a southward shift of the Equatorial Counter-current on oceanographic conditions and on the skip- jack fishing at Palau. 1942a. Oceanographic conditions and yellowfin tuna fishing grounds in South Sea Islands wa- ters. Nanyo suisan joho 6(l):2-5. [J,P] Location of longline fishing grounds in re- lation to currents, transparency, water color, and water temperature in the equa- torial current system between 130°E. and 170°E. longitude. 1942b. Skipjack fishing conditions at Saipan, Truk, and Ponape. Nanyo suisan joho 6(1) :5-7. [J,P] Seasonal fluctuations in commercial catch and the size of fish taken. 1942c. Small skipjack caught at Truk. Nanyo sui- san joho 6(1) :7. [J,P] Records and measurements of two juve- niles. 1942d. Grounds fished by tima boats operating in the Inner South Seas. Nanyo suisan joho 6(1) : 7-9. [J,P] Albacore, bigeye, skipjack, yellowfin tu- na: fishing conditions in relation to water temperature; seasonal shifts in equatorial longlining grounds at 150°E. to leO'E. longitude. INOUE, MOTOO. 1953. Albacore fishing conditions and oceanogra- phic conditions in the 1952-53 longlining sea- son. Tokai daigaku sangyo kagaku kenkyusho INOUE, MOTOO. — Continued suisan kenkyubu gyogyo shiryo No. 3:17 p. [J.P] Thunnus gerino: fishing conditions in re- lation to oceanography, catch per unit of effort; Pacific Ocean — northwest. ISAWA, TAKAO. 1935. On the tuna of the Japan Sea coast of Hok- kaido. Hokkaido sui shi junpo 1935:727-731. [J] Tuna: distribution; Sea of Japan. IWATE PREFECTUKE FISHERIES EXPERIMENT STATION. 1953a. South Seas tuna fishing experiment report. 1:44 p. [J.P] Results of an exploratory longlining trip aroxmd 10°N., 170°W. Fishing logs; cur- rents, salinities and water temperatures to 300 m., plankton collections; distribu- tion of catch rates for N. macropterus, P. sibi, and black marlin; length frequen- cy curves, sex ratios and apparent ma- turity, notes on stomach contents, catch by branch line number and estimated depth; data on shipboard refrigeration and the prices received from each species landed. 1953b. South Seas tuna fishing experiment report. 2:31 p. [J,P] Results of an experimental longlining trip around 4°N., 175°W. Fishing logs; cur- rents, water temperatures and salinities to 300 m., plankton collections; length fre- quency distributions for N. macropterus, P. sibij and black marlin; catch rates; catch by branch line numbers and esti- mated depts; prices received for each spe- cies landed; sex ratios ajid apparent ma- turity. JAPANESE Bureau of Fisheries. 1933. Report of the southern fisheries investigation for 1931. Bur. Fish. Min. Agr. and For. (1931) 1933:96 p. [J,P] Results of tuna longlining and purse sein- ing by boats of the training ship Hakuyo Maru In the Celebes Sea and Indian Ocean; shipboard tuna canning experiment; com- plete logistical and operational data; catch and production (dried fish) of a land- based skipjack fishing operation in Bor- neo; fishing gear and boats described and figured; yellowfin and bigeye catch, catch rates, weather, and oceanographic data for 19 longline stations; observations of surface schools of skipjack and small yel- lowfin. 1934. Report of the soutbem fisheries investiga- tion for 1932. Bur. Fish. Min. Agr. and For. 196 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE Japanese Bureau of fisheries. — Continued (1932) 1934: 347 p. [J.P] Results of tuna longlining and purse sein- ing by boats of the factory ship Haruna Maru (1,500 tons) off the N. coast of Borneo and the W. coast of Sumatra; com- plete operational data; results of shipboard canning and freezing experiments; des- criptions and figures of fishing gear and boats; daily catches by species by each of 8 boats fishing up to 40 baskets of long- lines; catch rates given, positions of sets plotted; yellowfin stomach contents (non- quantitative) recorded for 66 samples of up to 29 fish, together with notes on plank- ton samples from the same stations; graph plotting yellowfin and bigeye catch rates with transparency and water temperature at 0, 100, and 150 meters. 1935. Report of the southern fisheries investigation for 1933. Bur. Fish. Min. Agr. and For. 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[J.P] Detailed results of exploratory albacore longlining by 11 research ships at 28°N.- 43°N., 165°E.-165°W. from May to Sep- tember; track charts and fishing logs; data on surface and subsurface water tem- peratures and salinities, correlated with catch rates; albacore .stomach contents noted; measurement and sex data; catch records also for bigeye, yellowfin, and skipjack. 1940. Results of encouragement given to the de- velopment of albacore fishing grounds during 1939. Bur. Fish., Min. Agr. and For. 1940: 173 p. (Translated as Spec. sci. Rep.: Fish. U. S. Fish Wildl. 33). [P] Detailed results of exploratory albacore longline fishing by 9 research ships at 30° N.-45°N., 163°E.-175°W. from May Japanese Bureau of fisheries. — Continued through October; track charts and fishing logs; data on surface and subsurface water temperatures and salinities, cor- related with albacore catch rates; stomach contents noted; measurement and sex data; catch records for bigeye also; data on plankton collections (nonquantitative). 1942. Results of encouragement given to the devel- opment of albacore fishing grounds during 1940. Bur. Fish. Min. Agr. and For. 1940: 135 p. [J] Results of exploratory albacore longlining in the central North Pacific. JOUBIN, M. (Ed.) 1934. Faune Ichthyologique de I'Atlantique Nord, No. 15. Copenhagen, Andr. Fred Host and Fils (published for Conseil Permanent International pour I'Exploration de la Mer). [P] Plates including description, synonymy, geographical distribution of: Germo ala- lunga, Atixis thazard, Katsuwonus pelamis, Euthynnus alletteratus, Sarda sarda. June, Fred C. 1950a. Preliminary fisheries survey of the Hawai- ian-Line Islands area. Part 1. The Hawaiian long-line fishery. Comm. Fish. Rev. 12(1) :1- 23. [P] Information on the boat, crew, description of gear, bait, setting the line, fishing areas and depths, amount and efficiency of gear used, catch composition. 1950b. The tuna industry in Hawaii. Pan-Amer. Fish. 4(10) : 11, 19. [P] Brief description of the skipjack (Katsu- wonus pelamis j fishery. 1951a. Preliminary fisheries survey of the Hawai- ian-Line Islands area. Part 2. Notes on the tuna and bait resources of the Hawaiian, Lee- ward, and Line Islands. Comm. Fish. Rev. 13(l):l-22. [P] Includes sea conditions, tuna and bait re- sources, for the Hawaiian Islands, Lee- ward Islands, Line Islands, and Canton Island. 1951b. Preliminary fisheries survey of the Ha- waiian Line Islands area. Part 3. The live- bait skipjack fishery of the Hawaiian Islands. Comm. Fish. Rev. 13(2) : 1-18. [P] Description and notes on biology of skip- jack, development of the fishery, fishing boats and crews, bait, fishing methods, fishing areas and seasons. 1952a. Observations on a specimen of bluefin tuna (Thunnus thynnus) taken in Hawaiian waters. Pacif. Sci. 6(1) :75-76. [P] Comparison with Thunnus orientalis; mor- BIBLIOGRAPHY ON THE TUNAS 197 jLi^NE, Frb:d C. — Continued phometric measurements and meristic counts of the specimen given. 1952b. An "unusual" yellowfin tuna (Neothunnus macroptenis) from the waters of the northern Line Islands in the central Pacific Ocean. Copeial952 (3):210-211. [P] Description of a 24-lb. female which be- cause of its coloration at first appeared to be a bluefin tuna (Thumius thynnus) or Thunnus maccoyi. Meristic counts and measurements indicated that it was a yellowfin tuna. 1953. Spawning of yellowfin tuna in Hawaiian waters. Fish. Bull., U. S., 54(77) :47-64. [P] Collection and treatment of ovary samples, description of the ovaries, development of the ova, relation of ovary size to fish size as a measure of maturity, number of ova spawned, spawning season, spawning and the fishing season. June, Fred C, and J. W. Reintjes. 1953. Common tuna-bait fishes of the central Pa- cific. Res. Rep. U. S. Fish. Wildl. 34:54 p. [P] Keys and descriptions of families and spe- cies of bait fishes: figures; evaluation of tuna bait resources in the central Pacific. K.\FUKU, TAKEICIURO. 1950. On the dark muscle tissue in fishes. (Rep. No. 1.) The dark muscle tissue of the tunas, from the viewpoint of comparative anatomy. Jap. J. Ichth., Tokyo 1(2) :89-100. [Je,P] Tuna: anatomy. KAGOSniMA PREFECTURE FISHERIES EXPERIMENT STATION. 1930a. Experimental skipjack fishing. Kagoshima- ken suisan shikenjo jigyo hokoku (1928) :1-18. [J,P] Results of 11 skipjack livebait fishing cruises off southern Japan, the Ryukyus, and northern Formosa from March to June: fishing logs; surface and subsurface water temperatures at fishing stations. 1930b. Experimental longline fishing for tuna. Kagoshima-ken suisan shikenjo jigyo hokoku (1928) :18-31. [J,P] Results of 3 longlining cruises from south- ern Japan to the Ryukyus between Novem- ber and February; bigeye, yellowfin, and albacore catches, correlated with tides; surface and subsurface water tempera- tures at fishing stations; fishing logs. 1930c. Experimental fishing by small motor ves- sels: experimental longline fishing for alba- core. Kagoshima-ken suisan shikenjo jigyo hokoku (1928): 54-60. KAGOSHIMA PREFECTURE FISHERIES EXPERIMENT Station. — Continued Results of 2 longlining cruises with a 20- ton vessel in Ryukyu waters in March and April; description of gear; albacore, yel- lowfin, and bigeye catch, surface and sub- surface water temperatures at fishing sta- tions; fishing logs, plots of sets. 1931a. Experimental skipjack fishing. Kagoshima- ken suisan shikenjo jigyo hokoku (1929) :1-16. [J.P] Results of 10 livebait skipjack fishing cruises in Ryukyu waters between March and June; average monthly surface water temperatures for 7 years; commercial fishing correlated with surface tempera- tures; a few subsurface temperature data; fishing logs. 1931b. Experimental longline fishing for tuna. Kagoshima-ken suisan shikenjo jigyo hokoku (1929) :16-30. [J,P] Results of 4 exploratory tuna longlining cruises in Ryukyu waters from October to January; average monthly water tempera- tures; catches of yellowfin, albacore, and bigeye tuna recorded with surface and subsurface temperatures at the stations, moon phase and tides, transparency; de- scription of gear; plot of station locations and fishing logs. 1932a. Experimental skipjack fishing. Kagoshima- ken suisan shikenjo jigyo hokoku (1930) :l-20. [J,P] Results of 9 livebait skipjack fishing cruises in Ryukyu waters from March to June; surface water temperature iso- therms plotted; fishing logs and plot of station locations. 1932b. Experimental longline fishing for tuna. Kagoshima-ken suisan shikenjo jigyo hokoku (1930) : 21-28. [J,P] Results of 7 exploratory tuna longlining cruises in Ryukyu waters from October to February; catches of yellowfin, bigeye, and black tuna recorded with surface and subsurface temperatures at fishing sta- tions; fishing logs and plot of station lo- cations. 1932c. Experimental longline fishing for albacore and pole and line fishing for mackerel. Kago- shima-ken suisan shikenjo jigyo hokoku (1930) 54-59. [J,P] Results of 3 exploratory longlining stations in Ryukyu waters in March; catch (a total of 3 albacore) recorded with surface and subsurface temperatures on the stations; fishing logs and plot of station locations. 198 FISHEKY BULLETIN OF THE FISH AND WILDLIFE SERVICE KAGOSHIMA PEEFECTURE FISHERIES EXPERIMENT Station. — Continued 1933a. Investigation of skipjack fishing. Kagoshi- ma-ken suisan shikenjo jigyo hokoku (1931) : 1-16. [J,P] Results of 8 exploratory live-bait skip- jack fishing cruises in Ryukyu, Formosan, and Philippines waters from March to June; fishing logs and plots of station lo- cations; surface temperatures discussed, isotherms plotted. 1933b. Experimental longline fishing for tuna. Ka- goshima-ken suisan shikenjo jigyo hokoku (1931): 16-23. [J,P] Results of 3 exploratory tuna longlining cruises (23 stations) in Ryukyu waters in October-December; fishing logs and plots of station locations; yellowfin, alba- core, and bigeye catch recorded with sur- face and subsurface temperatures and sal- inities, transparencies, on the stations; total catch rates averaged by area. 1934. Investigation of skipjack fishing. Kagoshl- ma-ken suisan shikenjo jigyo hokoku (1932): 1-27. [J,P] Results of 8 exploratory skipjack live-bait fishing cruises in Ryukyu waters from February to June; fishing logs and plot of station locations; water temperature dis- tribution discussed with data on commer- cial landings at local ports. 1935a. Investigation of skipjack fishing. Kagoshi- ma-ken suisan shikenjo jigyo hokoku (1933) : 1-13. [J,P] Results of 9 exploratory skipjack live-bait fishing cruises in Ryukyu waters from March to June; fishing logs and plot of station locations; water temperature dis- tribution discussed with data on commer- cial landings at local ports. 1935b. Cooperative South Seas tuna fishing survey. Kagoshima-ken suisan shikenjo jigyo hokoku (1933) : 15-21. [J,P] Results of 4 combination skipjack live- bait and tuna longlining exploratory cruises in the Sulu and Celebes seas by subsidized commercial vessels; catch rates for total tuna, species not recorded. 1936a. Investigation of skipjack fishing. Kago- shima-ken suisan shikenjo jigyo hokoku (1934):1-16. [J,P] Results of 10 exploratory skipjack live- bait fishing cruises in Ryukyu waters from March to June; discussion of water temperatures and fishing conditions; com- mercial landings at local ports; lengths and weights of 728 skipjack, average con- dition factors of samples. KAGOSHIMA Prefecture Fisheries experiment Station. — Continued 1936b. Cooperative southern skipjack fishing ex- periment. Kagoshima-ken suisan shikenjo jig- yo hokoku (1934) : 17-21. [J,P] Results of 4 exploratory skipjack live-bait fishing cruises in the Sulu and Celebes seas by a subsidized commercial vessel; chart of locations fished; notes on feeding and care of live-bait. 1936c. Investigation of the migration of important fishes. Kagoshima-ken suisan shikenjo jigyo hokoku (1934) :86-87 [J,P] Release records of 45 skipjack tagged on the caudal peduncle in Ryukyu waters. 1937a. Investigation of skipjack fishing. Kago- shima-ken suisan shikenjo jigryo hokoku (1935) 1-8. [J,P] Results of 8 exploratory skipjack live-bait fishing cruises in Ryukyu waters from February to June discussed in relation to surface water temperatures; data on land- ings at local ports by months; average weights, lengths, and condition factors of ten 50-fish samples; distribution of water temperatures and skipjack fishing grounds recorded and plotted for several years; seasonal and annual variations in size composition of the catch; fishing logs and station plots. 1937b. Cooperative southern tuna fishing experi- ment. Kagoshima-ken suisan shikenjo jigyo hokoku (1935) :9-ll. [J,P] Results of 4 combination skipjack live-bait fishing and tuna longline exploratory cruises to the Sulu Sea; skipjack, yellow- fin, and bigeye catches recorded, fishing locations plotted. 1937c. Survey of the present condition of the skip- jack fishing industry. Kagoshima-ken suisan shikenjo jigyo hokoku (1935) : 96-103. [J,P] Numbers of skipjack vessels by size classes in the prefecture, their equipment and operating regime; economic and finan- cial data on the fishery. 1938a. Investigation of skipjack fishing. Kago- shima-ken suisan shikenjo jigyo hokoku (1936) :l-4. [J,P] Results of 9 exploratory skipjack live-bait fishing cruises in Ryukyu waters from February to July; discussion of water tem- perature in relation to fishing conditions; monthly skipjack landings at local ports; average lengths and weights of fifteen 20-fish samples; fishing logs and station plot. BIBLIOGRAPHY ON THE TUNAS 199 KAGOSHIMA PREFECTURE FISHERIES EXPERIMENT Station. — Continued 1938b. Cooperative southern skipjack fishing ex- periment. Kagoshima-ken suisan shikenjo ji- gyohokoku (1936) : 7-10. [J,P] Results of 2 exploratory skipjack fishing cruises in the Celebes and Sulu seas from November to February by a subsidized commercial vessel. 1938c. Investigation of the migration of important fishes. Kagoshima-ken suisan shikenjo jlgyo hokoku (1936) :89. [J,P] Release records for 45 skipjack tagged in Ryukyu waters. 1939a. Investigation of skipjack fishing. Kago- shima-ken suisan shikenjo jigyo hokoku (1937) :l-3. [J,P] Results of 7 exploratory skipjack live-bait fishing cruises in Rjoikyu waters from March to June; fishing logs and plot of stations; average length and weight of 8 samples of approximately 20 fish; month- ly commercial landings at local ports. 1939b. Cooperative southern skipjack fishing ex- periment. Kagoshima-ken suisan shikenjo jigyo hokoku (1937) :7-9. [J,P] Results (not very detailed) of 10 days' exploratory skipjack live-bait fishing in the Sulu Sea by a subsidized commercial vessel; chart of locations fished. 1939c. Investigation of the migration of important fishes. Kagoshima-ken suisan shikenjo jigyo hokoku (1937) :69. [J,P] Relase records of 36 skipjack tagged in Ryukyu waters. 1940a. Experimental skipjack fishing. Kagoshima- ken suisan shikenjo jigyo hokoku (1938) :l-3. [J,P] Results of 9 exploratory skipjack live-bait fishing cruises in Ryukj-u waters from March to July; brief discussion of water temperature and fishing conditions; plot of locations fished; monthly commercial landings at local ports; average lengths and weights of 13 samples of 20 fish each. 1940b. Cooperative southern skipjack fishing ex- periment. Kagoshima-ken suisan shikenjo ji- gyo hokoku (1938) :7-9. [J,P] Results of 4 exploratory skipjack live-bait fishing cruises to the Sulu Sea from Octo- ber to February by a subsidized com- mercial vessel. 1940c. Investigation of the migration of important fishes. Kagoshima-ken suisan shikenjo jigyo hokoku (1938) :43. [J,P] Release records for 20 skipjack tagged in Ryukyu waters. KAGOSHIMA PREFECTURE FISHERIES EXPERIMENT STATION. — Continued 1941a. Investigation of skipjack fishing. Kago- shima-ken suisan shikenjo jigyo hokoku (1939) :l-3. [J,P] Results of 10 exploratory skipjack Uve-bait cruises in Ryukyu waters from March to July; fishing log and station plot; brief discussion of water temperature and fish- ing conditions; average lengths and weights of 8 samples of 20 fish each; monthly commercial landings at local ports. 1941b. Cooperative southern skipjack fishing ex- periment. Kagoshima-ken suisan shikenjo ji- gyo hokoku (1939) :7. [J.P] Fishing logs for 3 exploratory skipjack livebait fishing cruises to the Sulu Sea from October to January by a subsidized commercial vessel. KAKIMOTO, DAIICHI, AKIO KANAZAWA, and KENICHI Kashiwada. 1953. Biochemical studies on skipjack (Katsuwo- nusvagans). IV. Distribution of amino-acid in pyloric caeca. Bull. Jap. Soc. sci. Fish. 19 (6) :729-732. [Je,P] Chemical analysis. Kamimura, Tadao, and MISAO HONMA. 1953. Biology of the big-eyed tuna, Parathunnris mebac;ii(Kishinouye). I. Length frequency of the big-eyed tuna caught in the North Pacific with special reference to biennial frequency. Contrib. Nankai reg. Fish. Res. Lab. 1, Contrib. 46:18 p. [Je,P] Analysis of size composition of bigeye landed by longUnes from 130°E. to 165°W. north of 26°N. from 1948 through 1953; compared for areas and years; discussion of reproduction, growth, and migration. KANAGAWA PREFECTURE FISHERIES EXPERIMENT STATION. 1951a. Report of South Sea tuna fishing experi- ments, 1951. 49 p. [J,P] Detailed results of a longlining cniise to 0°-6°N., 154°-162°E. in January-March: distribution, longline catch rates, relative depth of capture, length frequencies, sex ratios, stomach contents for yellowfin and bigeye tuna. Subsurface water tempera- tures, salinities; notes on plankton. 1951b. Report of work of the Kanagawa Prefecture Fisheries Experiment Station, 1950:1-107. Results of 5 longlining cruises between 5 - 38°N. and 150°-175°E. Yellowfin, bigeye, and albacore catch rates, length frequen- cies, sex ratios, stomach contents (non- quantitative); relative depth of capture; subsurface water temperatures and saU- 200 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE Kanagawa Prefecture fisheries experiment Station. — Continued nities, notes on plankton; fishing logs, N. macropteriis and P. mebachi recorded from stomach contents; shipboard refrig- eration experiments. 1952a. Report of experimental tuna fishing on the eastern grounds by the Sagami Maru. Maguro gyogyo shiken hokoku 4:21 p. [J.P] Report of an exploratory longlining cruise in Feb.-Mar. around 32°N., 171°E. Catch rates of albacore and bigeye; average sizes; length frequency distribution of al- bacore; estimated depth of capture; sex ratios; water temperatures and salinities to 300 m. ; fishing correlated with oceano- graphic conditions. Complete fishing logs. 1952b. Report of experimental tuna fishing on the eastern grounds by the Sagami Maru. Maguro gyogyo shiken hokoku 5:26 p. [J,P] Report of an exploratory longlining cruise in Feb.- Apr. around 30 °N., 175 °E. Alba- core and bigeye catch rates, sex ratios, length frequency distribution; water tem- perature and salinities to 300 m., correla- ted with fishing conditions; catch by branch line number. Complete fishing logs. KANAI, MOTO, and NOBORU KASU. 1938. Report of an investigation of the economics of the Okinawan tuna longline and deep-sea handline fisheries. Okinawa-ken suisan shi- kenjo hokoku 1:1-42. [J,P] History of the fishery, charts of grounds showing expansion, fishing seasons; des- cription and figures of gear and vessels; list of vessels, catch statistics; economics of the fishery: costs of gear, provisions, bait, fuel. Kanamura, Masami, and Kakuji Imaizumi. 1936a. Report of experimental tuna longlining east of Formosa. In Report of experimental fish- ing by the Shonan Maru in 1935. Taiwan s6- tokufu suisan shiken jo shuppan 3:165-202. [J,P] Results of fishing at 21°-23°N., 121°-126° E. in Nov.-Dec. Gear dimensions, station plot, fishing log, weather, surface and subsurface temperature and salinity, transparency, water color; yellowfin, big- I eye: catch rates, depth of capture; body temperature, sex, maturity, length, weight of 25 yellowfin and 3 bigeye; shark dam- age rate; tuna catch and water tempera- ture correlated. 1936b. Fishing conditions for tuna longline boats based at Takao. Taiwan sotokufu suisan shi- kenjo shuppan 3: 203-207. [J,P] Operational data (average cruises per kanamura, Masami, and Kakuji Imaizumi. — Cont. season, Oct. -May, average fishing effort, average catch per cruise by species) for 7 commercial boats fishing the Celebes, Sulu, and S. China Seas; plots by 1° squares of catch rates for yellowfin and bigeye. Kanamura, Masami, and Haruo Yazaki. 1940a. Investigation of tuna longline fishing grounds in the East Philippine Sea. In Report of fishing ground investigations by the Sho- nan Maru in 1937. Taiwan sotokufu suisan shiken jo shuppan 21:1-65. [J,P] Results of exploratory longlining at 3°- 20°N., 123°-131°E. in June-Sept. Fishing log, track chart and station plot; setting, hauling, and soaking time; construction of gear. Subsurface temperatures and salini- ties, transparency, water color at stations. Yellowfin, bigeye, skipjack, albacore catch rates; depth of capture; catch rates plotted against latitude; stomach contents (non- quantitative) ; sex and maturity; body temperature (compared with water tem- perature) ; length, weight, length-weight relation, age according to Aikawa's tables, condition factor; correlation of yellowfin catch with water temperature, salinity, currents, and weather examined; shark damage rates. 1940b. Investigation of tuna longline fishing grounds in the South China Sea. In Report of fishing ground investigations by the Shonan Maru in 1937. Taiwan sotokufu suisan shi- kenjo shuppan 21:67-117. [J,P] Results of exploratory longlining at 16°- 22°N., 116°-121°E. in Feb.-May. Fishing log with operational data, track chart and station plot; gear construction. Subsur- face temperatures and salinity, transpar- ency, water color at stations. Yellovirfin, albacore: catch rates; depth of capture; stomach contents (non-quantitative) ; body temperature, compared with water tem- perature; length, weight, age according to Aikawa's tables, condition factor, sex and maturity; correlation of dark or "green" flesh color with kind of feed, con- dition factor, and sexual maturity at- tempted. Kashiwada, Kenichi, Daiichi Kakimoto, and YOSHISHIGE Horiguchi. 1952. Biochemical studies on skipjack (Katsu- wonus vagaiis). I. Chemical components of pyloric caeca and extractive matter. Bull. Jap. Soc. sci. Fish. 18(4) : 147-150. [Je,P] Fat, moisture, ash, protein content; changes in nitrogen compounds by auto- lysis. BIBLIOGRAPHY ON THE TUNAS 201 KaSHIWADA, KENICHI, DAIICHI KAKIMOTO, and TOSHIMORI Yamasaki. 1953. Biochemical studies on skipjack, m. On the nitrogen compounds in skipjack pyloric caeca extract. Bull. Jap. Soc. sci. Fish 19(1) : 15-18. [J,P] Chemical analysis. KatO, Genji. 1940. An account of longline fishing for tuna. Nanyo suisan joho 4(7) : 8-10. [J.P] General account of a longlining trip in Palau waters: brief notes on yellowfin sex ratio and maturity, on soaking time and bait loss, and on working efficiency of the fishermen. KAWAMURA, HYOzO. 1939. Observations on oceanography and fishing conditions in Palau waters. Nanyo suisan joho 3(1) :2-6. [J,P] General discussion of yellowfin and skip- jack fishing in relation to ocean currents in the Palau area. KAWANA, TAKESHI. 1934. On the relation between the tuna fishery and oceanographic conditions. Hokkaido sui- san shikenjo suisan chosa hokoku 31:80 p. (Spec. sci. Rep.: Fish. U. S. Fish. Wildl. 781. [P] Thunnus orieiitalis, northern Japan: catch statistics; fishing conditions related to temperature, currents, abundance of other fishes, sunspots, lunar period, wind direc- tion; monthly average size of fish in com- mercial landings; tag recovery records for 6 fish. 1935. The tuna spawns in the Japan Sea. Suisan kenkyti shi 30:284-286. Black tuna: spawning. 1937. The catch of tunny, Thunnus orientalis T. and S., off Kushiro, Hokkaido, in relation to the vertical difference in water temperature. Bull. Jap. Soc. sci. Fish. 6(2) :73-74. (Pacific Oceanic Fishery Investigations Translation No. 50. In: Spec. sci. Rep.: U. S. Fish Wildl. 52 . [P] Temperature difference between surface and 50 m., and average numbers of large, medium, and small fish taken per trip in 13 years; Pacific Ocean-northwest. 1938. On tuna fishing conditions at Urakawa. Hoku sui shi sui cho ho 43:125-134. [J] Thuntius orientalis -Jisbing conditions. Pa- cific Ocean - northwest. Kawasaki, Tsuyoshi. 1952. On the populations of the skipjack, Katsuwo- nus pelamis (Linnaeus), migrating to the Northeastern Sea Area along the Pacific Kawasaki, Tsin-osm. — Continued coast of Japan. Bull. Tohoku reg. Fish. Res. Lab. 1:1-14. [Je,P] Populations distinguished by size compo- sition, condition factor, and biting qualties; distribution correlated with oceanographic conditions; length-weight relation; age determination (according to Aikawa's ta- bles) ; Pacific Ocean-northwest. KIDA, Takeo. 1936. On the surface temperature of water in the tunny fishing grounds off Kushiro and Ura- kawa in summer. Bull. Jap. Soc. sci. Fish. 5(2):87-90. [Je,P] Thynnus thynnus: fishing condition cor- related wdth water temperature; size com- position of schools; relation to other fishes, birds, plankton; Pacific Ocean-northwest. KIKAWA, ShOji. 1953. Observations on the spawning of the big- eyed tuna (ParathuH7ius mebachi Kishinouye) near the southern Marshall Islands. Contrib. Nankai reg. Fish. Res. 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Postlarval Neothunnus macropterus, Auxis thazard, and Euthynnus lineatus from the Pa- cific coast of Central America. Fish. Bull., U. S. Fish Wildl. 52(63) :121-127. [P] Observations on spawning seaison; key. Meyer, P. F. 1951. Erfahrungen mit der elektrischen Thunfisch- angel. Fischereiwelt 3(11) :176. Method of using an electrified tuna hook and its effect in stunning tuna. MIE PREFECTURE FISHERIES EXPERIMENT STATION. 1930a. Investigation of skipjack fishing grounds and guidance in fishing. Mie-ken suisan shi- kenjo jigyo hokoku (1927): 1-15. [J,P] Fishing logs; skipjack, bigeye, albacore catches recorded with surface water tem- perature and specific gravity, Japanese waters. 1930b. Skipjack fishing and oceanographic condi- tions. Mie-ken suisan shikenjo hokoku ( 1927 ) : 15-17. [J,P] Skipjack fishing conditions discussed in relation to water temperature and specific gravity; Japanese waters, May-August; plots of two 100-mile oceanographic sec- tions. 1930c. Investigation of tuna fishing grounds and guidance in fishing. Mie-ken suisan shikenjo jigyo hokoku (1927) : 18-33. [J,P] Longline fishing logs and station plots, Japanese waters; albacore, bigeye, black tuna, yellowfin catches recorded with sur- face water temperature and specific grav- ity; plots of two 100-mile oceanographic sections; fishing discussed in relation to oceanographic conditions. 1930d. Investigation of skipjack fishing grounds and guidance in fishing. Mie-ken suisan shi- kenjo jigyo hokoku (1928) :1-18. [J,P] Livebait fishing logs and station plots, Japanese waters; skipjack, albacore, big- eye, yellowfin catches recorded ■5\ith sur- face water temperature and specific grav- ity; plots of two 100-mile oceanographic sections; fishing discussed in relation to oceanographic conditions. 1930e. Investigation of tuna fishing grounds and guidance in fishing. Mie-ken suisan shikenjo jigyo hokoku (1928) : 19-33. [J,P] Longline fishing logs and station plots, Japanese waters; albacore, bigeye, black tuna, yellowfin catches recorded with sur- face water temperature and specific grav- ity; plots of two 100-mile oceanographic 206 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE MiE Prefecture Fisheries Experiment Station. — Continued sections; fishing discussed in relation to oceanographic conditions. 1950a. No. 1 Taiyo Maru's 2nd exploratory tuna fishing cruise in 1950. Mie sui shi jih6 165:8- 12. [J] Fishing conditions; Pacific Ocean - north- west. 1950b. Shinro Maru's investigation of the coastal tuna longline fishery. Mie sui shi jih5 165: 15-16. [J] Fishing conditions; Pacific Ocean — north- west. 1950c. Outline of the skipjack fishery in 1950. Mie sui shi jiho 165:24-25. [J] Fishing conditions; Pacific Ocean — ^north- west. MiGlTA, M., and K. Arakawa. 1948. Melanophorhonnone of fishes. Contrib. cent. Fish. Sta. Japan (1946-48) 39:241-244. [Je] Frigate mackerel, skipjack, Thunnus ori- entalis, yellowfin tuna: melanophorhor- mone content of pituitary glands tabula- ted; proportional weight of various pEirts of T. orientalia brain; brain of yellowfin figured. MiLiC, N. 1937. Tunolov. Ribarski kalendar: 53-57. Fishing methods and gear, Adriatic Sea. MINE., TATSUZ6, and Satoru Iehisa. 1940. Homogeneity of the groups of black tuna in the Satsunan Sea area. Bull. Jap. Soc. sci. Fish. 8(6) : 292-294. (Pacific Oceanic Fishery Investigations Translation No. 53. In: Spec, sci. Rep: Fish. U. S. Fish WUdl. 52). [P] Size composition of conuuerclal longline catch, seasonal changes; age composition (by Aikawa's tables) ; seasonal changes in catch per trip; southern Japan. MIURA, T. 1941. Fishes of South Seas. Tokyo, Unebi Book Co., Ltd. 416 p. [J] Narrative of trip through various fishing grounds (skipjack, etc.). Includes: (1) In search of skipjack, p. 3-32; (2) South Sea skipjack, p. 35-66; (3) Bait for South Sea skipjack, p. 67-72; (4) South Sea Neothun- nus macropterus, p. 73-87. MIYAMA, YOSHIMICHI, and I. OSAKABE. 1938. On the character of the fats obtained from the various bodily parts of fishes. Bull. Jap. Soc. sci. Fish. 7(2) :105-106. [Je.P] Katsuwonus vagans, Parathunnus aibi, Thunnus orientalis: chemical analysis of fats. MiYAMAj YOSHIMICHI, and I. OSAKABE. — Continued 1940. Note on the vitamin oil contained in the liver of fishes. BuU. Jap. Soc. sci. Fish. 9(1) : 16-20. [Je,P] Bigeye, black tuna, skipjack, yellowfin: chemical analysis of liver and liver oil. MIYAMA, YOSHIMICHI, K. Saruya, and T. Hasegawa. 1939. On the characters of the fats obtained from various body parts of fish. Bull. Jap. Soc. sci. Fish. 8(4): 185-186. [ Je,P] Thunnus macropterus: South Seas; chemi- cal analysis of various body parts; length- weight data, sex, and stomach contents of specimens recorded. MiYAZAKi Prefecture High-Seas Fishery Guidance Center. 1953. Tuna longline fishery guidance. Miyazakl- ken enyo gyogo shidosho gyOmu gaiyo: 3-41. [J,P] Reports of 7 longlining cruises to South China Sea, Philippine, and New Guinea waters; complete fishing logs and opera- tional information; catch rates, size com- position, sex ratios and maturity for yel- lowfin and bigeye; water temperature at surface, 50 m., and 100 m. MIZUSHIMA^ KOichirO, et al. 1951. Studies on green meat in albacore. In: Itsumi sho tosen rombvm : 1-81. Publ. by Shi- zuoka kanzume kyokai gijutsubu. [J,P] Green discoloration of albacore flesh stu- died from physiological, histological, chemical, and technological points of view to determine its cause. Molteno, C. J. 1948. The South African tunas. Cape Town, South African Fishing Industry Research Institute, 34 p. [P] Economics of the tuna fishing industry; how to recognize a tuna; commercial tuna . , fishing methods; synonymy, description, •"C' distribution, utilization of Thunnus thyn- nus L., Germo albacora (Lowe), Sarda sarda (Bloch), Euthynnus pelamis L., Euthynnus alletteratus (Rafinesque), Ger- mo alalunga (Bonnaterre), Auxis thazard (Lac^pSde), Germo obesus (Lowe), Neo- thunnus itosibi (Jordan and Evermann). Mooke, Harvey L. 1951a. Estimation of age and growth of yellowfin tuna (Neothunnus macropterus Temminck and Schlegel) in Hawaiian waters. (Unpublished thesis submitted for the degree of Master of Science, University of Hawaii, Honolulu). [P] Scale and vertebra reading, and weight frequency analysis. BIBLJOGRAPHY ON THE TUNAS 207 Moore, Harvey L. — Continued 1951b. Estimation of age and growth of yellow- fin tuna (Neothunnus macropterus) in Ha- waiian waters by size frequencies. Fish. Bull., U. S. Fish Wildl. 52(65) : 133-149. [P] Scale and vertebra reading, and weight frequency analysis. MORiCE, Jean 1953a. Essai syst^matique sur les families des Cybiidae, Thunnidae, et Katsuwonidae, pois- sons scombroides. Rev. Trav. Inst. sci. tech. P6ches marit. 18(l):35-63. [P] Discussion of anatomy and systematics of the genera Acanthocybiuvi, Cybium, Grammatorcynus, Sarda, Orcynopsis, Gymnosarda, Thunnus, Germo, Parathyn- nus, Neothunnus, Katsutvojius, Euthynnus, and Auxis; keys to the genera; brief biblio- graphies; figures of A. solandri. C. ma- culatum, C. regale. C. cavalla, S. sarda, S. orientalis, G.alalonga, K. pelamis, E. aUet- teratus, and A. thazard. 1953b. Un caractfere syst^matique pouvant servir k s^parer les espfeces de Thunnidae atlantiques. Rev. Trav. Inst. sci. tech. Pgches marit. 18 (l):65-74. [P] Descriptions and figures of livers of T. thynnus, G. alalonga, P. obesus, Neothun- nus albacora, and S. sarda; liver morph- ology as a systematic character. MOEOVIC, DINKO. 1950. Prilog bibliografiji jadranskog rlbarstva. Split, Jugoslavia, Institut Oceanograflju i Rib- arstvo u Splitu, 142 p. [P] Bibliography of material on Adriatic (and other) fisheries published in the Croatian language from 1869 to 1949. Morrow, James e. 1954. Data on dolphin, yellowfin tuna, and little tuna from East Africa. Copeia 1954 (1) :14- 16. Morphometric measurements and sex of 11 Euthynnus af finis and 29 Thunnus alba- cora from the Mombasa area. MOWBRAY, LOUIS L. 1935. Description of the Bermuda large-eyed tuna, Parathunnu^ ambigutis, n. sp. Government Aquarium, Bermuda. (Three-page, imnum- bered, privately printed pamphlet.) MURAYAMA, BiNZO, and ShirO OKtmA. 1950. A study of experimental AmericEin-style purse seining (III). J. Fish. Res. Inst. 3:233- 257. [J,P] Catches of purse seiners fishing skipjack and black tuna off the Japanese coast; construction details of a 50-ton purse seiner. MURAYAMA, BiNZO, and ShirO Okura. — Continued 1952. A study of experimental American-style purse seining (IV). J. Fish. Res. Inst. 4:381- 394. [J,P] Catches and details of operations of purse seiners fishing for skipjack and black tuna off the Japanese coast; details of seine construction. Murphy, Garth, I., and E. L. Niska. 1953. Experimental tuna purse seining in the cen- tral Pacific. Comm. Fish. Rev. U. S. Fish Wildl. 15(4) :1-12. [P] Description of gear, results of purse sein- ing in vicinity of Phoenix, Line and Ha- waiian islands; factors affecting success: weather, clarity of water, vertical thermal structure, behavior of surface schools of skipjack and yellowfin; use of livebait in skipjack purse seining. Murphy, Garth I., and Richard S. Shomxhia. 1952. New tuna source : Fish and Wildlife Service's investigation reveals potential new grounds. Pan-Amer. Fish. 6(10): 14-16. [P] Results of experimental longlining in equatorial waters between 150° and 165° W. Yellowfin, bigeye, albacore, skipjack catches, total catch rates, geographical distribution; relation of upwelling to tuna abundance; possibility of commercial ex- ploitation. 1953a. Longline fishing for deep-swimming timas in the central Pacific, 1950-51. Spec. sci. Rep: Fish. U. S. Fish Wildl. 98:47 p. [P] Description of longline fishing; horizontal and vertical distribution of deep-swimming tunas in equatorial waters; sex ratios and size composition of yellowfin, bigeye, al- bacore, skipjack; relation of upwelling to zooplankton and tuna abundance; com- mercial possibilities. 1953b. Longline fishing for deep-swimming tunas in the central Pacific, January-June 1951. Spec. sci. Rep: Fish. U. S. Fish. Wildl. 108:32 p. [P] Results of experimental longlining in equa- torial waters from 120°W. to 180°. Ver- tical and horizontal distribution of yellow- fin, bigeye, albacore, skipjack; size com- positions and sex ratios. Operational data and comparison of gear with shallow and deep float lines. Effect of -wind on up- welling and tuna abundance. Murray, J. J. 1952. Report on 1951 exploratory blue-fin tuna fishing in the Gulf of Maine. Comm. F^sh. Rev. 14(3) : 1-19. [P] Results of experimental purse seining; de- scription of equipment tmd methods; log of operations. 208 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE Nakamura, Hiroshi. 1935. tjber intersexualitat bei Katsuwonus pelamis (Linn.) Trans. Nat. Hist. Soc. Formosa 25 (141) :197-198. [J] Example of hermaphroditism recorded and described. 1936. On the food habits of yellowfin tuna, Neo- thunnus macropterus (Schlegel), from the Celebes Sea. Trans. Nat. Hist. Soc. Formosa 26(148) :l-8. (Pacific Oceanic Fishery Inves- tigations Translation No. 17. In: Spec. sci. Rept: Fish. U. S. Fish Wildl. 23). [P] Analyses of stomach contents of 57 long- line-caught fish; length -weight data. 1938. Preliminary report on the habits of the black tuna, Thumius orientalis (Schlegel). Zool. Mag. 50(5) : 279-281. [J,P] Description and figure of mature egg; gonads figured, distribution, sexual ma- turity, spawning areas and seasons. 1939a. Summary of an investigation of scombroids of Formosan waters. Taiwan suisan zasshi 288:22-26. [J,P] N. macropterus, T. orientalis, P. mebachi, T. germo, K. pelamis, Euthynnus yaito, Kishinoella rara, Gymnosarda nuda, Auxis hira, A. maru: listed as occurring in For- mosan waters; Japanese common names. 1939b. Report on the investigation of Thunnidae in Formosan waters. Taiwan sotokufu suisan shikenjo shuppan 13 : 1-15. [Je,P] Auxis hira, A. maru, Euthynnus yaito: classification; Japanese common names; synonymy. Katstiioonus pelamis, Kishin- oella rara, N. macropterus, Parathunnus mebachi, Thumius germo, T. orientalis: classification; description; distribution; synonymy; Japanese common names; fig- ures of all except N. macropterus, P. me- bachi, and T. germo. N. macropterus: spawning, morphometric data; compared externally with N. itosibi and Semathun- nus guildi. K. rara compared externally with K. zacalles; spawning of T. orientalis. 1939c. Notes on differences between Neothunnus ma- cropterus and Neothunnus itosibi. Taiwan suisan zasshi 288:27-32. [J,P] N. macropterus : classification, morpho- metric data, synonymy; Neothunnus com- pared with 8em,athunnus. 1941. On the body temperatures of some species of Thunnidae and Istiophoridae. Suisan gakkwai ho 8(3) :256-263. [J,P] Yellowfin tuna, bigeye tuna, Formosan and Philippine waters; body temperatures compared with water temperatures at pre- sumed depth of capture. Nakamura, Hiroshi. — Continued 1943. Tunas and spearfishes. Kaiyo no kagaku 3 (10) : 445-459. (Pacific Oceanic Fishery In- vestigations Translation No. 47). [P] Neothunnus macropterus, N. rarus, Para- thunnus mebachi, Thunnus germo, T. ori- entalis: classification, distribution, food, Japanese common names, spawning. 1949. The tunas and their fisheries. Tokyo, Take- uchi Shobo. 118 p. (Translated as Spec. sci. Rep: Fish. U. S. Fish Wildl. 82.) [P] Thunnus orientalis, Germ,o germo, Para- thunnus mebachi, Neothunnus macrop- terus, N. varus : anatomy, description, fig- ures, classification, keys; general account of food, spawning, growth, migration, dis- tribution of longline catch rates in western Pacific; fisheries, relation of fishing grounds to topography and oceanography, fishing seasons; bibliography. Similar ma- terial on spearfishes. 1951. Tuna longline fishery and fishing grounds. Tokyo, Takashima Shoten pub. 144 p. (Also published as Nankai Regional Fisheries Re- search Laboratory Rept. No. 1. Translated as Spec. sci. Rep: Fish. U. S. Wildl. 112) [P] Compilation of research vessel longline catch rates for approximately 20 prewar years. Geographical and seasonal distri- bution of N. macropterus, P. sibi, G. ger- mo, T. orientalis, and spearfishes in the western Pacific and Indonesian waters; average catch rates for each species plot- ted by 1° squares. Relation of fishing grounds and seasons to meteorological and oceanographical phenomena. Nakamura, Hiroshi, tadao kamimura, and YOichi YABUTA. 1953. Size composition of the albacore and bigeyed tuna caught in the North Pacific area. Con- trib. Nankai reg. Fish. Res. Lab. 1, Contrib. 12:6 p. [Je,P] Length composition of longline-caught albacore and bigeye from the central North Pacific; discussion of age and growth, and of annual variations in size composition. Nakayama, TakuzO. 1948. Calculation of the cost price in the tuna fishery. Suisankai 770:10-16. (In: Spec. sci. Rep: Fish: U. S. Fish Wildl. 79). [P] Japanese tuna longline fishery; economic statistics. Nankai Regional fisheries Research Laboratory. 1951a. Report No. 1. 144 p. [J,P] See Nakamura, Hiroshi, 1951. Contents are identical, but this Report has the text and the charts bound separately. BIBLIOGRAPHY ON THE TXINAS 209 Nankai Regional fisheries research laboratory. — Continued 1951b. Supplementary report no. 1:194 p. [J,P] Distribution of albacore longline catch rates in the northwest Pacific by 1° squares, 1948-51; albacore length frequen- cies by month and area; survey of con- struction and dimensions of longline gear of numerous vessels, with area of employ- ment and catch rates by species. Navarro, Francisco de p., and F. lozano. 1950. Carta de pesca de la costa del Sahara, desde el Cabo Juby al Cabo Barbas. Trab. Inst. esp. OceanogT. 21:24 p. [P] Atun (Thiouuis thynnus L.), patudo (Parathunnus obesus Lowe), rabil (Neo- thiuums albacora Lowe), bonito de altura {Katsuwomis pelamys L.), bonito del norte [Germo alalunga Gmelin), melva (Auxis thazard Lacep.) : occurrence and fishing methods. Navaz, Jose M. 1950. Contrlbuci6n al estudio de los esc6mbridos de la costa vasca (atiin, bonitos, y melva). Bol. Inst. esp. Oceanogr. 31:21 p. [P] Morphometries, fishing seasons, catch of Thunnus tliynniis, Germo alalunga, Katsu- womis pelamis, and Auxis thazard in the Bay of Biscay; bibliography; Spanish and Basque names. Nichols, John t., and F. R. La Monte. 1941. Yellowfin, Allison's, and related tunas. Ichth. Contr. Int. Game Fish Assn. 1(3) : 27-32 [P] Neothunniis albacora, N. allisoni, N. cata- linae, N. rarus: classification, description, English common names, key, synonymy. Provisional subspecies: Neothunnus alba- cora macropterus, N. allisoni allisoni, N. allisoni itosibi, and N. rarus zacalles, pro- posed. NiGRELLi, Ross F., and H. W. Stunkard. 1947. Studies on the genus Hirudinella, giant tre- matodes of scombriform fishes. Zoologica, N. Y., 31(4) :185-196. (Contribution No. 747, Dept. of Tropical Research, N. Y. Zoological Society). Table 4: Hirudinella from scombriform fishes other than Acanthocybium: Para- thunniis atlanticus, Katsutconus pelayjiis, Euthynnus alletteratus, Neothunnus ma- cropterus, Thunnus thynnics. Lists name of collector, host, locality and figure. Nishikawa, Sadaichi. 1934. On the future of the high-seas skipjack and tuna fisheries and standards for their opera- ting methods. Rakusui 29(4) : 20-22. [J] • Fishing methods and gear. NiSKA, EDWIN L. 1953. Construction details of tuna long-line gear used by Pacific Oceanic Fishery Investiga- tions. Comm. Fish. Rev. U. S. Fish Wildl. 15(6) :l-6. Also Separate No. 351. [P] Description of gear construction. NnVA, HITOMARO. 1937. On the pigments in the muscles of fishes. Rep. No. 1, Pigments of tuna muscle. Suisan kenkyu shi 32(6) :306-313. [J] Chemical analysis. NOGUCHI, SADAMI. 1938. The Ogasawara Is., and the future of our tuna fishery. Suisankai 666:44-46. [J] Pacific Ocean - northwest. Nomura, ToshizO, et al. 1952-3. Survey of the high-seas tuna fisheries based on landings at Misaki, Tokyo, and Yaizu. Reports of the following months' operations are in the indicated numbers of the Kanagawa suishi geppo: April and May 1952, 1:3-20; June 1952, 2:1-7; July 1952, 3:1-6; Aug. 1952, 4:1-10; Sept. 1952, 5:1-8; Oct. and Nov. 1952, 6:1-10; Dec. 1952 and Jan. 1953, 7:1-15; April 1953, 9:1-10; June 1953, 11:1-20; July 1953. 12:1-18; the reports of February and March 1953 operations were published as Maguro-rui mizuagechi chosa (imnumbered, undated) by the Kanagawa Prefecture Fishesies Experi- ment Station; the report for May 1953 opera- tions is in Report of survey for tuna fishing 1:1-22; the report for August 1953 operations is in Tuna fishing 4 : 17-32. [ J,P] Average catch rates for yellowfin, big- eye, albacore, bluefin, skipjack, and spear- fishes reported by Japanese longline ves- sels from various areas of the western and central Pacific, Indonesian waters, and the Indian Ocean by months; plots of lo- cations fished by the vessels investigated; discussion of fishing conditions in each area for the month; length frequencies of each species by area. oiTA Prefecture fisheries experiment St.ation. 1930. Report of experimental tuna fishing in the Kanto region (1927). oita-ken suisan shiken- j6 jigyo hokoku (1927-28) :l-40. [J,P] Longline catches of yellowfin, bigeye, and black tuna off central Japan : morphome- tric data, body temperatures compared with water temperatures; gear construc- tion, general account of tuna fisheries and bases of the region. OKADA, YAICHIRO, and KlY0M.\TSU MATSUBARA. 1938. Keys to fishes and fish-like animals of Japan. Tokyo, Sanseido Co., Ltd., p. 146-150. [J] Axixis hira, A. tapeinosoma, Euthynnus alletteratus, E. yaito, Germo germo, Kat- 210 FISHERY BULLETIN OP THE FISH AND WILDLIFE SERVICE Okada, Yaichiro, and Kiyomatsu Matsubara. — Con- tinued suwomis vagans, Kishinoella rata, Neo- thunnus itosibi, N. macropterus, Parathun- nus orientalis: classification, description, key, Japanese common names. 1953. Bibliography of fishes in Japan (1612-1950). Mie Prefecture, Faculty of Fisheries, Prefec- tural University of Mie, 228 p. [P] General bibliography of Japanese and foreign literature on fishes which occur in Japanese waters; arranged by years, not annotated. Okada, YaichirO, et al. 1935. Illustrated atlas of Japanese fishes. Tokyo, The Sanseido Co., Ltd. Scomber tapeinocephalus, Auxis tapeino- soma, Sarda oi-ientalis, Katsuwonus va- gans, Euthynnus yaito, Thunnus orientalis, Germo germo, Parathunnus sibi, Neothun- nus macropterus. All figured, briefly de- scribed, brief notes on distribution, habits and utilization; spawning. OKAJIMA, KIYOSHI. 1939. Tuna fisheries of Kanagawa and Shizuoka prefectures. Nanyo suisan joho 3(1) :7-23. [J.P] General description of ports of Misaki and Omaezaki; accounts of vessels, gear, fish- ing methods, fishing grounds, and sample catches of longline, livebait, and mother- ship-type handlining fisheries. Okamoto, GorozO. 1940. On the composition of shoals of "katsuo," Euthynnus vagans (Lesson), in the north- eastern Japanese waters as analyzed by the body weight. Bull. Jap. Soc. sci. Fish. 9(3) : 100-102. (Pacific Oceanic Fishery Investiga- tions Translation No. 52. In: Spec. sci. Rep.: Fish. U. S. Fish Wildl. 51) . [P] Size composition of commercial catch from various groimds, seasonal changes; age (according to Aikawa's tables). Okinawa prefecture fisheries experiment Station. 1931. Investigation of the maturity of skipjack. Okinawa-ken suisan shikenjo jigyo hokoku (1930:106-107. [J,P] Skipjack length-weight data; gonad weight and maturity. 1936a. Experimental skipjack fishing. Okinawa-ken suisan shikenjo jigryo hokoku (1934) :l-28. [J,P] Results of livebait fishing in Ryukyu waters ;fishing logs of 15 trips, with opera- tional data, catch, weather, surface tem- perature. Okinawa Prefecture fisheries experiment Station. — Continued 1936b. Experimental longline fishing for tuna. Okin- awa-ken suisan shikenjo jigyo hokoku (1934) : 29-35. [J,P] Results of two cruises to Philippines and Hainan I. waters; construction of gear; fishing logs with catch, weather, surface temperature, operational data; yellowfin, bigeye: catch per imit of effort. 1936c. Experiment on holding livebait for skipjack. Okinawa-ken suisan shikenjo jigyo hokoku (1934) :36-46. [J,P] Attempt to correlate captures of gatsun {Trachurus sp.) with air and water tem- perature, atmospheric pressure, specific gravity of water. 1940a. Experimental skipjack fishing. Okinawa-ken suisan shikenjo jigyo hokoku (1939) :3-5. [J,P] Ryukjru Islands: skipjack catch recorded with air and water temperature. 1940b. Experimental tuna fishing. Okinawa-ken suisan shikenjo jigyo hokoku (1939) :6-8. [J,P] Bigeye tuna, black tima: Bonin Islands; catches recorded with water temperature. 1943. Elxperimental skipjack fishing. Okinawa- ken suisan shikenjo jigyo hokoku (1941) :4-14. [J,P] Ryiikyu Islands: distribution of skipjack; catch recorded with air and water tem- peratures. OKUMA, YASUMICHI, ET AL. 1935. Investigation of South Sea fisheries by the Shonan Maru; investigation of tuna fishing grounds. Taiwan sotokufu suisan shikenjo jigyo hokoku (1933) :120-123. [J,P] Yellowfin tuna: Indo-Pacific region; dis- tribution, stomach contents, length-weight data, sexual maturity, fishing conditions in relation to oceanography and weather, catch per unit of effort. OKUMURA, ISABURO. 1943. Management of the southern tuna fisheries. Suisankai 728:67-72. [J] OMORi, Kageyu, and T. Fujimoto. 1940. Experimental longline fishing for tuna. Na- gasaki-ken suisan shikenjo jigyo hokoku (1938) :175-214. [J,P] Bigeye tuna, black tuna: Japan; catches in relation to water temperature and spe- cific gravity. OMORI, KAGEYU, and M. Fukuda. 1938. Experimental longline fishing for tuna. Na- gasaki-ken suisan shikenjo jigyo hokoku (1936) : 47-48. [J,P] BIBLIOGRAPHY ON THE TUNAS 211 OMORI, KAGETi'U, and M. FUKUDA. — Continued Bigeye tuna, black tuna: Japan; catches in relation to water temperature and spe- cific gravity. 1940. Experimental longline fishing for tuna. Na- gasaki-ken suisan shikenjo jigyo hokoku (1937):45-92. [J,P] Bigeye tuna, black tuna: Japan; catches in relation to water temperature and spe- cific gravity. Onodera, Matsuji. 1941. The relation of freshness and condition fac- tor of Palau Islands skipjack to the ratio of finished products. Nanyo suisan joho 5(2): 7-17. [J,P] Skipjack leng^-weight data, body con- dition of fish. OYA, Takeo, and T. Takahashi. 1936. On the growth acceleration substance in the liver of the marine animals. Bull. Jap. Soc. sci. Fish. 5(3) :192-194. [Je,P] Growth hormones in skipjack livers. Partlo, J. M. 1950. A report on the 1949 albacore fishery (Thun- nus alalunga) . Circ. Pac. biol. Sta., Nanaimo 20:37 p. [P] Thumtus alalunga: age and growth, catch in relation to water temperature, tagging, food, fishing gear. 1951. A report on the 1950 albacore fishery of Brit- ish Columbia {Thunnus alalunga). Circ. Fac. biol. Sta., Nanaimo 23:7 p. [P] Thunnus alalunga: distribution of catch for temperature intervals, tagging, size groups in commercial catch, offshore water temperatures, log records. Phillipps, W. J. 1932. Notes on new fishes from New Zealand. N. Z. J. Sci. Tech. 13(4) :226-234. Description of Pacific yellow-finned alba- core, Neothunmis itosibi, as new to N. Z. PoissoN, R., and E. Postel. 1951. Sur la presence d'une vessie natatoire chez certains individus d'Euthynmis alliteratus (Rafn.) (poisson t616ost6en). C. R. Acad. Sci. Paris 233:201-203. Anatomy of air bladder; description. POSTEL, E. 1949. Les thonidds d'Afrique Occidentale Francaise. Bull. Serv. £lev. Industr. anim. A. O. F. 2(4) : 39-46. 1950. Pfiche sur les cfltes d'Afrique occidentale. n. Rapport et note sur quelques poissons de surface de la presqu'ile de Cap-Vert. Inspec- tion g6n6rale de I'^levage, Dakar, French West Africa. 77 p. [P] Postel, E. — Continued Euthynnus alletteratus : morphology, ana- tomy, ecology; fishing methods. Powell, a. w. b. 1937. Marine fishes new to New Zealand; includ- ing the description of a new species of Halie- utaea. Trans, roy. Soc. N. Z. 67(1) :80. Neothunnus itosibi: recorded, synonymy, description, figured. POWELL, Donald E. 1950. Preliminary report on 1950 North Pacific albacore tuna explorations of the John N. Cobb. Comm. Fish. Rev. 12(12) : 1-7. [P] Results of exploratory trolling, gillnetting, and longlining, Oregon to Alaska; water temperatures related to fishing; stomach contents, tagging, plankton; size range of catch. Powell, Donald e., and H. A. Hildebrand. 1950. Albacore tuna exploration in Alaskan and adjacent waters, 1949. Fish. Leafl., U. S. Fish Wildl., 376:33 p. [P] HUstory of West Coast fishery; abundance and location as shown by exploratory surface and deep trolling catches; water temperatures related to fishing; length composition of catch, stomach contents (non-quantitative) ; potential livebait sources evaluated; plankton, saury, blue shark, birds, cetaceans as indicators of tuna. Powell, Donald E., D. L. Al\'erson, and R. Living- stone, JR. 1952. North Pacific albacore tuna exploration-1950. Fish. Leafl., U. S. Fish Wildl., 402:56 p. 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Sta. oc^anogr. Sal- ammbo 15:1-19. Bluefin tuna; migrations related to pH of sea water. RIVAS, LUIS R. 1951. A preliminary review of the western North Atlantic fishes of the family Scombridae. Bull, mar. Sci. Gulf Caribb. 1(3) :209-230. [P] Key :Auxis thcuzard, Katsuwonus pelamis, Euthynnus alletteratus, Thunnus thynnus, Thunnus atlanticus, Thunnus argentivit- tatus, Thunnus alalunga, Sarda sarda. 1953. The pineal apparatus of tunas and related scombrid fishes as a possible light receptor controlling phototactic movements. Bull. mar. Sci. Gulf Caribb. 3(3) : 168-180. [P] Thunnus thynnus, Germo, Parathunnus, Neothunnus, Auxis, Katsuwonus, Euthyn- nus, Sarda: anatomy; photo taxis. Robins, J. P. 1952. Further observations on the distribution of striped tuna, Katsuwonus pelamis L., in east- ern Australian waters, and its relation to sur- face temperature. Aust. J. Mar. Freshw. Res. 3(2):101-110. [P] ROEDEL, Phil M. 1948a. Common marine fishes of California. Fish. 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Twent. Cent. 28(112) : 634-649. Chart showing distribution, where caught by hooks and where by nets; habits; de- scriptions of madrague or thonnaire (nets BIBLIOGRAPHY ON THE TUNAS 213 RUSSELL, F. S. — Continued used in Mediterranean and on coasts of Spain, Portugal, and Africa). 1936. Submarine illumination in relation to ani- mal life. Rapp. Cons. Explor. Mer Copen- hague 101(2) :l-8. [P] Thiouius thymius: effect of illumination on migration. S.\itO, Munek.\zu. 1937. Oceanographic investigations and tuna fish- ing conditions in the Solomon Islands. Suisan kenkyu shi 32(5) :260-271. [J] Oceanographic conditions in relation to fishing; Pacific Ocean-southwest. Sakai, MorisabukO, and Michio Uno. 1940. Tuna (maguro) fisheries and boats in Japan. J. Imp. Fish. Exp. Sta. 10:1-37. [Je,P] Statistical study of 80 Japanese tuna long- line boats : equipment, fishing gear, crews, finances, fishing seasons and groimds. Samson, v. J. 1940. Notes on the occurrence of albacore Germo alalunga in the North Pacific. Copeia 1940 (4):271. Distributional note. Sanzo, L. 1932. Uova e primi stadi larvali di tonne (Orcy- nus thynmis Ltkn.). Mem. R. Com. Talass. Ital. 189:16 p. [P] Spawning season in Mediterranean de- duced from egg and larva collections; de- scription and figures of mature ovarian eggs and pelagic eggs; compared with eggs of T. germo and Auxis; development, measurements, description, and figures of larvae at various stages. 1933. Uova e primi stadi larvali di alalonga (Or- cynus germo Ltkn.). Mem. R. Com. Talass. Ital. 198:9 p. Spawning season in the Mediterranean deduced from collections of eggs and lar- vae; descriptions and figures of mature eggs and developing embryos and larvae. Sasaki, takeo. 1932. A consideration of albacore fishing condi- tions and oceanographic conditions north of Zunan. Rakusui 27(6) :9-ll. 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Spawning of Pacific tunas and its implica- tions to the welfare of the Pacific tuna fish- eries. Trans. N. Amer. Wildl. Conf. 13:366- 371. [P] Auxis sp., Euthynnus Uneatus, E. yaxto, Katsuwonus pelamis, Neothunnus viacrop- terus, Thunnus germo: Pacific Ocean, dis- tribution; review of records and observa- tions on spawning and juveniles; manage- ment problem. 1951. Some recent advances in the study of the biology and racial division of Pacific tunas. Proc. Indo-Pacif. Fish. Coun. 2(2/3) :63-69. [P] Neothunnus macropterus, Thunnus germo, 214 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE SCHAEFERj MiLNEE B. — Continued Katsuwonus pelamis, Parathunnus sibi, Thunnus thxmnina, Euthynnus lineatus, Auxis thMzard: general review of work on age and growth, morphometries and racial studies, size composition, spawning. 1952. Comparison of yellowfin tuna of Hawaiian waters and of the American west coast. Fish. Bull., U. S. 52(72) :353-373. 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Prime indagini sul valore quantitativo delle concentrazioni gamiche del tonno {Thunnus thynnus L.) Boll. Zool. agr. Bachic. 14(1/3): 93-103. Thunnus thynnus: age, spawning; Medi- teiranesm Sea. Seale, Alxtn. 1940. Report on fishes from Allan Hancock Ex- peditions in the California Academy of Sciences. A. Hancock Pacif. Exped. 9(1) : 17-18. [P] Euthynnus lineatus, Katsuwoniis pelamis, Neothunnus macropterus : descriptions, records of capture; Mexico to Galapagos. Sexla, M. 1930. Distribution and migrations of the tuna (Thunnus thynnus L.) studied by the method of hooks and other observations. Int. Rev. Hydrobiol. 24 : 446-466. See (SeUal952). ' 1931. The tuna (Thunnus thynnus L.) of the western Atlantic. An appeal to fishermen for the collection of hooks found in tuna fish. Int. Rev. Hydrobiol. 25(1/2) :46-47. [P] Thunnus thynnus L. compared with T. J secundodoTsalis Storer; harpooning of tuna; distribution in western Atlantic, mi- grations. 1932. Studio sul tonno. 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[P] Auxis thazard, Euthynnus alletteratus, Katsuwonus pelamis, Kishinoella tonggol, Neothunnus macropterus, Thunnus germo, T. maccoyi: distribution, description, key, figures, Australian common names, size groups, migration and spawning of T. maccoyi; length-weight relationship and internal and external differences of K. tonggol and T. maccoyi compared; livers of K. tonggol and T. m,accoyi figured. Serveinty, D. L. — Continued 1941b. Victorian tunas and some recent records. Vict. Nat., Melb. 58:51-55. Southern bluefin (T. maccoyii) , albacore (T. germo), yeUowfin (Neothunnus m/i- cropterus), striped tuna (Katsuwonus pelamis), bonito (Sarda australis) : re- corded; description of N. macropterus. 1942a. Notes on the economics of the northern tuna (Kishinoella tonggol). J. Coun. scl. ind. Res. Aust. 15(2) : 94-100. Distribution, feeding habits, stomach con- tents, spawning. 1942b. The tuna Kishinoella tonggol Bleeker in Australia. J. Coun. sci. ind. Res. Aust. 15(2) : 101-112. Distribution, description, ratios of various body proportions, internal anatomy, syn- onymy; compared with K. zacalles, Neo- thunnus rarus, Thunnus tiicolsoni, Thynnus tonggol; figures of T. tonggol and K. tonggol, cranium of K. tonggol figured. 1947. A report on commercial tuna trolling tests in southeastern Australia. J. Coun. sci. ind. Res. Aust. 20(1): 1-16. Katsuwonus pelamis, Thunnus germ,o, T. maccoyi: catch per unit of effort; size composition of T. maccoyi. 1948. Allothunnus faUai, a new genus and species of tuna from New Zealand. Rec. Canterbury (N. Z.) Mus. 5(3) :131-135. Classification, description, morphometries; internal anatomy of type specimen; records of specimens and occurrences; compared with Katsuwonidae. Sette, Oscar E. 1954. Progress in Pacific Oceanic Fishery Inves- tigations 1950-53. Spec. sci. Rep: Fish. U. S. Fish Wildl. 116:75 p. [P] Brief summary of POFI tuna research In the central Pacific. Yellowfin: catch per unit of effort, fishing conditions in rela- tion to area; size composition; spawning; growth; distribution of larvae; morpho- metries, definition of populations. Skip- jack: distribution, fishing conditions in relation to season and oceanog:raphic fea- tures. Fishing methods: results of troll- ing, gillnetting, purse seining, livebfiit fishing, longlinlng. Shapiro, Sidney. 1948a. Aquatic resources of the Ryukjoi area. SCAP Nat. Resour. Sect. Rep. 117:54 p. Also Fish. Leaf!., U. S. Fish Wildl., Wash. 333. [P] Auxis hira, A. tapeinosoma, E. yaito, Kat- suwonus pelamis, Neothunnus macrop- terus, Parathunnus sibi, Thunnus germo. 216 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE Shapiro, Sidney. — Continued T. orientalis: bibliography, distribution, Ryukyuan common names, migration, spawning of K. pelaniis. 1948b. The Japanese tuna fisheries. SCAP Nat. Resour. Sect. Rep. 104:60 p. 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Euthynnus lineatus, Germo alalunga, Kat- suwonus pelamis, Neothunnus macrop- terus, Thunnus thynnus: description, dis- tribution, food, spawning, key, English common names, figures. Auxis thazard: description, distribution, English common names, figure, key. Migration of G. ala- lunga, K. pelamis, and N. macropterus. N. macropterus compared with Allison's tuna. Wakfel, H. E. 1950. Outlook for development of a tuna industry in the Philippines. Res. Rep. U. S. Fish. Wildl., 28:37 p. [P] History of Philippine tuna fishery; recent exploration for tuna (live bait fishing ex- periments, longline trawl experiments, trolling experiments, traps). Descriptions of Neothunnus macropterus, Katsuwonus pelamis, Euthynnus yaito, Auxis tlutzard, Grammatorcynus bicarinatus, Gymnosar- da nuda, Sarda orientalis. For each species mentioned: distribution, figure, and de- scription. Watanabe, Hajime. 1939. Investigation of albacore. Shizuoka-ken suisan shikenjo jigyo hokoku (1936-38) 1939: 22-23. [J,P] Albacore: mid-Pacific; stomach contents, sexual maturity, body proportions of males and females compared, morphome- tric data, probable spawning season, area, number of eggs. Watanabe, Haruo. 1940. Fishing conditions south of the Marshall Islands. Nanyo suisan 58, March 25, 1940; No. 59, April 25, 1940; No. 60, May 25, 1940. (Pacific Oceanic Fishery Investigations Trans- lation No. 11. In: Spec. sci. Rep.: Fish. U. S. Fish Wildl. 43). [P] Narrative report of an exploratory long- line fishing cruise from Jaluit to the Solo- mons and back. Some oceanographic in- formation and lengths and weights of the fish taken. Bigeye tuna, yellowfin tuna. Watanabe, Nobuo. 1941. Measurements on the bodily density, body temperature and swimming-velocity of "Katu- wo," Euthynnus vagans (Lesson). Bull. Jap. Soc. sci. Fish. 11(4) :146-148. [J,P] Body volume and weight for three speci- mens, temperature immediately after cap- ture for 10, and swimming speeds of 10 as timed from a fishing boat; body tem- peratures compared with water tempera- tures. J BIBLIOGRAPHY ON THE TXnSTAS 223 Welsh, James P. 1949a. A preliminary study of food and feeding habits of Hawaiian kavvakawa, mahimahi, ono, aku, and ahi. Fish. Progr. Rep. 1(2) :26 p. [P] Quantitative analyses of stomach contents of Euthynnus yaito, Neothiinnus macrop- terus, and Katsuwonus pelamis from Hawaiian waters; food organisms listed, numbers and volumes given for each. 1949b. Range extension of the file fish Monocan- thus Dielanocephalus. Pacif. Sci. 3(1) :100. [P] Hawaii: specimens recovered from Eu- thynnus yaito. 1949c. A trolling survey of Hawaiian waters. Fish. Res. Progr. Rep. 1(4) : 30 p. [P] Trolling catch per unit of effort for Euthynnus yaito, Neothunnus macrop- terus, and Kaisuw&jius pelamis; fishing areas and lures compared. Westman, J. R., and P. W. Gilbert. 1941. Notes on age determination and growth of the Atlantic bluefin tuna, Thunnus thynnus L. Copeia 1941:70-72. Thunnus thynnus: scale reading, age- length relationship; measurements taken from 100 tuna off Long Island in 1938. Westman, James R., and Willlam c. Neville. 1942. The tuna fishery of Long Island. New York, Board of Supervisors, Nassau County. 30 pp. Thunnus thynnus: scale reading, age- fishing methods described — trolling, hand- lining; catch per unit of effort; lengrth frequency; length-weight relationship; age and growth; scale reading, maturity, tagging; Atlantic. Whitehead, S. S. 1930. California bluefin tima. Calif. Fish Game 16(3) : 231-233. Thunnus thynnus: distribution. 1931. Fishing methods for the bluefin tuna (.Thunnus thynnus) and an analysis of the catches. Fish. Bull. Sacramento 33:32 p. [P] Classification, distribution, figure, migra- tion, spawning, catch per unit of effort. Whitley, Gilbert P. 1937. The Middleton and Elizabeth Reefs, South Pacific Ocean. Aust. Zool. 8(4) :229-231. Wanderer wallisi proposed as new genus and species; synonymy, description, food; compared with E. yaito and E. allettera- tus. 1947. New sharks and fishes from Western Australia. Aust. Zool. 11(2) : 129-150. Whitley, Gilbert P. — Continued Euthynnus alletteratus, Katsuwonus pela- mis, Kishinoella tonggol, Neothunnus ma- cropterus, Thunnus maccoyi: recorded, Australian common names. Wilson, Robert C. 1953. Tuna marking, a progress report. Calif. Fish Game 39(4) : 429-442. [P] History of tagging of tuna, present tag- ging methods, tag application methods. Figures of various types of tags. WoLi-E Murray, D. K. 1932. Tunny (Thunmis thynnus L.) in the North Sea. J. Cons. int. Explor. Mer 7(2) : 251-254. [P] Some observations made by the author during his voyages as to occurrence, habits, and food of T. thynnus. A table is given showing the first and last ap- pearances in the seasons of 1923-31. YABE, HIROSHI. 1953. Juveniles collected from South Seas by Tenyo Maru at her second tuna research voy- age (preliminary report). Contrib. Nankal reg. Fish. Res. Lab. 1, Contrib. 25:14 p. [J,P] Surface trawl and night-light collections in the Carolines area include 2 Katsu- loonus pelamis and 4 unidentified scom- briform larvae; description, measure- ments, and figure of a 5.2-mm. Katsu- wonus pelamis. Yabe, Hiroshi, Noboru Anraku, and Tokumi mori. 1953. Scombroid youngs found in the coastal seas of Aburatsu, Kyushu, in summer. Contrib. Nankai reg. Fish. Res. Lab. 1, Contrib. 11 :10 p. [J,P] Young Katsuivonus pelamis, Euthynnus yaito, Auxis tapeinosoma, TMmnus orien- talis, Neothunnus macropterus, Sarda orientalis, and Auxis hira taken by various gear in coastal waters; fishing conditions correlated with oceanography; habits, food, size composition, morphometries. Yabe, Hiroshi, and Tokumi Mori. 1948. Report of skipjack investigations for 1947. Cent. Fish. Exp. Sta. Rep. 30. [P] Ryukyu Islands: length -weight data, stomach contents, catch correlated with water temperature; maturity of gonads, age analysis, spawning season, estimated number of eggs, past records of Juveniles captured. 1950. An observation on the habit of bonito, Katsuwonus vagans, and yellowfin, Neothun- nus macropterus, school under the drifting timber on the surface of ocean. Bull. Jap. Soc. sci. Fish. 16(2):35-39. [Je.P] 224 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE YABE, HiROSHi, and TOKUMI MORI. — Continued Katsuwonus pelamis, Neothiinnus macrop- terus: ecologry; live-bait fishing; yellowfin length frequencies. Yabuta, YOichi. 1953. On the stomach contents of the tuna and marlin from the adjacent seas of Bonin Islands. Contrib. Nankai reg. Fish. Lab. 1, Contrib. 15:6 p. [J,P] Lists and gives numbers of organisms found in 76 longline-caught albacore, big- eye, and yellowfin tuna stomachs (no volumes); describes food organisms; dis- cusses seasonal differences in stomach contents, relation to oceanographic condi- tions; young skipjack as food. Yabuta, YOichi and Shoji ueyanagi. 1953a. The distributions of tunas in the equatorial region. I. Contrib. Nankai reg. Fish. Res. Lab. 1, Contrib. 28:8 p. [Je,P] Distribution and migration of yellowfin, bigeye, and black marlin in southern Mar- shalls area as shown by longline catch rates of mothership fleet; seasonal changes in size composition of yellowfin; fishing conditions correlated with oceano- graphic conditions. 1953b. The distribution of tunas in the equatorial region. II. Hooked-rate of yellowfin tuna. Contrib. Nankai reg. Fish. Res. Lab. 1, Con- trib. 29:6 p. [J,P] Longline catch rates of yellowfin tuna from mothership fleet operations in south- em Carolines waters related to locality, hydrography, time, and size composition. Yamamoto,, Shigeo. 1933. Points of information for the skipjack fish- Yamamoto, Shigeo. — Continued ery gained from the study of fish's eyes. Rakusui 28(11) : 927-930. [J] Skipjack: anatomy. 1934. Points of information for the skipjack fish- ery gained from the study of fish's eyes. Rigakkai 32(1):28. [J] Skipjack: anatomy. YAMAMOTOj Shokichi. 1940. Views on increasing the commercial value of dried fish sticks from the South Seas. Nanyo suisan 3(11) : 21-35. [J,P] Skipjack: Japan, Formosa, South Seas; proportional weights of various body parts. yamanakAj Ichiro. 1950. On the size composition of skipjack in the Northeastern Sea area. Nippon kaiyogakkai Shi 5(214). [J] Yonezavva, Matsunosuke. 1950. Skipjack fishing experiences. Kaiyo no kagaku 6(1) :47-49. [J] Skipjack, Japanese waters. Yoshihara, Tomokichi. 1951-52. Distribution of fishes caught by the long- line. I. Horizontal distribution. II. Vertical distribution. III. Determination of the swim- ming depth. Bull. Jap. Soc. sci. Fish. 16(8) : 367-369; 16(8) :370-374; 18(5) :187-190. [Je,P] Statistical study comparing catch rates on different parts of longline sets; rela- tive swimming depths of Germo germo, Parathunnus sibi, and spearfishes deduced from estimated depths of hooks on which captured. Zei, M. 1948. zivot naseg Jadrana. 220 p. Tuna, Adriatic Sea. INDEX BY SUBJECTS Adriatic Sea Fortunie, 1930. Hadzi, 1934. Hirtz, 1933. Mili6, 1937. Morovie, 1950. Scordia, 1939b. soljan, 1930. Vitlov, 1949. Zei, 1948. Age Brock, 1943. Conseil International pour 1' Exploration de la Mer, 1933. Heldt, 1950. Higashi, 1941. Ikebe, 1939a, 1939b, 1940a, 1940b, 1940c, 1941a, 1941b. Kanamura and Yazaki, 1940a, 1940b. Kawasaki, 1952. Kimura, 1935, 1941, 1942a. LeGall, 1949. Lozano, 1950. Mine and lehisa, 1940. Moore, 1951a, 1951b. Nakamura, Kamimura, and Yabuta, 1953. Partlo, 1950. Sasaki, 1939b. Schaefer, 1948b, 1951 Scordia, 1943. Sella, 1952. Uno, 1936a, 1936b. Westman and Gilbert, 1941. Westman and Neville, 1942. Aku. See Katsuwonus. Albacore. See Germo. Allison's tuna. See Neothunnus itosibi. AUothunnus Fraser-Brunner, 1950. Serventy, 1948. Anatomy Berg, 1947. Chabanaud, 1930. Conrad, 1937. Eckles, 1949. 1 . Frade, 1930a, 1930b, 1931. Frade and DeBuen, 1932. Godsil and Byers, 1944. Greenbood, 1952. Higashi, 1941b. Imamura, 1949. Kafuku, 1950. LeGall, 1949. Letaconnoux, 1950. Nakamura, 1935, 1949. Anatomy — Continued Poisson and Postel, 1951. Priol, 1944. Rivas, 1953. Roedel, 1948a. Schaefer and Marr, 1948a. Serventy, 1941a, 1942b, 1948. Shimada, 1954. Sueyhiro, 1936, 1938, 1941, 1942, 1950. Uchihashi, 1953. Yamamoto, 1933, 1934. As food of tunas Asano, 1939. Marukawa, 1939b. Suda, 1953. Yabuta, 1953. Atlantic Ocean Alaejos, 1931. Beebe, 1936. Beebe and Tee-Van, 1936. BelWn and Bardan de BellOn, 1949. Bigelow and Schroeder, 1953. Bini, 1931. Bouxin and Legendre, 1936. Carlson, 1951. Chilton, 1949. Crane, 1936. DeBuen, 1930, 1931, 1932, 1935, 1937. Ehrenbaum, 1934. Farina, 1931. Ferreira, 1932. Frade, 1930, 1931a, 1931b, 1937. Godsil and Holmberg, 1950. Heldt, 1931, 1932a, 1932b. LeDanois, 1933, 1938, 1951. LeGall, 1934a, 1934b, 1934c, 1934d, 1949. Legendre, 1932, 1933, 1934, 1937, 1940. Letaconnoux, 1950. Lozano, 1950. Mather, 1954. Molteno, 1948. Morice, 1953b. Mowbray, 1935. Murray, 1952. Navarro and Lozano, 1950. Navaz, 1950. Postel, 1949, 1950. Priol, 1944. Rivas, 1951, 1953. Russell, F. S., 1934b. Schaefer and Walford, 1950. Schuck, 1951. Schuck and Mather, 1951. Schultz, 1949. Sella, 1930. 225- 226 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE Atlantic Ocean — Continued Westman and Gilbert, 1941. Westman and Neville, 1942. Australian waters Robins, 1952. Serventy, 1941a, 1941b, 1942a, 1942b, 1947, 1948. Auocis Asano, 1939. Bamhart, 1936. Brock, 1949. Chu, 1931. DeBeaufort and Chapman, 1951. DeBuen, 1930, 1932, 1935. Domantay, 1940. Fish, 1948. Fisheries Society of Japan, 1931. Food and Agr. Organ., U. N., 1949b. Fowler, 1936, 1938, 1944, 1949. Graham, 1938. Herald, 1951. Herre, 1940, 1943. Herre and Umali, 1948. Imamura, 1949. Joubin, 1934. LeGall, 1934a. Marukawa, 1939b. Mead, 1951. Molteno, 1948. Morice, 1953a. Nakamura, 1939a, 1939b. Navarro and Lozano, 1950. Navaz, 1950. Okada and Matsubara, 1938. Rivas, 1951, 1953. Sanzo, 1932. Schaefer, 1948c, 1951. Schaef er and Marr, 1948a. Serventy, 1941a. Shapiro, 1948a. Soldatov and Lindberg, 1930. Tanaka, 1931. Taranetz, 1937. Tester, 1952. Tinker, 1944. Tominaga, 1943. Uchihashi, 1953. Wade, 1949, 1951. Walford, 1937. Warfel, 1950. Yabe et al., 1953. Aiixis hira Imamura, 1949. Nakamura, 1939b. Okada and Matsubara, 1938. Shapiro, 1948a. Soldatov and Lindberg, 1930. Tanaka, 1931. Taranetz, 1937. Yabe et al., 1953. Auxis inaru Imamura, 1949. Nakamura, 1939a, 1939b. Soldatov and Lindberg, 1930. Taranetz, 1937. Auxis tapeinosoma Okada and Matsubara, 1938. Okada et al., 1935. Shapiro, 1948a. Uchihashi, 1953. Wade, 1949. Yabe et al., 1953. Auxis thasard Bamhart, 1936. Brock, 1949. DeBeaufort and Chapman, 1951. DeBuen, 1930, 1932, 1935. Domantay, 1940. Fish, 1948. Fisheries Society of Japan, 1931. Food and Agr. Organ., U. N., 1949b. Fowler, 1936, 1938, 1944, 1949. Fraser-Brunner, 1950. Graham, 1938. Herald, 1951. Herre, 1940. Herre and Umali, 1948. Joubin, 1934. LeGall, 1934a. Marukawa, 1939b. Mead, 1951. Molteno, 1948. Morice, 1953a. Navarro and Lozano, 1950. Navaz, 1950. Rivas, 1951. Schaefer, 1951. Schaefer and Marr, 1948a. Serventy, 1941a. Tester, 1952. Tinker, 1944. Wade, 1949. Walford, 1937. Warfel, 1950. Baltic Sea Ros^n, 1943. Behavior Anonymous, 1953b. Bigelow and Schroeder, 1953. Hiatt and Brock, 1948. Imamura, 1949. Kida, 1936. Kimura, Iwashita, and Hattori, 1952. LUling, 1952a. Murphy and Niska, 1953. Nakamura, 1949. Russell, F. S. 1934b, 1936. Schaefer, 1948b. Serventy, 1942a. BIBLIOGRAPHY ON THE TUNAS 227 Behavior — Continued Tanaka, 1935. Tester, 1952. Tester et al., 1952. Tominaga, 1943. Uda, 1940c. Uda and Tsukushi, 1934. Watanabe, 1941. Yabe and Mori, 1950. Yoshihara, 1951, 1952. Bibliography Bini, 1952. Corwin, 1930. Heldt, 1930, 1931, 1932, 1934. LeGall, 1949. Legendre, 1934. Morovie, 1950. Nakamura, 1949. Navaz, 1950. Okada and Matsubara, 1953. Rosa, 1950. Shapiro, 1948a. Shimada, 1951a. Bigeye tuna. See Parathunnus spp. Black tuna. See Thunnus orientalis. Blackfin tuna. See Parathunnus atlanticits. Bluefin tuna. See Thunntts thynnus. Body condition Aikawa and Kato, 1938. Ikebe and Matsumoto, 1937. Kanamura and Yazaki, 1940a, 1940b. Kawasaki, 1952. Mizushima et al., 1951. Morice, 1953a. Onodera, 1941. Schweigger, 1949. South Seas Gov't., 1941c. Suyehiro, 1936. Body temperature Kanamura and Imaizumi, 1936a. Kanamura and Yazaki, 1940a, 1940b. Nakamura, 1941. oita Pref . Fish. Expt. Sta., 1930. Scagel, 1949. Society for the Promotion . . . 1936. Uda, 1941. Watanabe, N., 1941. Bonito. See Katsuwonus pelamis. Caribbean Sea LeDanois, 1951. Rawlings, 1953. Catch per unit of effort Bates, 1950. Chiba Pref. Fish. Expt. Sta., Katsuura Br., 1938, 1941. Formosa Gov't.-Gen. Fish. Expt. Sta., 1933. Heldt, 1930, 1932. Hiratsuka and Imaizumi, 1934. Hiratsuka and Ito, 1934. Catch per unit of effort — Continued Ikebe, 1940, 1941, 1942. Imaizumi, 1937. Inoue, 1953. Jap. Bur. Fish., 1939, 1940. Kanagawa Pref. Fish. Expt. Sta. 1951b. Kanamura and Imaizumi, 1936a. Kanamura and Yazaki, 1940a, 1940b. Kimura, 1942a. Marukawa, 1939c. Mine and lehisa, 1940. Murphy and Shomura, 1953b. Nakamura, 1949. Nomura et al., 1952-3. Okinawa Pref. Fish. Expt. Sta., 1936b. Okuma et al., 1935. Serventy, 1947. Sette, 1954. Tester, 1952. Van Campen, 1952. Westman and Neville, 1942. Whitehead, 1931. Yabuta and Ueyanagi, 1953. Chemical analysis Asaka, Noguchi, and Mimoto, 1953. Dontcheff and Legendre, 1938. Higashi and Hirai, 1948. Horiguchi, Kakimoto, and Kashiwada, 1950. Horiguichi, Kashiwada, and Kakimoto, 1953. Kakimoto, Kanazawa, and Kashiwada, 1953. Kashiwada, Kakimoto, and Horiguchi, 1952. Kashiwada, Kakimoto, and Yamasaki, 1953. Kodama, lizuka, and Harada, 1934. Maldura, 1946. Matsui, K., 1942b. Migita and Arakawa, 1948. Miyama and Osfikabe, 1938, 1940. Miyama, Saruya, and Hasegawa, 1939. Mizushima et al., 1951. Niwa, 1937. 6ya and Takahashi, 1936. Shimizu, 1947. Tomiyama, T., 1933. Tomiyama, Y., et al., 1941. Classification Berg, 1947. DeBuen and Frade, 1932. Dieuzeide, 1930. Frade and DeBuen, 1932. Fraser-Brunner, 1949, 1950. Godsil and Byers, 1944. Herre, 1953. Nakamura, 1939b, 1939c, 1943, 1949. Nichols and LaMonte, 1941. Okada and Matsubara, 1938. Roedel, 1948a. Serventy, 1948. Shapiro, 1948b. Soldatov and Lindberg, 1930. Taranetz, 1937. 228 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE Classification — Continued Wade, 1949. Walford, 1931. Whitehead, 1931. Color, water. See Oceanographic conditions. Common names Ancieta C, 1952. Bamhart, 1936. Chevey, 1932. DeBuen, 1930. Delsman and Hardenburg, 1934. Fish, 1948. Food and Agr. Organ. U. N., 1949b. Ikebe and Matsumoto, 1938. LeGall, 1949. Marukawa, 1939a. Nakamura, 1939b, 1943. Navaz, 1950. Nichols and LaMonte, 1941. Okada and Matsubara, 1938. Roedel, 1948a. Rosa, 1950. Schultz, 1949. Serventy, 1941a. Shapiro, 1948a, 1948b. Smith, 1947. Tinker, 1944. Tominaga, 1943. Walford, 1931, 1937. Whitley, 1947. Condition, body. See Body condition. Contents, stomach. See Food. Currents. See Oceanographic conditions. Description Ancieta C, 1952. Barnard, 1948. Bamhart, 1936. Beebe and Tee-Van, 1936. Bigelow and Schroeder, 1953. Boeseman, 1947. Brock, 1949. Chabanaud, 1930. Chevey, 1932. Chilton, 1949. Clemens and Wilby, 1946. Crane, 1936. DeBeaufort and Chapman, 1951. DeBuen, 1932. Delsman and Hardenburg, 1934. Eckles, 1949. Fish, 1948. Fisheries Society of Japan, 1931. Fowler, 1933, 1936, 1938. Frade, 1931. Fraser-Brunner, 1950. Godsil and Byers, 1944. Graham, 1938. Heldt, 1931, 1932. Hildebrand, 1946. Description — Continued Ikebe and Matsumoto, 1938. Imamura, 1949. Joubin, 1934. June, 1952b. Kanamura and Yazaki, 1940a. LeGall, 1934a, 1934b, 1934c, 1934d. Marukawa, 1939a, 1939c. Molteno, 1948. Mowbray, 1935. Nakamura, 1939b, 1949. Nichols and LaMonte, 1941. Okada sind Matsubara, 1938. Okada et al., 1935. Poisson and Postel, 1951. Powell, A. W. B., 1937. Roedel, 1948a. Schaefer and Marr, 1948a, 1948b. Schweigger, 1943. Seale, 1940. Serventy, 1941a, 1941b, 1942b, 1948. Shapiro, 1948b. Soldatov and Lindberg, 1930. Tinker, 1944. Wade, 1949, 1950a. Walford, 1931, 1937. Whitley, 1937. Distribution Ancieta C, 1952. Anonymous, 1941b, 1953a, 1953b. Bahr, 1952. Bamhart, 1936. Bigelow and Schroeder, 1953. Bini, 1952. Brock, 1939. Carlson, 1951. Chapman, 1946. Chevey, 1932a, 1932b. Chu, 1931. Clemens and Wilby, 1946. Cowan, 1938. DeBuen, 1930. Delsman, 1933. Delsman and Hardenburg, 1934. Fish, 1948. Fitch, 1953. Food and Agr. Orgsui. U. N., 1949a, 1949b. Formosa Gov't.-Gen. Fish. Expt. Sta., 1933. Fowler, 1938, 1944. Fraser-Brunner, 1949, 1950. Godsil, 1949. Godsil and Greenhood, 1948. Hasegawa, 1937. Heldt, 1931a, 1931b, 1932. Herre, 1932, 1933, 1935, 1936, 1940 Hildebrand, 1946. Hiratsuka and Imaizumi, 1934. Hiratsuka and Ito, 1934. Imamura, 1949. Isawa, 1935. BIBLIOGRAPHY ON THE TUNAS 229 Distribution — Continued Jap. Bur. Fish., 1940. Joubin, 1934. Kanamura and Yazaki, 1940a, 1940b. Kimura, 1941, 1942b. Kumata, 1941. LeDanois, 1933, 1938. LeGall, 1934b, 1934c, 1934d. Leterdre, 1937. Maidura, 1946. Martin, 1938. Mather, 1954. Molteno, 1948. Murphy and Shomura, ^953a, 1953b. Nakamura, 1939b, 1943. 1949, 1951. Navarro and Lozano, 1950. Okada and Matsubara, 1938. Okada et al., 1935. Okinawa Pref. Fish. Expt. Sta., 1943. 6kuma et al., 1935. Powell, D., 1950. Powell and Hildebrand, 1950. Powell et al., 1952. Robins, 1952. Roedel, 1948a, 1948b. Rosa, 1950. Royce, 1953. Russell, F. S., 1933a, 1933b, 1934b. Samson, 1940. Schaefer, 1948c. Schuck and Mather, 1951. Schultz and DeLacy, 1936. Schweigger, 1943, 1949. Sella, 1930. Serventy, 1941a, 1942a, 1942b, 1948. Sette, 1954. Shapiro, 1948a, 1948b. Shimada, 1954. Smith and Schaefer, 1949. Soldatov and Lindberg, 1930. South Seas Gov't. . . . 1937a, 1937b, 1941a. Tanaka, 1931. Taranetz, 1937. Tinker, 1944. Uda, 1935a. Wade, 1949. Walford, 1937. Whitehead, 1930, 1931. Wolfe Murray, 1932. Yabuta and Ueyanag:!, 1953. Ecology (other than oceanog:raphic conditions or food) DeBeaufort and Chapman, 1951. Lozano, 1950. Marukawa, 1939a. Nakamura, 1949. Powell, D. E., 1950. Powell and Hildebrand, 1950. Powell et al., 1952. Priol, 1944. Ecology — Continued Uchihashi, 1953. Yabe and Mori, 1950. Eggs DeJong, 1940. Delsman, 1931. Delsman and Hardenburg, 1934. Hatai et al., 1941. Kikawa, 1953. Marr, 1948. Nakamura, 1938. Sanzo, 1932, 1933. Watanabe, Hajime, 1939. Yabe and Mori, 1948. Euthynnus Bigelow and Schroeder, 1953. Boeseman, 1947. Bonham, 1946. Brock, 1949. Carlson, 1951. Chabanaud, 1930. Chapman, 1946. Chevey, 1932a, 1932b, 1934. Chiba Pref. Fish. Expt. Sta., 1936. Chilton, 1949. Conrad, 1937. DeBeaufort and Chapman, 1951. DeBuen, 1930, 1935. DeJong, 1940. Delsman, 1931. Delsman and Hardenburg, 1934. Domantay, 1940. Dung and Royce, 1953. Eckles, 1949. Fish, 1948. Fisheries Society of Japan, 1931. Fitch, 1953. Food and Agri. Organ. U. N., 1949b. Fowler, 1931, 1938, 1944, 1949. Frade, 1932. Fraser-Brunner, 1949, 1950. Fukuda and lizuka, 1940. Godsil and Greenhood, 1948. Hatai et al., 1941. Herald, 1949. Herre, 1932, 1933, 1940. Herre and Umali, 1948. Hiatt and Brock, 1948. Higashi, 1940. Hildebrand, 1946. Imamura, 1949. Joubin, 1934. Kagoshima Pref. Fish. Expt. Sta., 1930c. LeGall, 1934b. Maidura, 1946. Mather, 1954. Mead, 1951. Mie Pref. Fish. Expt. Sta., 1930c, 1930e. Molteno, 1948. Morice, 1953a. 230 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE Euthynnus — Continued Morrow, 1954. Nakamura, 1939a, 1939b. Nigrelli and Stunkard, 1947. Okada and Matsubara, 1938. Okada et al., 1935. Poisson and Postel, 1951. Postel, 1950. Rivas, 1951, 1953. Roedel, 1948b. Ronquillo, 1953. Schaefer, 1948c, 1951. Schmidt, 1930. Schmitt and Schultz, 1940. Schuck, 1951. Scale, 1940. Serventy, 1941a. Shapiro, 1948a. Smith and Schaefer, 1949. Tanaka, 1931. Tester, 1952. Tester et al., 1952. Tinker, 1944. Tominaga, 1943. Tubb, 1948. Van Cleave, 1940. Wade, 1950a, 1950b, 1951. Walford, 1937. Warfel, 1950. Welsh, 1949a, 1949b. Whitley, 1937, 1947. Yabe, et al., 1953. Euthynnus af finis. See also E. cUletteratus. Dung and Royce, 1953. Fraser-Bnmner, 1949. Euthynnus alleterata. See E. alletteratus. Euthynnus alleteratu^. See E. alletteratus. Euthynnus alletteratus Bigelow and Schroder, 1953. Boeseman, 1947. Carlson, 1951. Chabanaud, 1930. Chapman, 1946. Chilton, 1949. DeBeaufort and Chapman, 1951. DeBuen, 1930, 1935. DeJong, 1940. Delsman, 1931. Delsman and Hardenburg, 1934. Food and Agr. Organ. U. N., 1949b. Fowler, 1931. Frade, 1932. Herre, 1932, 1940. Hildebrand, 1946. Joubin, 1934. LeGall, 1934b. Maldura, 1946. Manter, 1940. i ;."■ -■- Mather, 1954. ■^• Molteno, 1948. Euthynnus alletteratus — Continued Morice, 1953a. Nigrelli and Stunkard, 1947. Okada and Matsubara, 1938. Poisson and Postel, 1951. Postel, 1950. Rivas, 1951. Schmidt, 1930. Schmitt and Schultz, 1940. Schuck, 1951. Serventy, 1941a. Smith and Schaefer, 1949. Tanaka, 1931. Tinker, 1944. Van Cleave, 1940. Whitley, 1937, 1947. Euthynnus allitteratus. See E. alletteratus. Euthynnus lineatus Fowler, 1938, 1944. Fraser-Brunner, 1949. Mead, 1951. Roedel, 1948b. Schaefer, 1948c, 1951. Seale, 1940. Walford, 1937. Euthynnus pelamis. See Katsuwonus. Euthynnus pelamys. See Katsuwonus. Euthynnus vagans. See Katsuwonus. Euthynnus yaito Bonham, 1946. Brock, 1949. Chabanaud, 1930. Chevey, 1932a, 1932b, 1934. Chiba Pref. Fish. Expt. Sta., 1936. Domantay, 1940. Eckles, 1949. Fisheries Society of Japan, 1931. Fitch, 1953. Fraser-Brunner, 1949. Fukuda and lizuka, 1940. Godsil and Greenhood, 1948. Hatai et al., 1941. Herald, 1949. Herre, 1933, 1940. Herre and Umali, 1948. Hiatt and Brock, 1948. Higashi, 1940. Imamura, 1949. Kagoshima Pref. Fish. Expt. Sta., 1930c. Mie Pref. Fish. Expt. Sta., 1930c, 1930e. Nakamura, 1939a, 1939b. Okada and Matsubara, 1938. Okada et al., 1935. Ronquillo, 1953. Schaefer, 1948c. Shapiro, 1948a. Tester, 1952. Tester et al., 1952. Tominaga, 1943. Wade, 1950a, 1950b, 1951. ■\-:'rK^ bibliography: ON' THE TUNAS T, ■!;?>..;• 201 Suthynntts yaito — Continued Warfel, 1950. Welsh, 1949a, 1949b. WhiUey, 1937. Yabe et al., 1953. Euthymis alletteratus. See Euthynnus allettei-atus. Figures Anonymous, 1938. Barnard, 1948. Barnhart, 1936. Bigelow and Schroeder, 1953. Bini, 1952. Chevey, 1932. DeBuen, 1930. Delsman and Hardenburg, 1934. Eckles, 1949a, 1949b. Fisheries Society of Japan, 1931. > Fowler, 1944. Frade, 1931. Fraser-Brunner, 1949, 1950. Godsil and Byers, 1944. Heldt, 1931a, 1931b, 1932b. Joubin, 1934. LeGall, 1934a, 1934b, 1934c, 1934d, 1949. Morice, 1953a. Nakamura, 1939b, 1949. Okada et al., 1935. Powell, A. W. B., 1937. Schaefer and Marr, 1948a, 1948b. Serventy, 1941a, 1942. Smith, 1935. Smith and Schaefer, 1949. Suyehiro, 1936, 1942. Tinker, 1944. Tominaga, 1943. Wade, 1949. Walford, 1937. Whitehead, 1931. Fishing conditions correlated with area Schweigger, 1949. Fishing conditions correlated with season Clemens and Wilby, 1946. Kimura, 1933, 1942a. Kimura and Ishii, 1933. Lozano, 1950. Mine and lehisa, 1940. Nakamura, 1949. Navaz, 1950. Ros^n, 1943. Schaefers, 1952. Schweigger, 1949. Sette, 1954. Uda and Watanabe, 1938. Wade, 1950a. Walford, 1931. Fishing methods and gear (other than purse seining, longlining, and llvebait) Anonymous, 1937b, 1953b. Bates, 1950. Fishing methods and gear — Continued Bini, 1931, 1933. Carlson, 1951. Cleaver and Shimada, 1950. De La Tourrasse, 1951. Dieuzeide, 1931. Domantay, 1940. Farina, 1931. Ferreira, 1932. Fortunia, 1930. Godsil, 1938. Heldt, 1931a, 1932. Hirtz, 1933. Imamura, 1953. June, 1951b. Kimura, Iwashita, and Hattori, 1952. Kreutzer, 1951a, 1951b. Legendre, 1936. LUling, 1952a. Markukawa, 1939a, 1939c. Matsumoto, W., 1952. Meyer, 1951. Mili(5, 1937. Navarro and Lozano, 1950. Nishikawa, 1934. Postel, 1950. Powell, D. E., 1950. Powell and Hildebrand, 1950. Powell et al., 1952. Rawlings, 1953. Russell, F. S., 1934b. Schaefers, 1952, 1953. Schweigger, 1949. ,.'>;i--: Scordia, 1940. Sella, 1931. Sette, 1954. S" ' goljan, 1930. South Seas Gov't. . . . 1937. Tester, 1952. Thiel, 1938. Van Campen, 1953. Vitlov, 1949. Welsh, 1949c. Westman and Neville, 1942. Yabe et al., 1953. Food Anonymous, 1938. Asano, 1939. Ban, 1941. Beebe, 1936. Bouxin and Legendre, 1936. Carlson, 1951. Chapman, 1946. Clemens and Wilby, 1946. Crane, 1936. Delsman and Hardenburg, 1934. Eckles, 1949. Fitch, 1950. Formosa Gov't.-Gen. Fish. Expt. Sta., 1933. Hart and HoUister, 1947. ^c j 232 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE Food — Continued Hart et al., 1948. Hatai et al., 1941. Heldt, 1934. Herald, 1949. Hildebrand, 1946. Imai, 1950. Imamura, 1949. Iwate Pref. Fish. Expt. Sta., 1953. Jap. Bur. Fish., 1933, 1934, 1935, 1939, 1940. Kanagawa Pref. Fish. Expt. Sta., 1951a. Kiironuma, 1940. LeGall, 1949. Legendre, 1932, 1933, 1934, 1940. Lozano, 1950. McHugh, 1952. Marukawa, 1939b, 1939c. Miyama et al., 1939. Nakamura, 1936, 1943, 1949. okuma et al., 1935. Partlo, 1950. Powell, D. E., 1950. Powell and Hildebrand, 1950. Powell et al., 1952. Priol, 1944. Relntjes, 1952. Reintjes and King, 1953. Ronquillo, 1953. Scagel, 1949. Schaefers, 1952, 1953. Schweigger, 1949. Sella, 1952. Serventy, 1942a. Shapiro, 1948b. Suda, 1953. Suyehiro, 1938. Tominaga, 1943. Uda, 1940a. Walford, 1937. Watanabe, Hajime, 1939. Welsh, 1949a, 1949b. Whitley, 1937. Yabe et al., 1953. Yabe and Mori, 1948. Yabuta, 1953. Germo Aikawa, 1933. Aikawa and Kato, 1938. Alverson and Chenowith, 1951. Anonymous, 1938, 1953a. Arcidiacono, 1935. Asano, 1939. Bamhart, 1936. Belloc, 1935. Bini, 1952. Bouxin and Legendre, 1936. Brock, 1939, 1943, 1949. Chiba Pref. Fish. Expt. Sta., 1936a, 1936b. Chiba Pref. Fish. Expt Sta., Germo — Continued Katsuura Branch, 1937, 1938b, 1941a, 1941b, 1941c, 1941d, 1941e, 1941f. Clemens and Wilby, 1946. Conseil Int'l pour 1' Exploration de la Mer, 1933. Cowan, 1938. DeBuen, 1930, 1935. De La Tourrasse, 1951. Dontcheff and Legendre, 1938. Dung and Royce, 1953. Ferreira, 1932. Fish, 1948. Fisheries Society of Japan, 1931. Food and Agr. Organ. U. N., 1949b. Fowler, 1938, 1944. Frade, 1953. Fraser-Brunner, 1950. Ganssle and Clemens, 1953. Godsil, 1945, 1948, 1949a, 1949b. Godsil and Byers, 1944. Godsil and Greenhood, 1948. Hart and HoUister, 1947. Hart et al., 1948. Hasegawa, 1938. Heldt, 1950. Herre, 1940. Herre and Umali, 1948. Hildebrand, 1946. Ikebe, 1939a, 1940. Inanami. 1942. Inoue, 1953. Iwate Pref. Fish. Expt. Sta., 1953. Jap. Bur. Fish., 1939, 1940, 1942. Joubin, 1934. Kagoshima Pref. Fish. Expt. Sta., 1930b, 1930c, 1931b, 1932c, 1933b. Kanagawa Pref. Fish. Expt. Sta., 1952a, 1952b. Kanamura and Yazaki, 1940, 1940b. Kimura, 1942a, 1942b, 1949. Kimura, Iwaahita and Hattori, 1952. Kuronuma, 1940. LeDanois, 1933, 1938, 1951. LeGall, 1934c, 1949. Legendre, 1932, 1933, 1934, 1936, 1940. Letaconnoux, 1950. Lozano, 1950. McHugh, 1952. Maldura, 1946. Marukawa. 1939c. Mie Pref. Fish. Expt. Sta., 1930c, 1930e. Mizushima et al., 1951. Molteno, 1948. Morice, 1953a, 1953b. Murphy and Shomura, 1953a, 1953b. Nakamura, 1939b, 1949, 1951. Nakamura et al., 1953. Nankai Reg. Fish. Res. Lab., 1951a, 1951b. Navarro and Lozano, 1950. Navaz, 1950. BIBLIOGRAPHY ON THE TUNAS 233 Germo — Continued Okada and Mataubara, 1938. Okada et al., 1935. Partlo, 1950, 1951. Powell, D. E. 1950. Powell and Hildebrand, 1950. Powell et al., 1952. Priol, 1944. Rivas, 1951, 1953. Roedel, 1948a. Samson, 1940. Sanzo, 1932, 1933. Sasaki, 1932, 1939b. Scagel, 1949. Schaefer, 1948c. Schaefers, 1952, 1953. Schultz and DeLacy, 1936. Serventy, 1941a, 1941b, 1947. Shapiro, 1948a, 1948b. Shizuoka Pref . Fish. Expt. Sta. 1937b. Smith, 1947. Society for the Promotion . . . 1936, 1937a. Soldatov and Lindberg, 1930. South Seas Gov't. . . . 1943a. Suyehiro, 1951. >' Takayama and Ando, 1934. Tanaka, 1931. Taranetz, 1937. Tauchi, 1940c. Tinker, 1944. Toyama, Y., et al., 1941. Uda, 1931a, 1935a, 1936b, 1940b. Uda and Tokunaga, 1937. Uno, 1936a, 1936b. Van Campen, 1952. Van Campen and Shimada, 1951. Walford, 1931, 1937. Watanabe, Hajime, 1939. Yabuta, 1953. Yoshihara, 1951-52. Germo alalunga. See Germo. Germo aVbacores. See Neothunntts itosibi, Germo argentivittatus. See Neothunnus argentivittatus. Germo germo. See Germo. Germ.0 germon. See Germo. Germo macropterus. See Neothunnus -macropterus. Germo obesus. See Parathunnus atlanticus. Germo sihi. See Parathunnus sibi. Germon. See Germ^o. Growth Aikawa and Kato, 1938. Brock, 1943. Conseil Int'l pour 1' Exploration de la Mer, 1933. Frade, 1937a, 1937b. Galtsoff, 1952. Heldt, 1930, 1931a, 1943, 1950. Kamimura and Honma, 1953. Kimura, 1932, 1935. Kimura and Ishii, 1932. Matsui, K., 1942b. Growth — Continued Moore, 1951a, 1951b. Nakamura, 1949. Nakamura et al., 1953. Partlo, 1950. Schaefer, 1948b, 1951, 1952. Schaefer emd Walford, 1950. Schweigger, 1949. Sella, 1952. Sette, 1954. Westman and Gilbert, 1941. Westman and Neville, 1942. Gymnosarda Manter, 1940. Nakamura, 1939a. Warfel, 1950. Gymnosarda af finis. See Katsuwonus. Gymnosarda alletterata. See Euthynnus alletteratus. Gymnosarda pelamis. See Katsuwonus. Habits. See Behavior. Honmaguro. See Thunnus orientalia. Indiem Ocetin Molteno, 1948. Morrow, 1954. Nomura et al., 1952-53. Smith, 1935. Indonesian waters Anonymous, 1941b. Japanese Bureau of Fisheries, 1933, 1934, 1935. Kimura, 1942a. Matsubara, 1943. Nakfimura, 1936, 1951. Nomura et al., 1952-53. Okuma et al., 1935. Shimada, 1937. South Seas Gov't. . . . 1941d. Juveniles. See Young. Katsuo. See Katsuwon%is. Katsuwonidae Serventy, 1948. Katsuwonus Abe, 1939. Aikawa, 1933, 1937. Aikawa and Kato, 1938. Anonymous, 1937a, 1937b, 1939a, 1939b, 1941b. Auffret, 1931. Bini, 1952. Blackburn and Rajoier, 1951. Brock, 1949. Chapman, 1946. Chiba Pref. Fish. Expt. Sta., 1936a, 1936b. Chiba Pref. Fish. Expt. Sta., Katsuura Branch, 1937, 1938, 1941c, 1941d. Cleaver and Shimada, 1950. Clemens and Wilby, 1946. DeBuen, 1930, 1935. 234 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE Katsuwonus — Continued Delsman and Hardenburg, 1934. Domantay, 1940. Dung and Royce, 1953. Eckles, 1949a, 1949b. Fish, 1948. Fisheries Society of Japan ,1931. Food and Agr. Organ. U. N., 1949b. Formosa Gov't.-Gen. Fish. Expt. Sta., 1930, 1931, 1932, 1933, 1934. Fowler, 1931, 1934, 1938, 1944, 1949. Fukuda and lizuka, 1940. Godsil, 1936, 1938a, 1938b, 1945, 1949. Godsil and Byers, 1944. Herald, 1951. Herre, 1932, 1933, 1935, 1936, 1940, 1953. Herre and Umali, 1948. Higashi, 1940a, 1940b, 1941, 1942. Higashi and Hirai, 1948. Hildebrand, 1946. Horiguchi, Kakimoto, and Kashiwada, 1950. Horiguchi, Kashiwada, and Kakimoto, 1953. Ikebe, 1938. Ikebe and Matsumoto, 1937, 1938. Ikeda, 1932. Ikeda and Ando, 1933. Inanami, 1942b, 1942c, 1942d. Joubin, 1934. June, 1950b, 1951b. '■•■• ■■-'' Kagoshima Pref. Fish. Expt. Sta., 1930a, 1931a, 1932a, 1933a, 1934, 1935a, 1935b, 1936a, 1936b, 1936c, 1937a, 1937b, 1937c, 1938a, 1938b, 1938c, 1939a, 1939b, 1939c, 1940a, 1940b, 1940c, 1941a, 1941b. Kakimoto, Kanazawa, and Kashiwada, 1953. Kashiwada, Kakimoto, and Horiguchi, 1952. Kashiwada, Kakimoto, and Yamasaki, 1953. Kimura, 1941, 1942b, 1949. Kimura, Iwashita, and Hattori, 1952. Kodama, lizuka, and Harada, 1934. Koyasu, 1931. Kumamoto Pref. Fish. Expt. Sta., 1946. Kumata et al., 1941. Kuronuma et al., 1949. LeGall, 1934d. Maldura, 1946. Manter, 1940. Marr, 1948. Martin, 1938. Marukawa, 1939a, 1939b. Mather, 1954. Matsui, K., 1942a, 1942b. Matsumoto, T., 1937. Matsumoto, W., 1952. Mie Pref. Fish. Expt. Sta., 1930a, 1930b, 1930d, 1950. Migita and Arakawa, 1948. Miura, 1941. Miyama and Osakabe, 1938, 1940. Molteno, 1948. Morice, 1953a. Katsuwonus — Continued Murayama and Okura, 1950, 1952. Murphy and Niska, 1953. Murphy and Shomura, 1953a, 1953b. Nakamura, 1935, 1939a, 1939b. Navarro and Lozano, 1950. Navaz, 1950. Nigrelli and Stunkard, 1947. Nishikawa, 1934. Nomura et al., 1952-53. Okada and Matsubara, 1938. Okada et al., 1935. Okamoto, 1940. Okinawa Pref. Fish. Expt. Sta., 1931, 1936a, 1940a, 1943. Onodera, 1941. oya and Takahashi, 1936. Rawlings, 1953. Rivas, 1951, 1953. Robins, 1952. Roedel, 1948a. Ronquillo, 1953. Sasaki, 1939a. Sasaki and Takehisa, 1932. Schaefer, 1948b, 1948c, 1951. Schaefer and Marr, 1948b. Seale, 1940. Serventy, 1941a, 1941b. Sette, 1954. Shapiro, 1948a, 1948b. Shizuoka Pref. Fish. Expt. Sta., 1936, 1937a. Smith and Schaefer, 1949. Smith, 1947. Soldatov and Lindberg, 1930. South Seas Gov't. . . . 1937a, 1937c, 1938, 1941a, 1941b, 1941c, 1942, 1943b. Suda, 1953. Suyehiro, 1936, 1938, 1941, 1942, 1950. Tachikawa, 1932. Taihoku Prov. Fish. Expt. Sta., 1932. Takayama, 1934. Tanaka, 1931. Taranetz, 1937. Tauchi, 1943. Tester, 1952. Tinker, 1944. Tominaga, 1943. Toyama, Y., et al., 1941. Uda, 1932b, 1933, 1935b, 1935c, 1936a, 1938, 1939, 1940a, 1940b, 1940c, 1941, 1948. Uda and Tsukushi, 1934. Van Campen, 1952. Wade, 1950a, 1950b, 1951. Walford, 1931, 1937. Warfel, 1950. Watanabe, N., 1941. Welsh, 1949a. Whitley, 1947. Yabe, 1953. Yabe and Mori, 1948, 1950. BIBLIOGRAPHY ON THE TtJNAS 235 Katsuwoniis — Continued Yamamoto, S., 1933, 1934. Yamamoto, Shokichi, 1940. Yamanaka, 1950. Yonezawa, 1950. Katsuwcmris pelamis. See Katsuwonus. Keys Brock, 1949. DeBeaufort and Chapman, 1951. DeBuen, 1930. DeBuen and Frade, 1932. Delsman and Hardenburg, 1934. Frade and DeBuen, 1932. Fraser-Brunner, 1949, 1950. Godsil and Byers, 1944. Hildebrand, 1946. Mead, 1951. Morice, 1953a. Nakamura, 1949. Nichols and LaMonte, 1941. Okada and Matsubara, 1938. Rivas, 1951. Roedel, 1948a. Soldatov and Ldndberg, 1930. Taranetz, 1937. Uda, 1933. Wade, 1949. Walford, 1931, 1937. Kihada. See Neothunnua macropterus. Kishinoella Brock, 1949. Dung and Royce, 1953. Fraser-Brunner, 1950. Nakamura, 1939a, 1939b. Soldatov and Lindberg, 1930. Whitley, 1947. Kishinoella rara Brock, 1949. Nakamura, 1939a, 1939b. Kishiyioella tonygol Dung and Royce, 1953. Serventy, 1941a, 1942a, 1942b. Whitley, 1947. Kishinoellu zacalles Serventy, 1942b. Kuromaguro. See Thunnus orientalis. Larvae. See Young. Laws and regulations Anonymous, 1952. Cerquetelli, 1936. Sugiura, 1932. Length-weight data. See Morphometries. Length-weight relationship Anonymous, 1938. Bahr, 1952. Formosa Gov't.-Gen. Fish. Expt. Sta. ,1933. Hiratsuka and Imaizumi, 1934a, 1934b. Hiratsuka and Morita, 1935, 1936. J- Ikebe, 1940b, 1940c, 1941. Length-weight relationship — Continued Inanami, 1940. Kagoshima Pref. Fish. Expt. Sta., 1936a, 1937a. 1938a, 1939a, 1940a, 1941a. Kanamura and Imaizumi, 1936a. Kanamura and Yazakl, 1940b. Kawasaki, 1952. Miyama et al., 1939. Nakamura, 1936. Schaefer, 1948a. Schweigger, 1949. Serventy, 1941a. South Seas Gov't. . . . 1941c, 1943a, Uno, 1936b. Westman and Neville, 1942. Yabe and Mori, 1948. Little tuna (tunny). See Euthynnus atletteratus. Livebait fishing Anonymous, 1937b. Chapman, 1946. Chiba Pref. Fish. Expt. Sta., Katsuura Branch, 1941c. De La Tourrasse, 1951. Domantay, 1940a, 1940b. Flett, 1944. Higashi, 1941b. Ikebe and Matsumoto, 1938. Ikeda, 1932. Ikehara, 1953. Imamura, 1953. June, 1951b. June and Reintjes, 1953. Kagoshima Pref. Fish. Expt Sta., 1935b, 1936b, 1937c, 1938b, 1939b, 1940b, 1941a. Kanai and Kasu, 1938. Matsubara, 1943. Matsumoto, T., 1937. Miura, 1941. Murphy and Niska, 1953. Okajima, 1939. Powell. D. E. and Hildebrand, 1950. Sette, 1954. Shimoda, 1937. South Seas Gov't. . . . 1937. Yabe and Mori, 1950. Longline fishing Anonj-mous, 1937a, 1938, 1941a, 1941c. Chiba Pref. Fish. Expt. Sta., 1936b. Chiba Pref. Fish. Expt. Sta., Katsuura Branch, 1937b. 1938b, 1941a, 1941b, 1941f. Ikebe, 1941a. Imaizumi, 1937. Iwate Pref. Fish. Expt. Sta., 1953a, 1953b. June. 1950a, 1950b. Kagoshima Pref. Fish. Expt. Sta., 1930b, 1930c, 1931a, 1931b, 1932a, 1932b, 1932c, 1933b, 1935b. Kanagawa Pref. Fish. Expt. Sta., 1951b, 1952a, 1952b. Kanamura and Imaizumi, 1936a, 1936b. Kanamura and Yazaki, 1940a, 1940b. 236 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE Longline fishing — Continued Kato, 1940. McKeman, 1953. Matsubara, 1943. Mie Pref. Fish. Expt. Sta., 1950. MiyazEiki Pref. High-Seas Fish. Guidance Center, 1953. Murphy and Shomura, 1952. 1953a, 1953b. Nakamura, 1951. Nakayama, 1948. Nankai Reg. Fish. Res. Lab., 1951a, 1951b. Niska, 1953. Nomura at al., 1952-53. Okajima, 1939. omori and Fujimoto, 1940. omori and Fukuda, 1938, 1940. Powell, D. E., 1950. Powell et al., 1952. Rasalan, 1950. Sakai and Uno, 1940. Schaefers, 1952. Sette, 1954. Shapiro, 1950. Shimada, 1951c. Shimoda, 1937. South Seas Govt'. . . . 1937, 1942, 1943a. Tapiador, 1951. Uda, 1935a. Van Campen and Shimada, 1951. Watanabe, Haruo, 1940. Yoshihara, 1951-52. Mackerel, frigate. See Auicis spp. Management Okumura, 1943. Schaefer, 1948c, 1951. Measurement data. See also Morphometries. Kagoshima, 1936a, 1937a, 1938a, 1939a, 1940a, 1941a. Marr, 1948. Russell, F. S., 1934a. Schaefer, 1952. Schaefer and Walford, 1950. Measuring methods LeGall, 1951. Marr and Schaefer, 1949. Priol, 1944. Russell, F. S., 1934a. Mebachi. See Parathunnus mebachi. Mediterranean Sea and Strait of Gibraltar Anonymous, 1932. Arcidiacono, 1935. Aric6 and Genovese, 1953. Auffret, 1931. Bonamico, 1933. Cerequetelli, 1936. DeBuen, 1931. Dieuzeide, 1930. Farina, 1931a, 1931b. Frade, 1937b, 1953. Genovese, 1952. 1953. Mediterranean Sea and Strsiit of Gibraltar — Continued Heldt, 1932a, 1934, 1937, 1938, 1943. Maldura, 1946. Reiss and Vellinger, 1929. Russell, F. S., 1934b. Sanzo, 1932, 1933. Scordia, 1930, 1939a, 1940, 1943. Sigma, 1941. Meristic counts Conseil Int'l pour 1' EJxploration de la Mer, 1933. Godsil and Byers, 1944, Heldt, 1931a, 1932b. June, 1952a, 1952b. Letaconnoux, 1950. Marr and Schaefer, 1949. Schaefer and Marr, 1948a. Schaefer and Walford, 1950. Wade, 1949. Migration Bini, 1952. DeBuen, 1931. Hatai et al., 1941. Heldt 1930, 1931a, 1932a, 1932b, 1934, 1943. Kagoshima Pref. Fish. Expt. Sta., 1936c. Kajnimura and Honma, 1953. Kawasaki, 1952. Kimura, 1941, 1942b. LeDanois, 1938, 1951. Marukawa, 1939c. Nakamura, 1949. Powell, D. E., et al., 1952. Reiss and Vellinger, 1929. Ros6n, 1943. Russell, F. S., 1936. Sasaki, 1939a. Schaefers, 1953. Scordia, 1940. Sella, 1930, 1931, 1952. Serventy, 1941a. Shapiro, 1948a, 1948b. Sigma, 1941. Tauchi, 1940b. Tominaga, 1943. Uda. 1936a. Uda and Tokunaga, 1937. Wade, 1951. Walford, 1937. Whitehead, 1931. Yabuta and Ueyanagi, 1953. Miscellaneous species (Auxis to Neothunnus) Manter, 1940. Mather, 1954. Rivas, 1951. Tubb, 1948. Warfel, 1950. Miscellaneous species (Orcynus to Wanderer) Boeseman, 1947. Chu, 1931. DeBeaufort and Chapman, 1951. Fowler, 1949. ,-, BXBLJOGRAPHY ON THE TUNAS 237 Miscellaneous Species — Continued Ginsburg, 1953. Rivas, 1951. Schaefer, 1951. Schaefers, 1952, 1953. SeUa, 1931. Morphometries Aikawa and Kato, 1938. Aric6 and Genovese, 1953. Bell6n and BardAn de Bell6n, 1949. Bini, 1931. Bonliam, 1946. Conseil Int'l pour 1' Exploration de la Mer, 1933. DeBuen, 1932. Dung and Royce, 1953. Frade, 1931a, 1931b. Godsil, 1948, 1949. Godsil and Byers, 1944. Greenhood, 1952. Heldt, 1937, 1938. Higashi, 1942. Hiratsuka eind Morita, 1935, 1936. Ikebe and Matsumoto, 1937. Inanami, 1942d. Jap. Bur. Fish., 1939, 1940. June, 1952a, 1952b. LeGall, 1949, 1951. Legendre, 1934. Letaconnoux, 1950. Marr and Schaefer, 1949. Mather, 1954. Nakamura, 1939b, 1939c. Navaz, 1950. Oita Pref. Fish. Expt. Sta., 1930. Priol, 1944. Royce, 1953. Russell, F. S., 1934a. Schaefer, 1948a, 1951, 1952. Schaefer and Walford, 1950. Serventy, 1948. Uda, 1941. Watanabe, Hajime, 1939. Yabe et al., 1953. Neothunnus (Neothynnus) Abe, 1939. Aikawa, 1933. Aikawa and Kato, 1938. Ancieta C, 1952. Arai and Matsumoto, 1953. Ban, 1941. Barnard, 1948. Bamhart, 1936. Bates, 1950. Beebe, 1936. Beebe and Tee-Van, 1936. Bini, 1931, 1952. Boeseman, 1947. Bonham, 1946. Brock, 1949. Neothunnus (Neothynnus) — Continued Chapman, 1946. Chiba Pref. Fish .Expt. Sta., 1936b. Chiba Pref. F^sh. Expt. Sta., Katsuura Branch, 1941f. Chu, 1931. Copley, 1947. DeBeaufort and Chapman, 1951. DeBuen, 1930, 1935. Delsman and Hardenburg, 1934. Domantay, 1940. Dung and Royce, 1953. Eckles, 1949a. Fish, 1948. Fisheries Society of Japan, 1931. Fitch, 1950. Food and Agr. Organ. U. N., 1949b. Formosa Gov't. -Gen. Fish. Expt. Sta., 1933a, 1933b. Fowler, 1931, 1936, 1949. Frade, 1931b, 1931c. Ginsburg, 1953. Godsil, 1936, 1938a, 1938b, 1945, 1948, 1949a, 1949b. Godsil and Byers, 1944. Godsil and Greenhood, 1948, 1951, 1952. Greenhood, 1952. Hatai et al., 1941. Herald, 1949. Herre, 1932, 1935, 1936, 1940. Herre and Umali, 1948. Higashi, 1940, 1941, 1942. Higashi £ind Hirai, 1948. Hildebrand, 1946. Hiratsuka emd Imaizumi, 1934. Hiratsuka and Ito, 1934. Hiratsuka and Morita, 1935, 1936. Ikebe, 1939a, 1939b, 1940a, 1940b, 1940c, 1940d, 1941b, 1941c, 1942. Inanami, 1940a, 1940b, 1940c, 1942a, 1942b. Iwate Pref. Fish. Expt. Sta., 1953a, 1953b. Jap. Bur. Fish., 1933, 1934, 1935. June, 1952b, 1953. Kagoshima Pref. Fish. Expt. Sta., 1930b, 1930c, 1931b, 1933b. Kanamura and Imaizumi, 1936a. Kanamura and Yazaki, 1940a, 1940b. Kato, 1940. Kawamura, 1939. Kimura, 1932, 1935, 1942a, 1942b. Kimura and Ishii, 1932, 1933b. Kumata et al., 1941. Marr, 1948. Martin, 1938. Marukawa, 1939b, 1939c. Mather, 1954. Mead, 1951. Mie Pref. Fish. Expt. Sta., 1930c, 19306. Migita and Arakawa, 1948. Miura, 1941. Miyama and Osakabe, 1940. Miyama et al., 1939. 288 FISHERY BTJLIjETINOm THE FISH AND WILDLIFE SERVICE Neothunntis (Neothy^mnsJ— Continued ■.-■ :m Miyazaki Pref., High-Seas Fish. Guidance Center, 1953. Molteno, 1948. Moore, 1951a, 1951b. Morice, 1953a, 1953b. Morrow, 1954. :», ;, Murphy and Niska, 1953. ' : "":i'" Murphy and Shomura, 1953a, 1953T3. Nakamura, 1936, 1939a, 1939b, 1939c,. 1941, 1943, -■ 1949, 1951. :- Nankai Reg. Fish. Res. Lab., 19f51a. .': ^i.'.vC; Nichols and LaMonte, 1941. ; "'.' ::-'^ Nigrelli and Stunkard, 1947. ►- Nomura et al., 1952-53. Oita Pref. Fish. Expt. Sta., 1930. Okada and Matsubara, 1938. Okada et al., 1935. Okinawa Pref. Fish. Expt. Sta., 1936b. okuma et al., 1935. Phillipps, 1932. Powell, A. W. B., 1937. Rawlings, 1953. Reintjes, 1952 Reintjes and King, 1953. Rivas, 1951, 1953. Roedel, 1948a. Ronquillo, 1953. Royce, 1953. Schaefer, 1948a, 1948b, 1948c, 1951, 1952. Schaefer and Marr, 1948b. Schaefer and Walford, 1950. Schweigger, 1943, 1949. Seale, 1940. Serventy, 1941a, 1941b. Sette, 1954. Shapiro, 1948, 1948b. Shimada, 1951, 1954. Smith and Schaefer, 1949. Smith, 1947. Soldatov and Lindberg, 1930. South Seas Gov't'. . . . 1937a, 1938, 1941a, 1941d, 1942, 1943a, 1943b. Suda, 1953. Suyehiro, 1941, 1942. Tanaka, 1931. Tapiador, 1951. Taranetz, 1937. Tauchi, 1940b. Tester, 1952. Tester et al., 1952. Tinker, 1944. Toyama, Y., et al., 1941. Uda, 1935a, 1952. Uehara, 1941. Van Campen, 1952. Wade, 1950a, 1950b, 1951. Walford, 1931, 1937. Warfel, 1950. Watanabe, Haruo, 1940. Neothunnus {Neothynnus)-^.Contixiued. Tj!i!i':.:-£.\\;'. Welsh, 1949a, 1949c. • ty ; • Whitley, 1947. : i. Yabe et al., 1953. Yabe and Mori, 1950. Yabuta, 1953. Yabuta and Ueyanagi, 1953a, 1953b. Neothunnus albacora Barnard, 1948. Blni, 1931. DeBuen, 1930, 1935. Frade, 1931b, 1931c. Marukawa, 1939c. Navarro and Lozano, 1950. Nichols and LaMonte, 1941. Schaefer and Walford, 1950. Neothunnus albacares. See N. macropterus. N. albacora albacora. See N. macropterus. N. albacora macropterus. See N. macropterus, N. allisoni Nichols and LaMonte, 1941. Walford, 1937. N. allisoni allisoni. See N. allisoni. N. allisoni itosibi. See N. itosibi. N. argentivitattus Beebe, 1936. Beebe and Tee-Van, 1936. Fowler, 1944. Rawlings, 1953. N. catalinae Nichols and LaMonte, 1941. N. itosibi Domantay, 1940b. Martin, 1938. Molteno, 1948. Nakamura, 1939c. Okada and Matsubara, 1938. Phillipps, 1932. Powell, A. W. B., 1937. N. m,acropterus Abe, 1939. Aikawa, 1933. Aikawa and Kato, 1938. Ancieta C, 1952. Anonymous, 1938. Aral and Matsumoto, 1953. Asakawa, Noguchl, and Mimoto, 1953. Ban, 1941. Barnhart, 1936. Bates, 1950. Bini, 1952. Boeseman, 1947. Bonham, 1946. Brock, 1949. Chapman, 1946. Chiba Pref. Fish. Expt. Sta., 1936b. Chiba Pref. Fish. Expt. Sta., Katsuura Branch, 1941. Chu, 1931. Copley, 1947. ■JBIBLilOGRAPHYiON! THE TUNAS 239 N. macropterus — Continued p^eaufort and Chapman, 1951. DeBuen, 1935. Delsman and Hardenburg, 1934. Domantay, 1940. Dung and Royce, 1953. Eckles, 1949a. Fish, 1948. Fisheries Society of Japan, 1931. Fitch, 1950. Food and Agr. Organ. U. N., 1949b. Formosa Gov't.-Gen. Fish. Expt. Sta., 1933a. Fowler, 1931, 1936, 1949. Ginsburg, 1953. Godsil, 1936, 1938a, 1938b, 1945, 1948, 1949a, 1949b. Godsil and Byers, 1944. Godsil and Greenhood, 1948, 1951, 1952. Greenhood, 1952. Hatai et al., 1941. Herald, 1949. Herre, 1932, 1935, 1936, 1940. Herre and Umali, 1948. Higashi, 1940a, 1941a, 1941b, 1942. Higashi and Hirai, 1948. Hildebrand, 1946. Hiratsuka and Imaizumi, 1934. Hiratsuka and Ito, 1934. Hiratsuka and Morita, 1935, 1936. Ikebe, 1939a, 1939b, 1940a, 1940b, 1940d, 1941b, 1941c, 1942. Ikehara, 1953. Imaizumi, 1937. Inanami, 1940a, 1940b, 1940c, 1942a, 1942b. Iwate Pref. Fish. Expt. Sta., 1953a, 1953b. Jap. Bur. Fish., 1933, 1934, 1935. June, 1952b, 1953. Kagoshima Pref. Fish. Expt. Sta., 1930b, 1930c, 1931b, 1933b. Kanagawa Pref. Fish. Expt. Sta. 1951a. Kanamura and Imaizumi, 1936a. Kanamura and Yazaki, 1940a, 1940b. Kato, 1940. Kawamura, 1939. Kimura, 1932, 1935, 1942a, 1942b. Kimura and Ishii, 1932, 1933b. Kumata et al., 1941. Marr, 1948. Martin, 1938. Marukawa, 1939b. Mather, 1954. Mead, 1951. Mie Pref. Fish. Expt. Sta., 1930c, 1930d, 1930e. Migita and Arakawa, 1948. Miura, 1941. Miyama and Osakabe, 1940. Miyama et al., 1939. Miyazaki Pref. High-Seas Fish. Guidance Center, 1953. Moore, 1951a, 1951b. Morrow, 1954. N. macropterus — Continued Murphy and Niska, 1953. Murphy and Shorn ura, 1952, 1953a, 1953b. Nakamura, 1936, 1939a, 1939b, 1939c, 1941, 1943, . 1949, 1951. .f Nigrelli and Stunkard, 1947. ••■ . Nomura et al., 1952-53. Oita Pref. Fish. Expt. Sta., 1930. Okada and Matsubara, 1938. Okada et al., 1935. Okinawa Pref. Fish. Expt. Sta., 1936b. okuma et al., 1935. Reintjes, 1952. Reintjes and King, 1953. Roedel, 1948a. '^''''' ', Ronquillo, 1953. Royce, 1953. Schaefer, 1948a, 1948b, 1948c, 1951, 1952. Schaefer and Marr, 1948b. Schaefer and Walford, 1950. Schweigger, 1943, 1949. Seale, 1940. Serventy, 1941a, 1941b. Sette, 1954. Shapiro, 1948a, 1948b. Shimada, 1951b, 1954. Smith and Schaefer, 1949. Smith, 1947. Soldatov and Lindberg, 1930. South Seas Gov't. . . . 1937a, 1938, 1941a, 1941d, 1942, 1943a, 1943b. Suda, 1953. Suyehiro, 1941, 1942. Takayama and Ando, 1934. Tanaka, 1931. Tapiador, 1951. Taranetz, 1937. Tauchi, 1940b. Tester, 1952. Tester et al., 1952. Tinker, 1944. Toyama, Y., et al., 1941. Uda, 1952. Uehara, 1941. Van Campen, 1952. Wade, 1950a, 1950b, 1951. Walford, 1931, 1937. Warfel, 1950. Watanabe, Haruo, 1940. Welsh, 1949a, 1949c. Whitley, 1947. Yabe et al., 1953. Yabe and Mori, 1950. Yabuta, 1953. Yabuta and Ueyanagi, 1953a, 1953b. N. rarus Delsman and Hardenburg, 1934. Herre, 1940. Nakamura, 1943, 1949. Nichols and LaMonte, 1941. 240 FISHERT BULLETIN OF THE BISH AND WILDLIFE SERVICE N. rarua — Continued Serventy, 1942b. N. rarus zacalles. See Kishinoella zacallea. North Sea and English Channel Bahr, 1952. Delsman, 1933. Flck, 1937. Kreutzer, 1951a. LUUng, 1950, 1951, 1952b. Ros6n, 1943. Russell, F. S., 1933a, 1934a. Oceanographic conditions correlated with fishing or distribution Aikawa, 1933. Anonymous, 1937a, 1941c, 1942. Ban, 1941. Bini, 1952. Chiba Pref. Fish. Expt. Sta., 1936a. Chiba Pref. Fish. Expt. Sta., Katsuura Branch, 1937a, 1937b, 1938a, 1938b, 1941a, 1941b, 1941c, 1941d, 1941f. Formosa Gov't.-Gen. Fish. Expt. Sta., 1930, 1931, 1932, 1933a, 1933b, 1934. Fujii, 1932. Fukuda and lizuka, 1940. Genovese, 1952, 1953. Hart and HoUister, 1947. Hiratsuka and Imaizumi, 1934. Hiratsuka and Ito, 1934. lehisa, 1939. Ikebe, 1940b, 1941a, 1942. Ikebe and Matsumoto, 1937. Imamura, 1949. Inanami, 1938, 1940b, 1940c, 1941, 1942a, 1942b. Inoue, 1953. Jap. Bur. Fish. 1933, 1934, 1935, 1939, 1940. Kagoshima Pref. Fish. Expt. Sta., 1930a, 1930b, 1930c, 1931a, 1931b, 1932a, 1932c, 1933a, 1933b, 1934, 1935a, 1936a, 1937a. Kanagawa Pref. Fish. Expt. Sta., 1951a, 1951b, 1952a, 1952b. Kanamura and Imaizumi, 1936a. Kawamura, 1939. Kawana, 1934, 1937. Kawasaki, 1952. Kida, 1936. Kimura, 1941, 1942a, 1949. Kimura £ind Ishii, 1933b. Kumamoto Pref. Fish. Expt. Sta., 1946. LeDanois, 1933, 1938. Matsubara, 1943. Matsumoto, T., 1937. Mie Pref. Fish. Expt. Sta., 1930a, 1930b, 1930c, 1930d, 19306. Miyazaki Pref. High-Seas Fish. Guidance Center, 1953. Murphy and Niska, 1953. Murphy and Shomura, 1953a, 1953b. Nakamura, 1949. oita Pref. Fish. Expt. Sta., 1930. Oceanographic conditions — Continued Okinawa Pref. Fish. Expt Sta., 1940a, 1940b, 1943. Okuma, 1935. Omori and Fujimoto, 1940. Omori and Fukuda, 1940. Partlo, 1950, 1951. Powell, D. E. 1950. Powell and Hildebrand, 1950. Powell et al., 1952. Reiss and Vellinger, 1929. Sait6, 1937. Sasaki, 1932, 1939a, 1939b. Scagel, 1949. Schaefers, 1952, 1953. Shapiro, 1948b. Shizuoka Pref. Fish. Expt. Sta., 1936, 1937a. Society for the Promotion . . . 1936. South Seas Government . . . 1937c, 1938, 1941d 1942, 1943a, 1943b. Taihoku Prov. Fish. Expt. Sta., 1932. Takayama and And5, 1934. Takayama et al., 1934. Tapiador, 1951. Uda, 1931a, 1933, 1935a, 1935b, 1935c, 1936a, 1936b, 1938, 1939, 1940a, 1940b, 1941, 1948, 1952. Uda and Tokunaga, 1937. Uehara, 1941. Yabe et al., 1953. Yabuta, 1953. Yabuta and Ueyanagi, 1953a, 1953b. Orcynus Priol, 1944. Sanzo, 1932, 1933. Orcynus alalonga. See Germo. Orcynus germo. See Germo. Orcynus pacificus. See Germo. Orcynus thynnus. See Thunnus thynnus. Pacific Ocean, NE Bamhart, 1936. Bates, 1950. Brock, 1938, 1939, 1943, 1949, 1954. Chapman, 1946. Chiba Pref. Fish. Expt. Sta., Katsuura Branch, 1941e, 1941f. Clemens and Wilby, 1946. Cowan, 1938. Eckles, 1949a, 1949b. Fish, 1948. Fitch, 1950, 1953. Godsil, 1936, 1937, 1938a, 1938b, 1938c. Godsil and Greenhood, 1948, 1951, 1952. Godsil and Holmberg, 1950. Hart and HoUister, 1947. Hart et al., 1948. Ikehara, 1953. Inanami, 1941. June, 1950a, 1953. McHugh, 1952. McKeman, 1953. Matsui, Y., 1938. ',^ BIBLIOGRAPHY ON THE TUNAS 241 Pacific Ocean, NE — Continued Moore, 1951a, 1951b. Murphy and Niska, 1953. Murphy and Shomura, 1953a, 1953b. Nakamura et al., 1953. Niska, 1953. Partlo, 1950, 1951. PoweU, D. E., 1950. Powell and Hildebrand, 1950. PoweU et al., 1952. Reintjes and King, 1953. Roedel, 1948a, 1948b. Samson, 1940. Schaefer, 1948a, 1948b, 1952. Schaefer and Marr, 1948a, 1948b. Schaefer and Walford, 1950. Schaefers, 1952, 1953. Schultz and DeLacy, 1936. Sette, 1954. Smith and Schaefer, 1949. South Seas Gov't. . . . 1943£L Tester, 1952. Tinker, 1944. Van Campen and Shimada, 1951. Walford, 1931, 1937. Welsh, 1949a, 1949b, 1949c. Whitehead, 1930, 1931. Pacific Ocean, NW Abe, 1939. Aikawa, 1932, 1933, 1937. Anonymous, 1939, 1941b, 1941c. Boeseman, 1947. Chapman, 1946. Chevey, 1932a, 1934. Chiba Pref. Fish. Expt. Sta., 1936a, 1936b. Chiba Pref. Fish. Expt. Sta., Katsuura Branch, 1937a, 1937b, 1938a, 1938b, 1941a, 1941b, 1941d, 1941e. Cleaver and Shimada, 1950. DeJong, 1940. Delsman, 1931. Domantay, 1940a, 1940b. Ego and Otsu, 1952. Espenshade, 1948. Fish, 1948. Fisheries Society of Japan, 1931. Formosa Gov't.-Gen. Fish. Expt. Sta., 1930, 1931, 1932, 1933a, 1933b, 1934. Fujii, 1932. Fukuda Eind lizuka, 1940a, 1940b. Hasegawa, Kiichl, 1937. Hasegawa, Kimpei, 1938. Hatai et al., 1941. Herre, 1933, 1935. Herre and Umali, 1948. Hiatt and Brock, 1948. Hiratsuka and It6, 1934. Hiratsuka and Morita, 1935, 1936. lehisEi, 1939. Ikebe, 1938, 1939a, 1939b, 1940a, 1940b, 1940c, Pacific Ocean, NE — Continued 1940d, 1941c. Ikebe and Matsumoto, 1937a. Ikeda, 1932. Ikeda and Ando, 1933. Imamura, 1949. Inanami, 1940a, 1940b, 1942a, 1942b, 1942c, 1942d. Jap. Bur. Fish. 1933, 1934, 1935, 1940, 1942. June, 1951b, 1952a, 1952b. Kagoshima Pref. Fish. Expt. Sta., 1930a, 1930b. 1930c, 1931a, 1932a, 1932c, 1 1933a, 1933b, 1934. 1935a, 1935b, 1936b, 1937a, 1937b, 937c. 1938a, 1938b, 1938c, 1939a, 1939b, 1939c, 1940a, 1940b. 1940c, 1941a, 1941b. Kanagawa Pref. Fish. Expt. Sta., 1951a, 1951b. 1952a, 1952b. Kanai, Moto and Kasu, 1938. Kanamura and Imaizumi, 1936a. 1936b. Kanamura and Yazaki, 1940b. Kato, 1940. Kawamura, 1939. Kawana, 1934, 1935, 1938. Kida, 1936. Kikawa, 1953. Kimura, 1933, 1935, 1941, 1942a, 1942b, 1949. Kimura and Ishii, 1931, 1932, 1933b. Koyasu, 1931. Kumamoto Pref. Fish. Expt. Sta., 1946. McKeman, 1953. Manter, 1940. Matsubara, 1943. Matsui, K., 1942b. Mie Pref. Fish. Expt. Sta., 1930a, 1930b, 1930c. 1930d, 1930e, 1950a, 1950b, 1950c. Mine and lehisa, 1940. Miura, 1941. Murayama and Okura, 1950, 1952. Nakamura, 1938, 1939b, 1939c, 1941, 1943, 1949, 1951. Nakamura, et al., 1953. Nankai Reg. Fish. Res. Lab., 1951a, 1951b. Noguchi, 1938. Nomura et aJ., 1952-53. 6ita Pref. Fish. Expt. Sta., 1930. Okada and Matsubara, 1938. Okajima, 1939. Okamoto, 1940. Okinawa Pref. Fish. Expt. Sta., 1931, 1936a, 1940a, 1940b. okuma et al., 1935. Omori and Fujimoto, 1940. 6mori and Fukuda, 1938, 1940. Onodera, 1941. Rasalan, 1950. Ronquillo, 1953. Sakai and Uno, 1940. Sasaki, 1932, 1939a, 1939b. Sasaki, and Takehisa, 1932. Scagel, 1949. Schmidt, 1930. 242 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE Pacific Ocean, NW — Continued Shapiro, 1948a, 1948b. Shimada, 1951b, 1951c. Shizuoka Pref. Fish. Expt. Sta., 1936, 1937a, 1937b. Smith and Schaefer, 1949. Smith, 1947. Society for the Promotion . . . 1936, 1937a. Soldatov and Lindberg, 1930. South Seas Gov't. . . . 1937a, 1937b, 1937c, 1937d, 1938, 1941a, 1941b, 1941c, 1941d, 1942, 1943a, 1943b. Suda, 1953. Sugiura, 1932. Tachikawa, 1932. Taihoku Prov. Fish. Expt. Sta., 1932. Takayama and Ando, 1934. Takayama at al., 1934. Tanaka, 1931, 1936, 1939. Tapiador, 1951. Taranetz, 1937. Tauchi, 1940a, 1940b, 1940c, 1943. Tominaga, 1943. Uda, 1931a, 1931b, 1932a, 1933, 1935a, 1935b, 1935c, 1936a, 1938, 1939, 1940b, 1940c, 1941, 1948, 1952. Uda and Tokunaga, 1937. Uda and Tsukushi, 1934. Uehara, 1941. Uno, 1936a. Van Campen and Shimada, 1951. Wade, 1950a. Warfel, 1950. Watanabe, Hajime, 1939. Watanabe, Haruo, 1940. Watanabe, Nobuo, 1941. Yabe, 1953. Yabe et al., 1953. Yabe and Mori, 1950. Yabuta, 1953. Yabuta and Ueyanagi, 1953a. Yamamoto, Shokichi, 1940. Pacific Ocean, SE Ancieta C, 1952. Bini, 1952. Chapman, 1946. Fish, 1948. Fowler, 1938. Schweigger, 1943, 1949. Scale, 1940. Shimada, 1951d, 1954. Van Campen, 1953. Pacific Ocean, SW Anonymous, 1953a. Ban, 1941. Chapman, 1946. Fish, 1948. Flett, 1944. Formosa Gov't. Gen. Fish. Expt. Sta., 1933. Fowler, 1938. Godsil and Holmberg, 1950. Pacific Ocean SW — Continued Ikebe, 1941b. McKeman, 1953. Nomura et al., 1952-53. PhilUpps, 1932. Robins, 1952. Saito, 1937. Serventy, 1941a, 1941b, 1942a, 1942b, 1947, 1948. Whitley, 1937, 1947. Parasites Arai and Matsumoto, 1953. Crane, 1936. LeGall, 1949. Legendre, 1940. Manter, 1940. Nigrelli and Stunkard, 1947. Priol, 1944. Van Cleave, 1940. Parathunnus (Parathynnus) Aikawa, 1933. Asakawa, Noguchi, and Mimoto, 1953. Beebe, 1936. Beebe and Tee-Van, 1936. Bell6n and Barddn de Bell6n, 1949. Bini, 1931. Brock, 1949. Chiba Pref. Fish. Expt. Sta., 1936b. Chiba Pref. Fish. Expt. Sta., Katsuura Branch, 1941e, 1941f. DeBeaufort and Chapman, 1951. DeBuen, 1930. Domantay, 1940b. Dung and Royce, 1953. Fish, 1948. Fisheries Society of Japan, 1931. Fowler, 1931, 1938, 1949. Frade, 1931b. Fukuda and lizuka, 1940. Godsil, 1945. Godsil and Byers, 1944. Hatai et al., 1941. Herre, 1940. Higashi, 1940a, 1941b. Ikebe, 1939a, 1940a, 1942. Inanami, 1940b, 1940c. Iwate Pref. Fish. Expt. Sta., 1953a, 1953b. Jap. Bur. Fish., 1933, 1934, 1939. Kagoshima Pref. Fish. Expt. Sta., 1930b, 1930c, 1931b, 1933b. Kamimura and Honma, 1953. Kanagawa Pref. Fish. Expt. Sta., 1951a, 1952a. 1952b. Kanamura and Imaizumi, 1936a. Kanamura and Yazaki, 1940a. Kikawa, 1953. Kimura, 1942a, 1942b. Kimura, Iwashita, and Hattori, 1952. Kumata et al., 1941. Mie Pref. Fish. Expt. Sta., 1930c, 1930e. Miyama and Osakabe, 1938, 1340. BIBLIOGRAPHY ON THE TUNAS 243 Parathunntis (Parathynnus) — Continued Miyazaki Pref. High-Seas Fish., Guidance Center, 1953. Molteno, 1948. Morice, 1953b. Mowbray, 1935. Murphy and Shomura, 1953a, 1953b. Nakamura, 1939a, 1939b, 1941, 1943, 1949, 1951, 1953. Nankai Reg. Fish. Res. Lab., 1951a. Navarro and Lozano, 1950. Nomura et al., 1952-53. Oita Pref. Fish. Expt. Sta., 1930. Okada and Matsubara, 1938. Okada et al., 1935. Okinawa Pref. Fish. Expt. Sta., 1940b. omori and Fujimoto, 1940. omori and Fukuda, 1938, 1940. Rivas, 1953. Roedel, 1948a. Schaefer, 1951. Schuck and Mather, 1951. Shapiro, 1948a. Shimada, 1951b, 1954. Smith and Schaefer, 1949. Soldatov and Lindberg, 1930. South Seas Government . . . 1941a, 1942. Suda, 1953. Suyehiro, 1941, 1942. Takayama and Ando, 1934. Toyama, Y., et al., 1941. Uda, 1935a. Uehara, 1941. Van Campen, 1952. Watanabe, Haruo, 1940. Yabuta, 1953. Yabuta and Ueyanagi, 1953a. Parathunnus atlanticus Beebe, 1936. Beebe and Tee-Van, 1936. Bell6n and Bard^n de Bell6n, 1949. Bini, 1931. DeBuen, 1930. Frade, 1931b. Legendre, 1937. Marukawa, 1939b, 1939c. Mather, 1954. Molteno, 1948. Morice, 1953b. Mowbray, 1935. Navarro and Lozano, 1950. Nigrelli and Stunkard, 1947. Rawlings, 1953. Schuck and Mather, 1951. Paiathunnus mebachi Asakawa, Noguchi, and Mimoto, 1953. Fish, 1948. Godsil, 1945. Godsil and Byers, 1944. Ikebe, 1939a. Kamimura and Honma, 1953. Parathunnus (Parathynnus J — Continued Kikawa, 1953. Kumata et al., 1941. Mie Pref. Fish. Expt. Sta., 1930a, 1930d. Nakamura, 1939a, 1939b, 1943, 1949. Nakamura et al., 1953. Roedel, 1948a. South Seas Government . . . 1941a. Takayama and Ando, 1934. Parathunnus obesus. See P. atlanticus. Parathunnus sibi Aikawa, 1933. Brock, 1949. Chiba Pref. Fish. Expt. Sta., 1936b. Chiba Pref. Expt. Sta., Katsuura Branch, 1941e, 1941f. DeBeaufort and Chapman, 1951. Domantay, 1940b. Dung and Royce, 1953. Fisheries Society of Japan, 1931. Fowler, 1931, 1938, 1949. Fukuda and lizuka, 1940a. Hatai et al., 1941. Herre, 1940. Higashi, 1940a, 1941b. Ikebe, 1940a, 1942. Inanami, 1940b, 1940c. Iwate Pref. Fish. Expt. Sta., 1953a, 1953b. Jap. Bur. Fish., 1934, 1935, 1939. Kagoshima Pref. Fish. Expt. Sta., 1930b, 1930c, 1931b, 1933b. Kanagawa Pref. Fish. Expt. Sta., 1951a, 1952a, 1952b. Kanamura and Imaizumi, 1936a. Kanamura and Yazaki, 1940a. Kimura, 1942a, 1942b. Kimura, Iwashita, and Hattori, 1952. Kumata et al., 1941. Marukawa, 1939b. Mie Pref. Fish. Expt. Sta., 1930c, 1930e. Miyama and Osakabe, 1938, 1940. Miyazaki Pref. High-Seas Fish. Guidance Center, 1953. Murphy and Shomura, 1953a, 1953b. Nakamura, 1941, 1951. Nankai Reg. Fish. Res. Lab. 1951a. Nomura et al., 1952-53. oita Pref. Fish. Expt. Sta., 1930. Okada and Matsubara, 1938. Okada et al., 1935. Okinawa Pref. Fish. Expt. Sta., 1940b. omori and Fujimoto, 1940. omori and Fukuda, 1938, 1940. Schaefer, 1951. Shapiro, 1948a. Shimada, 1951b, 1954. Smith and Schaefer, 1949. South Seas Gov't 1942. Suda, 1953. Suyehiro, 1941, 1942. Toyama, Y., et al., 1941. 244 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE Parathunnus sibi — Continued Uda, 1935a. Uehara, 1941. Van Campen, 1952. Watanabe, Haruo, 1940. Yabuta, 1953. Yabuta and Ueyanagi, 1953a. Yoshihara, 1951-52. Parathynnus sibi. See Parathunnus sibi. Pelamys (Pelamis) Maldura, 1946. Pelamys affine. See Euthynnus alletteratus. Pelamys macropterus. See Neothunnus macropterus. Pelamys pelamys. See Katsuwonus. Population dynamics Aikawa, 1937. Bini, 1952. Brock, 1943. Tauchi, 1940a, 1940b, 1940c, 1943. Tominaga, 1943. Populations, definition of Godsil and Byers, 1944. Royce, 1953. Schaefer, 1951, 1952. Schaefer and Walford, 1950. Sette, 1954. Uda and Tokunaga, 1937. Uda and Tsukushi, 1934. Purse-seining Carlson, 1951. Heldt, 1932b. Imamura, 1953. Murayama and Okura, 1950, 1952. Murphy and Niska, 1953. Murray, 1952. Sette, 1954. Reactions to stimuli Tester et al., 1952. Red Sea Copley, 1947. Red tuna. See Thunnus thynnus. Reproduction Anonymous, 1941b. Bini, 1952. Brock, 1943. DeBuen, 1931, 1937. DeJong, 1940. Eckles, 1949b. Frade and Managas, 1933. Genovese, 1953. Hatai et al., 1941. Heldt, 1934. Ikebe, 1941b. June, 1953. Kamimura and Honma, 1953. Kawana, 1935. Kikawa, 1953. Kuronuma et al., 1949. LeDanois, 1951. LeGall, 1949. Reproduction — Continued Lozano, 1950. Marr, 1948. Marukawa, 1939c. Mead, 1951. Nakamura, 1938, 1939b, 1943, 1949. Okada et al., 1935. Priol, 1944. Sanzo, 1933. Schaefer, 1948c, 1951. Schaefer and Marr, 1948b. Sella, 1952. Serventy, 1941a, 1942a. Sette, 1954. Shapiro, 1948a. Society for the Promotion . . . 1936. Wade, 1950b. Walford, 1937. Watanabe, Hajime, 1939. Whitehead, 1931. Yabe and Mori, 1948. Rote Thun. See Thunnus thynnus. Salinity. See Oceanographic conditions and related subjects. Scomber Conrad, 1937. Scouting methods Heldt, 1932a. SewMthunnus Fowler, 1933, 1934. Nakamura, 1939c. Tinker, 1944. Sex. See Morphometries Sex ratios Brock, 1943, 1954. Crane, 1936. Iwate Pref. Fish. Expt. Sta., 1953a, 1953b. Kanagawa Pref. Fish. Expt. Sta., 1952a, 1952b. Marr, 1948. Miyazaki Pref. High-Seas Fish., Guidance Center, 1953. Murphy and Shomura, 1953a, 1953b. Schweigger, 1949. Size composition Aikawa, 1937. Aikawa and Kato, 1938. Bonham, 1946. Brock, 1943. Hart et al., 1948. Inanami, 1942c. Kagoshima Pref. Fish. Expt. Sta., 1937a. Kamimura and Honma, 1953. Kanagawa Pref. Fish. Expt. Sta., 1951a, 1951b, 1952b. Kawana, 1934. Kawasaki, 1952. Kida, 1936. Kikawa, 1953. Kimura, 1935, 1941, 1942a. Kimura and Ishii, 1933a. Mine and lehisa, 1940. BIBLJOGRAPHT ON THE TUNAS 245 Size composition — Continued Miyazaki Pref . High-Seas Fish. Guidance Center, 1953. Murphy and Shomura, 1953a, 1953b. Nakamura et al., 1953. Nankai Reg. Fish. Res. Lab., 1951b. Nomura et al., 1952-53. Okamoto, 1940. Okinawa Pref. Fish. Expt. Sta., 1931. okuma et al., 1935. Onodera, 1941. Partlo, 1951. Powell, D. E., 1950. Powell and Hildebrand, 1950. Powell et al., 1952. Sasaki, 1939a, 1939b. Scagel, 1949. Schaefer, 1948b, 1951. Schaefer and Marr, 1948b. Schaefers, 1953. Schweigger, 1949. Serventy, 1947. Sette, 1954. Tauchi, 1940a, 1940b, 1940c. Uda, 1932b. Uda and Tsukushi, 1934. Westman and Neville, 1942. Yabe and Mori, 1950. Yabuta and Ueyanagi, 1953a, 1953b. Yamanaka, 1950. Skipjack. See Katsuioonus. Skipjack, black. See Euthynnus spp. S6dagatsuwo. See Auxis spp. South China Sea Anonymous, 1938. Kanamura and Imaizumi, 1936b. Southern bluef in tuna. See Thunnus maccoyi Spawning. See Reproduction. Statistics Alaejos, 1931. Anderson, Stolting, et al., 1953. Anonymous, (1), (2), (3), 1932, 1945, 1947, 1949a, 1949b, 1952. California. Dept. Fish and Game California. Dept. Fish and Game, Marine Fish. Br. Chiba Pref. Fish. Expt. Sta., 1936b. Chiba Pref. Fish. Expt. Sta., Katsuura Branch, 1938b, 1941e, 1941f. Conseil Int'l'. pour 1' Exploration de la Mer, 1933. Ego and Otsu, 1952. Ehrenbaum, 1934. Espenshade, 1948. Farina, 1931a. Federation of Japan Tuna . . . 1951a, 1951b, 1952, 1953a, 1953b. Food and Agr. Organ. U. N., 1949a. Godsil, 1937, 1949. Kanai, Moto and Kasu, 1938. LUling, 1951, 1952b. Nakayama, 1948. Statistics — Continued Navaz, 1950. South Seas Gov't 1938. U. S. Fish and Wildlife Service. Stomach contents. See Food. Striped tuna. See Katsuwonus. Sumagatsuo. See Euthynnits yaito. Synonymy Barnard, 1948. Beebe and Tee-Van, 1936. Boeseman, 1947. Chevey, 1932b. Chu, 1931. DeBeaufort and Chapman, 1951. DeBuen, 1935. Fish, 1948. Food and Agr. Organ. U. N., 1949b. Fowler, 1931, 1934, 1936, 1949. Frade, 1931c. Fraser-Brunner, 1949, 1950. Ginsburg, 1953. Heldt, 1930, 1931a, 1931b. Herre, 1936. Hildebrand, 1946. Joubin, 1934. LeGall, 1934a, 1934b, 1934c, 1934d. Maldura, 1946. Molteno, 1948. Nakamura, 1939b, 1939c. Nichols and LaMonte, 1941. Powell, A. W. B., 1937. Rosa, 1950. Schaefer and Walford, 1950. Schultz, 1949. Schultz and DeLacy, 1936. Serventy, 1942b. Soldatov and Lindberg, 1930. Tanaka, 1931. Wade, 1949. Whitley, 1937. Tagging Alverson and Chenowith, 1951. Anonymous, 1939a. Conseil Int'l pour 1' Exploration de la Mer, 1933. Fukuda and lizuka, 1940b. Ganssle and Clemens, 1953. Godsil, 1936, 1938b, 1938c. Heldt, 1932b. Kagoshima Pref. Fish. Expt. Sta., 1936c, 1938c, 1939c, 1940c. Kawana, 1934. Matsumoto, T., 1937. Partlo, 1950, 1951. Powell, D. E., 1950. Powell et al., 1952. Russell, F. S., 1934a. Scagel, 1949. Schaefers, 1952, 1953. South Seas Gov't. . . . liJ41b. 246 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE Tagg-ing — Continued Uda, 1936a. Wilson, 1953. Temperature. See Body temperature, oceanographic conditions. Thon blanc. See Germo. Thon rouge. See Thunnus thynnus. Thunnidae Bellbn and Bardan de Bell6n, 1949. Nakamura, 1939b, 1941. Thunniformes Berg, 1947. Thunniinae Frade, 1932. Thunmis Aikawa, 1933. Aikawa and Kato, 1938. Alaejos, 1931. Aricb and Genovese, 1953. Bahr, 1952. Barnhart, 1936. Bigelow and Schroeder, 1953. Blackburn and Rayner, 1951. Boeseman, 1947. Bonamico, 1933. Brock, 1938, 1949. Cerquetelli, 1936. Chabanaud, 1930. Conrad, 1937. Conseil Int'l pour 1' Exploration de la Mer, 1933. Crane, 1936. DeBeaufort and Chapman, 1951. DeBuen, 1930, 1931, 1932, 1935, 1937. De La Tourrasse, 1951. Delsman, 1933. Dieuzeide, 1930, 1931. Dung and Royce, 1953. Ehrenbaum, 1934. Fick, 1937. Fish, 1948. Fisheries Society of Japan, 1931. Food and Agr. Organ. U. N., 1949b. Fowler, 1931, 1934, 1936, 1938, 1944. Frade, 1930a, 1930b, 1931a, 1931b, 1931d, 1935, 1937a, 1937b, 1953. Frade and Managas, 1933. Fraser-Brunner, 1950. Fujii, 1932. Galtsoff, 1952. Genovese, 1952, 1953. Ginsburg, 1953. Godsil, 1945, 1949b. Godsil and Byers, 1944. Godsil and Holmberg, 1950. Heldt, 1930, 1931a, 1931b, 1932b, 1934, 1937, 1938, 1943. Herre, 1936, 1940. Hildebrand, 1946. lehisa, 1939. June, 1952a. Thunnus — Continued Kawana, 1934, 1935, 1937, 1938. Kida, 1936. Kimura, 1932, 1933, 1935. Kimura and Ishii, 1932, 1933a. LeDanois, 1933. LUling, 1950, 1951, 1952a, 1952b. Maldura, 1946. Marukawa, 1939c. Mather, 1954. Mazzarelli, 1935. Migita and Arakawa, 1948. Mine and lehisa, 1940. Miyama and Osakabe, 1938, 1940. Molteno, 1948. Morice, 1953a, 1953b. Murayama and Okura, 1950, 1952. Murray, 1952. Nakamura, 1938, 1939a, 1939b, 1943, 1949, 1951. Nankai Reg. Fish. Res. Lab., 1951a. Navarro and Lozano, 1950. Navaz, 1950. Nigrelli and Stunkard, 1947. Nomura et al., 1952-53. Oita Pref. Fish. Expt. Sta., 1930. Okada and Matsubara, 1938. Okada et al., 1935. Okinawa Pref. Fish. Expt. Sta., 1940b. omori and Fujimoto, 1940. omori and Fukuda, 1938, 1940. Priol, 1944. Reiss and Vellinger, 1929. Rivas, 1951, 1953. Roedel, 1948a. Ros6n, 1943. Russell, F. S., 1933a, 1933b, 1934a, 1934b. Sanzo, 1932. Schaefer, 1948c, 1951. Schaeffers, 1952, 1953. Schultz, 1949. Schultz and DeLacy, 1936. Schweigger, 1949. Scordia, 1930, 1939a, 1939b, 1940, 1943. Sella, 1930, 1931, 1952. Serventy, 1941a. 1941b, 1942b, 1947. Shapiro, 1948a, 1948b. Shimada, 1951b. Shimizu, 1947. Society for the Promotion . . . 1936. Soldatov and Lindberg, 1930. Sugiura, 1932. Suyehiro, 1942. Takayama and Ando, 1934. Tanaka, 1931, 1939. Taranetz, 1937. Tauchi, 1940a. Tinker, 1944. Uda, 1932a, 1932b, 1935a, 1940b, 1952. Van Campen, 1952. Walford, 1931, 1937. BIBLIOGRAPHY ON THE TUNAS 247 Til iin nus — Continued Westman and Gilbert, 1941. Westman and Neville, 1942. Whitehead, 1930, 1931. Whitley, 1947. Wolfe Murray, 1932. Yabe et al., 1953. Thuntui^ alalunga. See Germo. Thunnus albacora. See N. macropterus. Thutinus germo. See Germo. Thunnus maccoyi Blackburn and Rayner, 1951. Boeseman, 1947. Dung and Royce, 1953. Godsil and HoUnberg, 1950. Nomura et al., 1952-53. Serventy, 1941a, 1941b, 1947. WhiUey, 1947. Thunnus macropterus. See N. macropterus. Thtmnus mebachi. See Parathunnus mebachi. Thunnus nicolsoyii Serventy, 1942b. Thunnus obesus. Fraser-Brunner, 1950. Thunytus orientalis Aikawa, 1933. Aikawa and Kato, 1938. Dung and Royce, 1953. Fisheries Society of Japan, 1931. Fowler, 1934. lehisa, 1939. June, 1952a. Kawana, 1934, 1935, 1937, 1938. Kida, 1936. Kimura, 1932. 1933, 1935. Kimura and Ishii, 1932, 1933a. Migita and Arakawa, 1948. Mine and lehisa, 1940. Miyama and Osakabe, 1938, 1940. Murayama and Okura, 1950, 1952. Nakamura, 1938a, 1939a, 1939b, 1943, 1949, 1951. Nankai Reg. Fish. Res. Lab., 1951a. Nomura et al., 1952-53. Oita Pref. Fish. Expt. Sta., 1930. Okada and Matsubara, 1938. Okada et al., 1935. Okinawa Pref. Fish. Expt. Sta., 1940b. omori and Ftijimoto, 1940. Omori and Fukuda, 1938, 1940. Shapiro, 1948a, 1948b. Shimada, 1951b. Shimizu, 1947. Society for the Promotion . . . 1936. Sugiura, 1932. Suyehiro, 1942. Takayama and Ando, 1934. Tanaka, 1939. Tauchi, 1940a. Tinker, 1944. Uda, 1932b, 1940b, 1952. Thunnus orientalis — Continued Van Campen, 1952. Yabe et al., 1953. Thuimus rarus. See Neothunnics varus. Thunnus schlegeli. See Thunnus orientalis Thunnus sibi. See Pai-athunnus sibi. Thunnus thunniiia. See Euthynnus alletteratus. Thunnus thunmis. See Thunnus thynnus. Thunnus thynnus Alaejos, 1931. Aricb and Genovese, 1953. Bahr, 1952. Barnhart, 1936. Bigelow and Schroeder, 1953. Bonamico, 1933. Brock, 1938, 1949. Cerquetelli, 1936. Chabanaud, 1930. Conseil Int'l pour 1' Exploration de la Mer, 1933. Crane, 1936. DeBuen, 1930, 1931, 1932, 1935, 1937. De La Tourrasse, 1951. Delsman, 1933. Dieuzeide, 1930, 1931. Dung and Royce, 1953. Ehrenbaum, 1934. Fick, 1937. Fish, 1948. Food and Agr. Organ. U. N., 1949b. Fowler, 1931, 1936, 1938, 1944. Frade, 1930a, 1930b, 1931a, 1931b, 1935, 1937a, 1937b. Frade and Managas, 1933. Fraser-Brunner, 1950. Fujii, 1932. Galtsoff, 1952. Genovese, 1952, 1953. Ginsburg, 1953. Godsil, 1949b. Godsil and Byers, 1944. Heldt, 1930, 1931a, 1931b, 1932b, 1934, 1937, 1938, 1943. Herre, 1936, 1940. June, 1952a. Kida, 1936. Kimura, 1932. LeDanois, 1933. Luling, 1950, 1951, 1952a, 1952b. Marukawa, 1939c. Mather, 1954. Mazzarelli, 1935. Molteno, 1948. Morice, 1953b. Murray, 1952. Navarro and Lozano, 1950. Navaz, 1950. Nigrelli and Stunkard, 1947. Priol, 1944. Reiss and Vellinger, 1929. Rivas, 1951, 1953. Roedel, 1948a. 248 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE Thunnus thynnus — Continued Ros6n, 1943. Russell, F. S., 1933a, 1933b, 1934a, 1934b, 1936. Sanzo, 1932. Schultz, 1949. Schultz and DeLacy, 1936. Scordia, 1930, 1939a, 1939b, 1940, 1943. Sella, 1930, 1931, 1932, 1952. Society for the Promotion . . . 1936. Soldatov and Lindberg, 1930. Tanaka, 1931. Taranetz, 1937, 1944. Uda, 1932a, 1935a. Walford, 1931, 1937. Westman and Gilbert, 1941. Westman and Neville, 1942. Whitehead, 1930, 1931. Wolfe Murray, 1932. Thunnus tonggol DeBeaufort and Chapman, 1951. Fraser-Brunner, 1950. Serventy, 1942b. Thunnus zacalles. See Kishinoella zacalles. Thynnus af finis. See Euthynnus allettei-atus. Thynnus alalonga. See Germo. Thynnus germo. See Germo. Thynnus maccoyi. See Thunnus maccoyi. Thynnus macroptertis. See N. macropterus. Thynnus orientalis. See Thunmis orientalis. Thynnus pacificus. See Germo. Thynnus pelamys. See KO'tsuwonus. Thynnus sibi. See Parathunnus sibi; also Germo. Thynnus Vumina. See Euthynnus alletteratus. Thynnus thunnina. See Euthynnus alletteratus. Thynnus thynnus. See Thunnus thynnus. Thynnus tonggol. See Thunnus tonggol. Tonno. See Thunnus thynnus. Tuna (otherwise unspecified) Aikawa, 1932. Anonymous, 1939b. Auffret, 1931. Bini, 1931, 1933. Chiba Pref. Fish. Expt. Sta., Katsuura Branch, 1941e. Corwin, 1930. DeBuen and Frade, 1932. Domantay, 1940. Farina, 1931b. Federation of Japan Tuna . . . 1951a, 1951b, 1952, 1953a, 1953b. Flett, 1944. Food and Agr. Organ. U. N., 1949a. Frade, 1932. Godsil, 1938c. Had2i, 1934. Hasegawa, 1937. Heldt, 1932a. Hirtz, 1933. Imai, 1950. Imaizumi, 1937. Tuna (otherwise unspecified) — Continued Imamura, 1953. Isawa, 1935. June, 1951a. Kafuku, 1950. Kanagawa Pref. Fish. Expt. Sta., 1951b. Kawana, 1935. Kimura and Ishii, 1931. Kodama, lizuka, £ind Harada, 1934. Kreutzer, 1951b. LeGall, 1934e, 1951. McKeman, 1953. Marr and Schaefer, 1949. Marukawa, 1939a. Matsui, K., 1942a. Matsui, Y., 1938. Meyer, 1951. Mie Pref. Fish. Expt. Sta., 1950a, 1950b. Morovid, 1950. Murphy and Niska, 1953. Murphy and Shomura, 1952, 1953a, 1953b. Nishikawa, 1934. Niska, 1953. Niwa, 1937. Noguchi, 1938. Okumura, 1943. Postel, 1949. Rasalan, 1950. Rawlings, 1953. Ronquillo, 1953. Rosa, 1950. Saito, 1937. Sakai and Uno, 1940. Scordia, 1940. Sella, 1932. Sette, 1954. Shapiro, 1950. Shimada, 1951a. Society for the Promotion . . . 1937b. goljan, 1930. South Seas Gov't. . . . 1937b, 1941a. Tanaka, 1935, 1936. Tester et al., 1952. Thiel, 1938. Tomiyama, 1933. U. S. Fish and Wildlife Service Vitlov, 1949. Wilson, 1953. Zei, 1948. Wanderer Whitley, 1937. Weather correlated with fishing or distribution Murphy and Niska, 1953. Murphy and Shomura, 1953b. Yellowfin tuna. See Neothunnus macropterus. Young Bini, 1952. BIBLIOGRAPHY ON THE TUNAS 249 Young — Continued Delsman, 1931. Delsman and Hardenburg, 1934. Eckles, 1949b. Greenhood, 1952. Hatai et al., 1941. Herald. 1951. Inanami, 1942d. Kimura and Ishii, 1931. LeDanois, 1951. LeGall, 1949. Marr, 1948. Marukawa, 1939b. Young — Continued Sanzo, 1932, 1933. Schaefer, 1948c. Schaefer and Marr, 1948a, 1948b. Sette, 1954. Shimada, 1951b, 1951d. Suda, 1953. Uchida, 1937. Wade, 1949, 1950a, 1951. Yabe, 1953. Yabe et al., 1953. Yabe and Mori, 1948. 02' S. 2°07' N. 1°19' S. 2-54' N, 1°04' N. 4°04' N. 2°56' S. 3°49' N. 4°04' N. 4°04' N. 3°49' N. 6°08' S. 4°04' N. 4°C4' N, 4°04' N. 4°04' N. 4°04' N. 1°20' S, 1°59' N. 1°20' S. 1°20' S, 1°20' N. r20' S, 1°69' N, 1°69' N. 1°69' N. 1°67' N. r59'N. 1°20' N. 1°59' N. 1°20' S. 1°57' N. 1020' S. 1°59' N, 1°59' N. 1°20' S, 2°46' N. 1°59' N. X'iT N. 1°59' N. 3°51' N. 1°59' N. 2°42' N, 1°57' N. 1°69' N. 2°42' N. l-S?' N. 1°69' N, 3''52' N. 3°6r N. 1°59' N. 0°22' S. 154°56' W. 154°59' VV. 154°59' VV. 154°56' W. 156''41' VV. 156°41' VV. 162°19' VV. 162°19' VV. 162°Q6' VV. 162°06' VV. 162°06' VV. 168°17' VV. 168°21' VV. 161°15' VV. I71°05' VV. 171°31' VV. 171°05' VV. 171°05' VV. 171°16' VV. 150°00' VV. 150°09' VV. 1.54°,57'VV. 150°36' VV. 150°11' VV. 150°09' VV. 150°11' VV. 150°24' VV. 150°09' VV. 150°09' VV. 150°11' VV. 150°11' VV. 150°24' VV. 154°57' VV. 160°19' VV. 150°24' VV. 154°57' VV. 150°09' VV. 150°24' VV . 150°19' VV . 151°06' VV. 154°66' VV. 150°08' VV. 150°07' VV. 154°56' VV. 154°66' VV. 150°07' VV . 150°09' VV. 154''66'VV. 164°56' VV. 154°56' VV. 164°56' VV. 154°56' VV. 156°06' VV. 167°31' VV. 165°06' VV. 165°06' VV. 155°03' VV. 155°0C' VV. 157°31' VV. 157°31' VV . 157°31'VV. 167°32' VV. 167°31' VV. 155°03' VV. 167°31' VV. 166°06'W. 167°32' VV. 156°06' VV. 157»31' VV. 157°31' VV. 155°06' VV. 155°10' W. 157°31' W. 157°32' VV. 157°31' W. 159°26' VV. 157°31' VV. 165°05' W. 157°32' VV. 167°31' W. 165°05' VV. 167°32'W. 157°31' W. 159°20' VV. 159°26' VV. 157°3I' VV. leo-or VV. M Im Im Im M In In In In Im Im Im Im Im In In Im Im Im M M M M M M M M M M M M M M In In In In In In In In In In In In Im Im Im Im Im Im Im M M M M M M M M M M M M M M In In In In In In In In In In In In In In In In In In Im Im Im Cm. 113 104 96 78 143 146 135 132 127 133 119 85 83 66 98 93 91 78 68 149 148 147 146 145 143 143 143 139 138 138 138 137 135 152 150 148 or 140 142 142 141 141 140 138 136 129 128 140 136 126 123 lis 114 108 148 148 147 143 142 139 139 138 134 133 130 126 124 76 142 140 140 138 137 136 136 135 136 134 133 132 131 131 130 130 130 98 123 120 112 Feb. 10, 1951--- 0°22' S. 3°51' N. 3°51' N. 1°69' N. 0°22' S. 5°53' N . 0°22' S. 5°63' N. 3°52' N. 5°53' N. rei'N. 3°62' NT. 3°62' N. 5°63' N. 3°52' N. 1°51' N. 4°30' S. 3°07' S. 2°60' S. 3°15' S. 4°30' S. 3°07' S. 0°02' N. 0°02' N. 2''39' .?. 4°03' S. 2°39' S. 4°03' S. .3°00' N. 1°18' S. 1°I8' S. 6°47' S. 8°00' S. 1°00' N. 1°00' N. 1°51' S. I°48' S. TOO' N. l^OO' S. 1°00' N. 4°12' N. 0°09' N. 0°09' N. 6°16' S. 1°00' S. 1°00' S. 3°07' N. 2°12' N. 3°25' S. 0°09' N. 2°12' N. 3°07' X. 1°48' S. 1°00' S. l°0O' N. 1°00' N. 4°12'N. 4°12' N. 2°I2' N. 2°12' .M. 3°07' N. C°09' N. 6°16' S. 1°0()' S. I°51' S. 3°07' N. 2°12' N. 4°12' N. 13°31'S. 13''31' S. 4''10'N. 6°40' S. 6°40' S. 1°20' S. 6°18' S. 1°20' N. o'or N. l'=20' .S. 2°50' N. 2°50' N. 6°40' S. 0°01' N. 2°43' S. l'>20' N. 2°50' N. 4''02' S. 1°61' N. lecoi' W. 159°26' W. i59°26' v^^ 157°31' W. i6o°or w. 162°05' VV. 160°01' VV. 162°05' VV. 169°20' VV. 162°05' VV . 167°20' VV. 159°20' W. 169°20' VV. 162°06' W. 159°20'VV. 157°20' W. 172°10' W. 171°05' VV. 171°40' W. 171°30' VV. 172''10' W. I71°05' VV. 179°48' E. 179°48' E. 179°54' E. 179°58' E. 179°64' E. 179°68' E. I80°00' 180°00' 180°00' 179°59' VV. I79°56' E. 140°00' VV. 140°00' W. 140°11' VV. 139°69' VV. 140°00'VV. 140°05' VV. 140°0O' VV, 140°20' W. 139°47' VV. 139''47' VV. 141°32' W. HOBOS' VV. 140°05' W . 140°07' VV. 140°18' W. 140°03' W. 139<'47' VV. 140°18' W. I40°07' VV. 139°59' VV. 140°05' W. 140°00' VV. 140°00' W. 140°20' W. 140°20' VV. 140°18' VV. 140°18' VV. 140°07' W. 139°47'VV. 141°32' VV. 140°05' VV. 140°11' VV. 140°07'VV. 140°18' VV. 140°20' VV. 147°08' VV. 147°OS' VV. 168°30' VV. 169°03'W. 169°03' VV. 169°00' VV. 169°03' W. 169°05' W. 169°04' VV. 169°00' VV. 169°07' VV. 169°07' VV. 169°03' VV. 169<'04' W. 169°00' W. 169''05' VV. 169°07' VV. 169°04' W. 157°2n' \V. Im Im Im Im Im Im Im Im Im Im Im Im Im Im Im Im M M Im Im Im Im M M M M M M M M M In In R R R M M M M M M M M M M M M M M -M M M M M M M M M M M M M M M M M In M Im R M M M M M M M M M M M M M In In M Cm. IK Jan. 27, 1951 Feb. 5, 1953 Do 10" Do --- lOi Jan 26, 1951 Feb. 3, 1963.. 10^ Jan. 31, 1953 Feb. 16, 1961 Feb. 21, 1951 Feb. 11, 1951... 9 Do Jan. 23, 1953 9( 8f Do _-. Feb. 21, 1961 .- 8> Jan. 25, 1953 Feb. 4, 1951.. 8; Do.--- -- Do Feb. 21, 1951...- -.- Feb. 16, 1951 Feb. 17, 1951 8 Jan. 21, 1951 7 Jan. 19, 1951 Feb. 19, 1961 Feb. 22, 1961. Jan. 27, 1953 Jan. 26, 1951- Jan. 31, 1951 Feb. 12, 1951 Feb. 13, 1951. 7 7 Jan. 26, 1951 Do Feb. 8, 1950 Feb. 5, 1951 Feb. n, I960. 12( 10 Jan. 29, 1961 . 12 Feb. 11, 1953.- - Feb. 10,1962 Feb. 8, 1950 -.- Feb. 5, 1951 Feb. 18, 1952 Do Feb. 20, 1952 Feb. 21,1952-- - Feb. 20, 1952 Feb. 21,1962 Feb. If), 1952 Feb. 19, 1952 Do -.. Feb. 23, 1962 - Feb. 24, 1962 Mar. 15, 1953 Do Mar. 12, 1963--- Mar. 11, 1963 _. Mar 15, 1953 8( Feb. 4, 1953 Feb. 4, 1952-.- Feb. 14, 1953 - Feb. 12, 1953 7 6 14 14 Feb. 4, 1953 Feb. 12, 1953 14 I4( Feb. 13, 1953-- 13 Feb. 4, 1953 Do 13 13 Feb. 12, 1953-.- Do 13 12 Feb. 13,1963 Feb. 4, 1952 Feb. 3, 1953 13 13 14 Feb. 13, 1953 14 Feb. 4, 1952 14 Feb. 4, 1953 16 Feb. 13, 1953 15 Feb 3, 1963 Mar. 13, 1953 Mar. 16, 1953-- Mar 18, 1963 16 Feb. 10, 1953 . . 14 Feb. 1, 1962 14 Feb. 17, 1953 Mar 14 1963 14 Feb. 2, 1953 Do Mar. 8, 1953 14 Feb. 1, 1952 14 Do Mar 13 1953 14 Feb. 2, 1953 Do 14 Feb. 19, 1963 Mar 17 1963 14 Feb. 1, 1952 Mar 16, 1953 14 Do Mar 10 1963 14 Do - 14 Do Mar 16 1953 14 Do Mar. 17, 1953 Mar. 11,1963.-- --- Mar. 13, 1963 14 Feb. 6, 1962 14 Feb. 3, 1963 14 Feb. 5, 1952 14 Do Do 14 Feb. 3, 1962 Mar. 18, 1953 Do Mar. 16, 1953 Do 14( Feb. 5, 1952 141 Feb. 3, 1953 13 Do --_ -- 13 Do Mar 17 1953 13 Feb. 1, 1953 _-- 13 Feb. 3, 1953 Mar 8 1953 13 Feb. 3, 1952 __- 13 Feb. 3, 1953 Mar 12 1953 13 Feb. 5, 1952 13 Feb. 1, 1953 Mar 16 1953 13 Feb. 5. 1952 Mar. IS, 1953 Mar 4, 1953 . - - 14 Feb. 3, 1953 ,-- 14 Do -„ Do 7 Feb. 5, 1952 14 Feb. 2, 1962 Mar 4 1952 14 Feb. 3, 19.53 Do 14 Feb. 1, 1953 Mar 8 1952 14 Feb. 3, 1953 14 Feb. 5. 1963 -- Mar 10 1952 14 Feb. 3, 1953-- 14 Feb. 6, 1952 Mar 8 1952 14 Feb, 1, 1963-- 14 Feb. 3, 1963-- -- Do 13 Feb. 6, 1952- - 13 Feb. 1, 1953 Mar 9 1952 13 Feb. 3, 1963 - -... 13 Feb. 4, 1961 Mar 10 1952 13 Feb. 5, 1953- Mar. 11, 1952 - Mar fi 1952 14 Feb. 3, 1953 12 Feb. 11,1951 Apr. 30, 1951 - 11 SPAWNING OF YELLOWFIX TUNA 253 T.VBLE 1. — Daln on 7/,0 i/ellowfin tuna specimens from the central equatorial Pacific for which matiirilij determinalions were made in the laboratory — Continued Date Position Stage of maturity Fish length Cm. 98 108 96 96 81 110 104 98 98 98 92 90 80 80 80 75 70 148 146 146 135 151 146 146 143 140 140 136 136 134 133 133 130 129 129 127 123 122 121 117 114 106 101 100 92 92 86 128 122 121 118 117 115 115 114 110 109 108 107 106 104 104 100 lOO 98 98 94 92 90 90 89 88 88 88 85 82 149 115 112 111 111 108 104 103 102 101 101 101 100 96 Date Position Stage of maturity Fish Latitude Longitude Latitude Longitude length Apr.26.1951. Anr 27 1 951 1°51' N. I'sr X, \'sy X. I'si'x. I'Sl' X. s-ss' X. 5°53' X. 0°22' S. 5''53' X. 5°53' N. 5°5.3'X, 5°53' X. psr N. 1''51' X. 1°51'X. i°5rx. S-SS'X. 7°09' X. 4''18' X. 4°18' X. 4°18' X. 4°55' X. 4°02' X. 4°02' X. 4°02' X. 4°55' X. 3''58' -V. 3''52' X. 1°51'X. 4°45'X. 4°55' X. 4'>52'X. 6'>02'X. 5<>26'X. 4°.55' X. 6''25'X. 4°56' X. 4°45' X. 4°17' X. 4°02' X. 4°17' X. 6°25' X. 6-25' X. 6°25' X. 6°25' X. 6'>25' X. 1°51' X. 4°52' X. 4°02' X. 4°45' X. 5°,53'X. 3''58' X. 4°42'X. 6''25'X. 3°58' X . 4<'17'X. 6°25'X. 3''58' X. 1°51'X. 5°58' X. 5-53' X. 3° 58' X. 1°51' X. 6°25' X. 1°51' X. 3°58' N. 6°25' X. fi°25'X. 6°25'X. 6°25' X. 6°25' X. 6''25' X. 6°25'X. 6°25'X, 6°25' X. 6''25' X. S'SS' X. 6°25' N . 5'>53' X . 4''42' X. 5°58' X. 4°42' X, 4°42' X. 3°58' N. 4''02' X. 5'>S8' X. 4°02' X. 3"'68' X. 6°58' X. 6''25' X. 157°20' W. 157020' W. 157°20' W. 157°2fl' W. 157''20' W. 162°05' W. 162''05' W. 160°01' \V. 162°05' W. 162°05' W. 162°05' \V. 162°05' W. 157°20' W. 157°20' W. 157-20' W. 1.57°20' W. 162°05' W. 119°00' W. 119"'35'W. 119''35' W. 119°35' \V. 161''19' W. 159''34' W. 159°34' W. 169''34' \V. 161°19' W. 159°04' W. 159°20' W. 157°20'\V, 160°11' W. 161°19' W. 1.59°35' W. 162°28' W. 161°37' W. 16ri9' W. 162''26' W. 160°32' W. 160°11' W. 160°28' W. 159-34' W. 160-28' W. 162-26' W. 162-26' W. 162-26' \V. 162-26' W. 126-26' W. 157-20' W. 159-35' W. 159-34' VV. 160-11' W. 162-05' W. 159-04' W. 160-24' W. 162-26' W. 159-04' W. 160-28' W. 162-26' W. 159-04' W . 157-20' \V. 162-52' \V. 162-05' W. 159-04' W . 157-20' W. 162-26' W. 157-20' W. 159-04' W. 162-26' W. 162-26' W. 162-26' W. 162-26' W. 162-26' W. 162-26' \V. 162-26' \V. 162-26' VV. 162-26' \V. 162-26' W. 162-52' W. 162-26' W. 162-05' W. 160-24' W. 162-52' W. 160-24' W. 160-24' \V. 159-04' W. 1.59-34' W. 162-52' W. 159-34' W. 159-04' W. 162-52' W. 162-26' W. M In In In In Im Im Im Im Im Im Im Im Im Im Im Im R M M M M M M M M M M M M M M M M M M M M M M M M M M M M M In In In In In In In In In In In In In In In In In In In In In In In In In In In In In Im Im Im Im Im Im Im Im Im Im Im Im Im Ira Mav 28. 1954 Mav 30, 1951 4''02' N. 6-25' N. 6-26' X. 4-56' X. 6-25' X. 6-25' X. 6-25' X. 6-25' X. 6-25' N. 1-51' X. 1-51' X. 1-61' X. 1-51' N. rsi' X. 3-52' X. 4-42' N. 6-25' X. 6-25' X. 5-53' X. 6-25' X. 4-26' S. 3-27' S. 6-51' S. 4-26' S. 4-26' S. 4-26' S. 4-26' S. 6"'41' S. 4-26' S. 4°26' R. 0-19' X. 6-06' X. 2-19' X. 6-06' X. 8-00' X. 6-06' N. 8-00' X. i-or s. 0-21' X. 2-19' X. 2-19' X. 2-19' X. 6=25' X. 1°,52' .X. 2-29' X. 3-04' X. 1-47' X. 3-04' X. 2-29' N. 1-52' X. 6-25' X. 4-42' X. 6-25' X. 6-53' N. 5-53' X. 5-53' N. 1-47' X. 3-04' N. 1-52' N. 2-03' X. 2-03' X. 3-04' X. 4-42' N. 2-or N. 2-03' X. 2-or X. 1-52' N. 4-42' X. 2-01 ' X. 3-52' X. 3-52' X. 3?52' X. 4-42' X. 3-52' X. 3-52' X . 3-52' X. 5-53' X. 5-53' X. 5-53' X. 5-53' X. 0-30' S. 2-14' S. 0-30' S. 0-30' S. 0-30' S. 2-14' S. 0-30' S. 2-14' S. 2-50' S. 2-50' S. 159-34' W. 162-26' W. 162-26' \V. 160-32' W. 162-26' VV. 162-26' VV. 162-26' VV, 162-26' VV. 162-26' VV. 157-20' VV. 157-20' VV. 157-20' VV. 157-20' VV. 157-20' VV. 159-20' VV. 160-24' VV. 162-26' VV. 162-26' VV. 162-05' VV. 162-26' VV. 170-09' VV. 170-12' VV. 170-02' VV. 170-09' VV. 170-09' VV. 170-09' VV. 170-09' VV. 169-44' VV. 170-09' VV. 170-09' VV. 119-58' VV. 129-55' VV. 130-07' VV. 129-55' VV. 130-24' VV. 129-55' VV. 130-24' VV . 125-56' VV. 129-23' VV. 130-07' VV. 130-07' VV. 130-07' VV. 162-26' VV. 156-47' VV. 158-22' VV. 1.59-13' VV. 158-16' VV. 1,59-13' VV. 158-22' VV. 156-47' VV. 162-26' VV. 160-24' VV. 162-26' VV. 162-05' VV. 162-05' VV. 162-05' VV. 158-16' VV. 159-13' VV. 156-47' VV. 157-40' VV. 157-40' VV. 159-13' VV. 160-24' VV. 157-09' VV. 157-40' VV. 157-09' VV. 156-47' VV. 160-24' VV. 1.57-09' VV. 1.59-20' VV. 159-20' VV. 159-20' VV. 160-24' VV. 1,59-20' VV. 159-20' VV. 1,59-20' VV. 162-05' VV. 162-05' VV. 162-05' VV. 162-05' VV. 169-52' VV. 170-00' VV. 169-52' VV. 169- .52' VV . 169-.52'VV. 170-00' VV. 169-52' VV. 170-00' VV. 171-40' VV. 171-40' VV. Im Im Im Im Im Im Im Im Im Im Im Im Im Im Im Im Im Im Im Im R M M M M M M M t'" Im M R R R R R R M M M M Im R M M M M M M M M M M M M M In In In In In In In In In Im Im Im Im Im Im Im Im Im Im Im Im Im Im Im R M M M M M M M Im Im Cm. 93 90 Do Mav 20, I95I 88 Apr 30, 1951 Mav 24, 1954 May 30, 1951 88 Anr 26 1 951 88 Do 87 Anr 16 195! Do - 86 Apr. 11, 1951 Do - May 31, 1951.. 86 85 Apr. 16. 1950 - \pr 15, 1951 May 1,1951 Do Do 83 82 \nr 16 1951 81 Do 80 Apr. 26. 1951 Apr 27 1951 Do 80 May 7, 1951 79 Anr 26 1951 May 3, 1950 -- . 75 \Dr 13 1951 May 11, 1951 75 May 29. 1952 Do May 27, 1950 Do 75 Mav 31, 1952 74 Do 74 Do Mav 30, 1953 134 Mav 23, 1954 May 31,1953 May 28, 1953 149 Mav 28, 1954 148 Do -.- Mav 30, 1953 144 Do "Do 136 Mav 23, 1954 Do 136 Mav 30 1954 Do 133 Mav 7, 1951 May 29, 1953 103 Mav 13, 1950 -- Mav 30, 1953 130 Mav 25, 1954 Do 94 Mav 23, 1954 June 3, 1952 - June 12 1952 157 Mav 26, 1954 156 Mav 18, 1954 June 9, 1952 150 Mav 22, 1954 June 12, 1952 - 142 Mav 23, 1954 June 13, 1952 139 Mav 31, 1951 - June 12, 1952 129 May 24, 1954 June 13 1952 94 Mav 25, 1954 --- 153 Mav 27, 1954. June 8, 1952 - 153 Mav 28, 1954 June 9 1952 146 May 27, 1954 Do 135 Mav 31, 1951 Do 142 Do. ..:.: 90 Do June 7 1954 152 Do. June 2 1954 147 Do June 1 1954 146 Mav 1, 1951 Tune 9 1954 142 May 26, 1954. 140 Mav 28, 1954 --- 138 Mav 25, 1954... 126 May 28, 1950. June I. 1951 118 Mav 30, 1954 , June 5, 1950 " -.- 99 May 3, 1950. .- 90 Mav 31, 1950 Do 87 May 30, 1954 Do. 84 Mav 27, 1954-- Do 83 Mav 29, 1950 128 Mav 30, 1954 Tune 1 1954 118 May 12, 1950 June 7, 1954 115 May 17, 1954 June 4, 1954... Do 114 May 11, 1951 112 May 30. 1954 no May 1. 1951 June 4 1950 no Mav 31, 1951 Junes, 1954 108 Mav 1. 1951 __.. June 4, 1954 IOC May 30, 1954 June 8 1954 12C Mav 30, 1951 _.. June 7, 1954 no May 12, 1951 June 4, 1950 IOC May 30, 1951 Junes. 1954 94 Mav 31. 1951 Tune 6 1951 85 May 30. 1951. Do 83 Mav 31. 1951 Do 83 Do June 4. 19.50 82 Do 82 May 28, 1950 Do 82 May31,I951 Do 8C May 17, 1954 June 1 1951 77 May 31, 1950 Do 76 May 27, 1950. May 3, 1950 Do 76 June 3 1950 75 May 17, 1954 June 2. 19,53.-- June 1 1953 138 May 3. 1950 142 1)0 Mav 30, 1954.. May 28, 1954. Mav 17, 19.54. May 28. 19.54 May 30, 19.54 May 17. 19.54 Mav 3(1, 1961 ... June 2. 1953.-- Do Do June 1. 1953 141 133 131 129 June 2. 1953 June 1. 1953 121 102 June 12. 1951 135 June 17. 19.51 122 254 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE Table 1. — Data on 740 yellowfin tuna specimens from the central equatorial Pacific for ivhich maturity determinations were made in the laboratory — Continued Date June 17, 1951- June 1. 1953- . Julv 17, 1950- July 15, 1950- July 19, 1950-. Do Aug. 24, 1952- Aug. 23, 1952. Aug. 24, 1952- Aug. 31, 1952- Aug. 2(;, 1952, Aug. 31, 1952- Aug. 2«, 1952- Aug. 24, 1952- Aug. 21, 1952- Aug. 23, 1952. Aug. 28, 1952- Aug. 29, 1962- Aug. 27, 1952- Aug. 31, 1952. Aug. 2fi, 1952- Aug. 29, 1962- Aug. 13, 1953- Do Do. Aug. 27, 1961. Aug. 13, 1953. Do Do Aug. 26, 1953. Aug. 16, 1953. Aug, 12, 1953. Aug. 19, 1953. Aug. 7, 1953.. Do Aug. 21, 1953. Aug. 25, 1953. Aug. 7, 19,i3-. Aug. 20, 1963- Aug. 21, 1953 Do Do Do Aug. 19, 1953- Aug. 25, 1953- Aug. 7, 1953- - Aug. 12, 1953- Do Aug. 19, 1963- Aug. 20, 1953- Aug. 7, 1953.- Do Aug. 12, 1953- Aug. 14, 1953. Aug. 19, 1953- Aug. 23, 1953. Aug. 7. 1953.- Do- Aug. 26, 1960- Aug. 14, 1953. Aug. 19, 1963- Aug. 14, 1963- Aug. 16, 1953- Aug. 14, 19.53- Aug. 18, 1953. Aug. 19, 1953. Do Aug. 14, 19.53. Aug. 18, 1953. Aug. 14, 1953. Aug. 21, 1953. Aug. 19, 1953. Aug. 21, 1953. Aug. 16, 1953- Aug. 18, 1953. Aug. 20, 1953. Aug, 21, 1963. Aug. 14, 1953. Aug. 25, 1953. Aug. 18, 1953. Aug. 16, 1960 Do Aug. 17, I960. Do- Do Sept. fi, 1952. Sept. 9, 19.52. Sept. 7, 1952. Sept. 9, 1952. Do Latitude Longitude a'sn' R. 2"! 4' s. 2",50' s. 2''.50' s. 2°.5n' s. 2"50' s. 4-28' N. ,6"16' N 4°28' N. 3"45' N. 2"23' N. 3''45' N. ron' N. 4°2R' N. 7''02' N. ,5-16' N i°on' N. 2"no' N. r33' N. 3"45' N. 2°23' N. 2''no' N. 0"flS' N. n"08' N. 0"0S' N. 9",36' N. flans' N. o"n8' N. n"08' N. 7''.5()' N. 4°10' ,S, 1»21' N 1°31' S. 2"n5' N. 2''n6' NT. rir N. B-IO' NT. 2"06' N. cor N, rii' N. i"ii' N. i"ii' N. i"n' N. r3i' S. 6''l(l' N. 2"05' N. 1-21' N. 1"21' N. 1"31' S. O^fll' N. 2"n5' N. 2"05' N. r2i' N 1°0S' S. r.3i' K. 3"22' N. 2''05' N. 2°06' N. (,"?.!<' N. IW S, rm' S. 1"08' s. 4"10' s. I'-OS' 8. 2''.56' K, 1°3I' S. rsi S, ro8' s. 2".56 s 1°08 R. rii' N. rsi' S. rn N. 2°.33 R 2°,56 R 0°01 N. ni N, rns S. 6°10 N. 2"5B H. a-ss R, a'-as W. 3''07 S, 3"n7 S. 3''07 S. 2-06 N. 2"33 N. 1''42 N. 2°33 N. 2°33 N. 171°40'W. 170°00' W. 171''40' W. 171°40' W. 17r40' W. 171''40' W . 139''51' W. 140°28' W. 139°61' W. 140°10'W. 140° 12' W. 140°10'W. 140°22' W. 139°61' W. 140°46' W. 140°28' W. 140°22' W. 140''40'W. 140°13' W. 140°in' W. 140°12' W. 140°40' W. 164°51' W. 154°51' W. 154°51' W. 150°06' W. 154°61' W. 154°5I' W. !54°61' W. I59°24' W. 1.55°33' W. 165''16' W. 159°63' W. 157°.'i8' W. 157°38' W. 160°08' \V. 160°02' W. 157°38' W . 159°56' W. 160''08' W. 160"'08' W. 160°08' W. 160°08' W. 159°53' W. 160°02' W . 167°38' W. 155°16' W. 155'>16' W. 159''53' W. 169°56' W. 167''38' W. 167°38' \V. 1.55°16' \V. 155°18' W. 169°.53' W. 160°24' \V. 157''38' W. 167''38' W. 162°26' W. 1.55°18' W. 169°53' W. 155°18' W . 1,55''33' W, 156°18' W . 160°14' W. 1.59°53' W. 159°63' W. 165''18' W. 160°14' \V. 15.5°18' W. 160°08' W. 159°53' W. lecos' W. 155''23' W. wo'ir W. 159°66' W. 160°08' \V. 155°18' \V. 160°02' W. 160°14' W. 171°31' W. 171°31' W. 171°0j' W. 171°06' W. 171°06' W. 140°.56' \V. 143°22' W. 141°24' W. 143°22' W. 143°22' W. Stage of maturity Im Im M M In Im M M M M M M M M M M In In In In In In M M M M M M M M M M M M M M M M M M M M M M M M M M M M M M M M M M M M M In In In In In In In In In In In In In In In Im Im Im Im Im Im M Im Im Im Im R R M M M Fish length Cm. 118 81 140 128 134 118 166 151 151 151 146 143 139 129 124 121 157 153 or 139 147 142 141 139 168 143 143 143 or 131 142 141 138 153 151 148 144 143 142 142 142 141 141 141 141 140 140 139 139 138 136 136 136 136 135 135 135 134 134 128 126 124 111 147 142 140 139 138 138 138 136 134 132 131 127 125 111 89 139 116 109 104 102 89 118 114 86 66 64 165 136 153 148 147 Date Sept. 3, 1952 Sept. 6, 19.52 Sept. 7, 1952 Do Sept. 2, 1962 Sept. 6, 19.52 Sept. 2, 1952 Sept. 4, 1952 Sept. 7, 1952 Sept. 1, 1952 Sept. 2, 1952 Sept. 4, 19.52- Sept. 5, 1951 Sept. 13, 1952 Sept. 2, 1951 Sept. 13, 1952 Sept. 16, 1952 Sept. 4, 1951 Sept. 16, 1952 Sept. 19, 1951 Sept. 3, 1951 Sept. 19, 1961 Sept. 3, 1961- Sept. 18, 1961 Sept. 19, 1961 Sept. 20, 1951 Sept. 3, 1961 Sept. 19, 1961 Sept. 3, 1961 Do Sept. 4, 1951 Sept. 6, 1951 Sept. 19, 1951 Sept. 4, 1951 Do Sept. 17, 1951 Sept. 18, 1951 Sept. 19, 1951 Sept. 2, 1961 Sept. 3, 1951 Sept. 5, 1951 Do- Sept. 19, 1951 Do Sept. 20, 1951 Sept. 2, 1961 - Sept. ,5, 1951 Sept. 19, 1951 Do Sept. 2, 1951 Do Sept. 3, 1951 Sept. 19, 1951 Do Sept. 20, 1951 Sept. 2, 1951 Do Sept. 3, 1951 Sept. 5, 1951 Sept. 13, 1952 Sept. 17, 1951 Sept. 19, 1961 Sept. 20, 1961 Sept. 4, 1951- Sept. 6, 1951 Do Sept. 18, 1951 Sept. 2, 1951 Do Sept. 5, 1951 Sept. 16, 1962 Sept. 2, 1961 Sept. 3, 1961 Sept. 18, 1951 Sept. 3, 1951 Sept. 6, 1961 - Do Sept. 3, 1951 Sept. 4, 1961- Sept. 5, 1951 Sept. 6, 1951 Sept. 2, 1961 Sept. 17, 1952 Sept. 4, 1961 Sept. 3, 1951 Sept. 18, 1961 Sept. 17, 1951 Sept. 19, 1951 Sept. 17, 1951 Sept. 19, 1951 Latitude Longitude 4°04' N. 2°06' N. 1''42' N. r42' N. 3°05' N. 2°06' N. 3''05' N. 3°20' N. 1°42' N. 3°3r N. 3°05' N. 3''20' N. 2°02' N. 1°22' N. 4°04' .Nf. 1°22' N. 2''28' N. r59' N. 2°05' N. 2°00' N. 2°57' N. 2°00' N. 2°57'N. 2°02' N . 2°00' N. 0''54'N. 2°57' N. 2'>00' N. 2°.57' N. 2°67' N. 1°59' N. 2''03' N. 2°00' N. 1''59' N. 1°59' N. 2°or N. 2°02' N. 2°00' N. 4°04' N. 2° 57' N. 2°02' N. 2°02' N. 2°00' N. 2°00' N. 0''64' N. 4°04' N. 2°02' N. 2°00' N. 2°00' N. 4°04' N. 4°04' N. 2"57'N. 2°00' N. 2°00' N. 0°54' N. 4°04' N. 4°04' N. 2° 67' N. 2°02' N. 1°22' N. 2''01' N. 2°00' N. 0''54' N. 1°59' N. 2°03' N. 2''03' N. 2''02' N. 4°04' N. 4°04' N. 2'>02' N. 2°28' N. 4''04' N. 2°57' N. 2<'02' N. 2°57' N. 2°02' N. 2°02' N. 2°57' N. 1°59' N . 2°02' N. 2°03' N. 4<'04' N. 3°26' N. 1°59' N. 2°57' N. 2°02' N. 2°or N. 2°00' N. 2°01' N. 2''00' N. 140°09' W. 14n°66' W. 141°24''W. 141°24' W. 140°02' W. 140°56' \V. 140°02' W . 140°10' W. 141°24' W. 140"'28' W. 140°02' W. 140°10' W. 151°50' W. 149''.54' W. 150°06' W. 149°54' \V. 150°38' W. 150°12' W. 150°23' W. 15I°24' W. 150°17' W. 151°24' W. ISO'l?' W. 153-12' W. 151°24' W. ISO^OO' W. 150°17' W. 151°24' W. 150°17' W. 150°17' W. 150°12' W. 153°12' W. 151°24' W. 150"'12' W. 150°12' W. 154'>50' W. 153°12' W. 151°24' W. 150°06' W. 150°17' W. 151''60' W. 151°60' W. 151°24' W. 151°24' W. 160°00' W. 160°06' W. 151°60' W. 151°24' W. 15r24' W. 150°06' W. 150°06' W. 150°17' W. 161°24' W. 15r24' W. 150°00' W. 150°06' W. 150°06' W. 150°17' W. 151°50' W. 149°54' W. 154°50' W. !5r24' W. 1,50''00' W. iso'iy W. 153°12' W. 163°12' W. 153°12' W. 150°06' W. 150°06' W. 161°50' W. 160°38' W. 150°06' W. 160°17' W. 153°12' W. 150°17' W. 151°50' W. 151°50' W. 160°17' W. 150°12' W. 161='50' W. 153°12' W. 150°06' W. I51°40' W. 150°12' W. 150°17' W. 153''12' W. 154° 50' W. 151°24' W. 164°50' W. 161°24' W. Stage of maturity M M M M In In In In In In In Im R R M M M M M M M M M M M M M M M M M M M M M M M M M M M M M M M M M M M M M M M M M M M M M M M M M M M M M M M M M M M M M M M M M M M M M M M M M In In In SPAWNING OF YELLOWFIN TUNA 255 Table 1. — Data on 740 yellowfin tuna specimens from the central equatorial Pacific for which maturity determinations were made in the laboratory — Continued Date Position Stage of maturity Fish length Date Position Stage of maturity Fish Latitude Longitude Latitude Longitude length Sept 22, 1951 1°07' S. 2°01' N. 2°01' N. 2°01' N. 2°01' N . 2°00' N. 2°01' N. 2°01' N. 0°54' N. 2°00'N. 2°01' N. 1°59'N. 2°01' N. 4°56' S. 2°01'N. 2°01' N. 2°02' N. 2°or N. 4°04' N. 4°56' S. 4°56' S. r52' N. 1°19' N. 1°52' N. 1°52' N. 1°52' N. 1°59' N. r52'N. 2°02' N. 2°02' N. 1°52' N. 2°02' N. 1°52' N. 2°02' N. 2°02' N. 2°02' N. 1°52' N. 2°02' N. r62' N. 1°19'N. 2°02' N. 1°59' N. 1°59' N. 1=59' N. 1°59' N. 1°59' N. 8°14' N. 3°58' S. 5°36' S. 5°34' N. 3°12' N. 5°34' N. 2°15' N. 5°34' N. 2°15' N. 5°34' N. 4°00' N. 7°17' N. 6°25' N. 6°25' N. 6°25'N. 6°25' N. 7°33' S. 7°33' S. 7°33' S. 7°33' S. 7°33' S. 3°11'S. 3°irs. 1°00' N. 1°00' N. 2°13' N. 6°53' N. 6°13' N. 6°59' N. 7°24' N. 6°25' N. 7°24' N. 3°52' N. 6°13' N. ri2' N. I'Sl'N. 3°52' X. 3°.52' N. 6°13' N. 2''55' N. 2°.55' N. 1°12' N. 150°21' W. 154°50' \V. 154° 50' W. 154°50' W. 154° 50' W. 15r24' W. 154°50' W. 154°50' W. 150°00' W. 151°24' W. 154°50' W. 150°12' W. 154°60' W. 150°I3' W. 154°50' W. 154° 50' W. 153°12' W. 154° 50' W. 150°06' W. 150°13' W. 150°13' W. 155°24' W. 157°30' \V. 155°24' W. 155°24' W. 156°24' W. 157°36' W. 155°24' W. 156°20' W. 156°20' W. 165°24' W. 156°20' W. 156°24' W. 156°20' W. 156°20' W. 156°20' W. 156°24' W. 156°20' W. 156°24' W. 157°30' W. 156°20' W. 157°36' \V. 167°36' W. 157°36' W. 157°36' W. 157°36' W. 120°32' W. 120°14' W. 120°25' W. 152°26' W. 152°05' W. 152°26' W. 151°19' W. 152°26' W. 151°19' W. 152°26' W. 152°20' W. 157°04' W. 162°26' W. I62°26' W. I62°26' W. 162°26' W. 120°21' \V. 120°21' \V. 120°21' \V. 120°21' W. !20°2r W. 130°17' W. 130° 17' W. 151°26' W. 151°26' W. 151 °5r W. 162°05' W. 1B3°05' W. 163°54' \V. 164°23' W. Ifi2°2f)' W. 164°23' W. 1.59°20' W. 158°53' W. 160°21' W. 157°20' W. 159°57' W. 159°57' W. 158°53' W. 160°20' W. 160'20' W. 160°2r W. In In In In In In In In In In In In In In In In In In In In Im M M M M M M In In In In In In In In In In In In In In In In In Im Im R In Im M M M In In In In In M Im Im Im Im M In In In Im M Im In In In M M M M M In In In In In In In In Im Im Im Cm. 142 141 141 140 140 140 139 139 139 138 137 136 134 133 131 131 129 128 127 122 117 144 143 138 137 133 113 144 144 144 142 141 140 136 136 136 136 135 133 124 115 114 109 93 104 96 147 133 159 143 135 127 149 140 137 135 133 143 99 95 95 88 138 139 127 123 153 132 150 ' 145 142 135 146 134 133 133 129 143 143 140 139 136 134 132 122 143 141 138 Nov.20.1950 . Nov. 23, 1950 Nov. 21, 1950 Do.. Nov. 23, 1950... Nov. 16, 1950 2°55' N. 5°04' N. 3°52' N. 3°52' N. 5°04' N. 3°62' N. 3°52' .N. 3°52' N. 6°13' N. 5°53' N. 3°52' N. 4°42' N. 6°13' N. 4°42'N. 6°25' N. 5°53' N. 4°42' N. 4>'42' N. 3"'54' N. 4°42' N. 4''42' N. 6°53' N. 4°42' N. 4°42' X. 4°42' N. 4°42' N. 3°52' N. 4°42' N. 5°53' N. 4°42' N. 5°53' N. 4°42' N. 5»63' N. 4°42' N. 4°42' N. 6°25' N. 6°25' N. 4°42' N. 6°25' N. 5°53' N. 4°42' N. 4°42' N. 4°42' N. 5°53' N. 6°25' N. 5°63' N. 6°25' N. 3°3fi' S. 6°25' N. 1°00' S. 0°04' N. 2°24' N. 5°00' S. 4°14' N. 4°14' N. 4°14' N. 4°14' N. 2°27' N. 3°31' N. 1°59' N. 1°28' S. 1°28' S. 2°14' N. 3°02' S. 1°22' N. 3''31' N. 2°27' N. 2°27' N. 2°27' .v. 4°33' S. 3°02' S. 1°69' N. 2°14' N. 1°59' N. 1°.59' N. 2°I4' N. 2°14' N. 2°14' N. 3°02' S. 2°01' N. 1°28' S. 1°59' N. 2°fll' N. 3°3r N. 3°31' X. 1°28' S. 1°28' S. 3°31' N. 160°20' \V. 159°03' W. 159°57' W. 1.59°57' W. 159°03' W. 1,59°20' W. 1.59°20' \V. l.';9°20' W. 158° 53' \V. 162°05' W. 169°20' W. 160°24' W. 158°53' W. 160°24' \V. 162°26' W. 162°05' W. 160°24' \V. 160°24' W. 159°26' W. 160°24' W. 160°24' \V. 162°05' W. 160°24' W. 160°24' W. 160°24' W. 160' 24' W. 159°20' W. 160°24' W. 162°05' W. 160°24' W. 162°05' W. 160°24' W. 162°05' \V. 160°24' W. 160°24' W. 162°26' W. 162°26' \V. 160°24' W. I62°26' \V. 162°05' W. 160°24' W. 160°24' \V. 160°24' W. 162°05' W. 162°26' W. 162°05' W. 162°26' W. 170°02' W. 167°32' W. 169°27' W. 168°48' VV. 168°44' VV. 170°08' VV. 154°60' VV. 1.54°56' VV. 1,54°56' W. 1.54°.%' VV. 15.5°26' VV. 1!J5°23' VV. 156°09' \V. 155°25' VV. 15.5°25' VV. 1.57°08' VV. I!i5°12'VV. 1.5.5°18'VV. 15.5°23'VV. 155°26' VV. 1.5.5°2fi' VV. 155°2fi' \V. 155°08' VV. 1.5,5° 12' VV. 156°09' VV. 157°08' VV. 156°09' VV. 1.56°09' VV. 1.57°08' W. 157°08' VV. 1.57°08' VV. 15.5°12' VV. 1.58° 15' VV. 155°25' VV. 156°09' VV. 158°15' W. 15,5°23' W. 155°23' VV. !55°25' VV. 156°25' VV. 155 23' VV. Im Im Im Im Im Im Im Im Ira Im Im Im Im Im Im Im Im Im Im Im Im Im Im Im Im Im Im Im Im Im Im Im Im Im Im Im Im Im Im Im Im Im Im Im Im Im Im R M M M In In In Im Im Im In In In In In In In In In In In In In In In In In In In In In In In Im Im Im Im Im Im Im Im Cm. 137 Sept. 17. 1951 - Do .. 137 136 Do Do - 135 135 Sept. 19,1951 Sept. 17, 1951... Do 130 Do... Do 130 122 Sept. 20, 1951 Sept. 19, 1951... Sent 17 1951 Nov. 24. 1950 122 Nov. 6, 1950 120 Nov. 16, 1950 120 Nov. 23, 1950-- 120 Spnt 17 1951 Nov. 24, 1950 118 Sept. 25. 1951 --. Sept. 17. 1951 - Do Nov. 23, 1950... 114 Nov 3, 1950 110 Nov. 28, 1950 - 110 Nov. 23, 1950.-- - 107 Nov. 2. 1950 105 Sept. 2. 1951 Nov. 16, 1950 Nov. 24, 1950.- --- 104 103 Do Nov. 2, 19iO 102 Sept. 12.1951 Sept. 15, 1951..- Sept. 12, 1951 Do Nov. 6. 1950 Nov 22, 1950 101 101 Do 99 .Nov. 23, 1960 .Vov. 24, 1950 ■. 99 98 Sept. 14, 1951 Sept. 12, 1951.- Sent 13 1951 Nov. 17. 1950 Nov. 23. 1950 96 94 Nov 27. 1950 93 Do Nov. 23. 1950 Nov. 27. 1950.- -. Nov 24. 1950 92 Sept. 12.1951 Sent 13 1951 88 87 Sept. 16. 1951 Sept 13, 1951 Nov. 28. 1950 86 Nov. 23. 1950 Nov. 24. 1950 Nov. 4, 1950 85 Do 85 Do -- - 83 Sept lli. 1951 Nov. 3. 19->0 Nov. 22. 1950 82 81 Sept 12, 1951 Nov. 2. 1950 Nov 4, 1950 78 Sept 15 1951 77 Nov. 22. 1950 77 Sept 14, 1951 Nov. 24. 1950 76 Do Do 71 Do Nov. 28. 1950 68 Do Nov. 4, 1950 63 Do Nov 27, 1950 . . 63 Oct 19, 1952 Nov. 30, 1950 61 Oct. 30, 1952 - Nov. 20, 1952 Nov. 11. 1950 Nov. 23, 1952 142 Oct. 31, 1952 153 135 Oct 29 1952 Nov 24 1952 .. . 132 Oct 27, 1952 Nov. 26, 1952 139 Oct 30, 1952 Nov. 19, 1952- - 131 Oct 27 1952 Dec. 12, 1953 - 126 Oct 30, 1952 Do 114 Oct. 27, 1952 Do 114 Oct 2H, 1952 Do 103 Oct 25 1950 Dec 6 1953 14$ Oct 31 1950 Dec 11, 1953 -.. 147 Dec. 7, 1953 146 Do Dec 3, 1953 144 Do Do 142 Nov. 1, 1952 Dec. 8, 19.53... 140 Do Dec 2. 1953 138 Do Dec. 5. 1953 137 Do Dec 11 1953 137 Do Dec 6, 1953 136 Nov. fi, 1952 Do 134 Do Do 127 Nov. 3, ig.w Dec 1. 1953 123 Do . - Dec. 2. 1953 122 Nov. 2, 19.52 Dec 7, 1953 . . 118 Nov. fi, 19.50 Dec. 8, 1053 110 Nov. 7, 1950 Dec. 7. 1953 107 Nov. 8, 19.50 Do . 105 Nov. 9, 1950 Dec. 8, 1953 105 Nov. 3(1. 19.50 Do 103 Nov. 9. 19.50 Do 103 Nov. Ifi. 19,50- Dec. 2, 1953 88 Nov. 24. 19.50 Dec. 9. 1953 87 Nov. 19. 1950.. Dec. 3, 1953 144 Nov. 1. ig-V) Dec 7, 1953 144 Nov. 21, 1950 Dec. 9, 1953 144 Do Dec. 11, 1953 144 Nov. 24. 1950 Do . . 144 Nov. 20. 1950 Dec. 3, 1953 Do 142 Do 141 Nov. 19.1950 Dec. 11, 1953 141 ' From length-weight relation. 256 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE Table 1. — Data on 740 yellowjin tuna specimens from the central equatorial Pacific for which maturity determinations were made in the laboratory — Continued Date Position Stage of maturity Fish length Date Position Stage of maturity Fish Latitude Longitude Latitude Longitude length Dec. 7, 1953 1°59' N. 3°31' N. 3°31' N. 1°69' N. 3°31' N. 4°33' S. 1°22' N. 3°02' S. 1=59' N. 3002' S. 2=27' N. 2°27' N. 3°02' S. l°S,9' N. 2°14' N. 156°09' W. 165°23' W. 155''23' W. 156°09' W. 155023' W. 165°08' W. 165°18' W. 155°12' W. 156°09' W. 155''12' \V. 155°26' W, 155°26' W. 155°12' W. 156°09' W. 157''08' W. Im Im Im Im Im Im Im Im Im Im Im Im Im Im Im Cm. 138 138 137 136 129 125 123 121 120 119 119 116 115 110 no Dec. 8, 1953... 2°H' N. 2°14' N. 2=14' N. 2°14' .N. 2''01' N. 2°14' N. 2=14' N. 2°14' N. 2°14' N. 2°14' N. 2°14' N. 2°14' N. 2°14' N. 2°01' N. 2'>14' N. l.=i7'08' W. 167°08' W. 1.57'08' W. 1.57°08' W. 158°15' W. 157°08' W. 157°08' W. 157°08' W. 157°08' W. 157°08' W. 157'>08' W. 157°08' W. 157°0S' W. 158°16' W. 157°08' W. Im Im Im Im Im Im Im Im Im Im Im Im Im Im Im Cm. Dec. 11, 1953._ Do. Do Dec. 7, 1963 Do Do Dec. 9, 1963 Dee. 8, 1953 Do.... Do Do Do.... Do Do 104 103 103 102 99 98 98 98 97 97 Dec. 11, 1953.. Dec. 1,1953 --. Dec. 5, 1953 Dec. 2, 1953 Dec. 7, 1953. - Dec. 2, 1953. _ Dec. 6, 1953 Do. Dec. 2, 1953 Do Dec. 9, 1963 Dec. 8, 1953 Dec. 7, 1953 Dec. 8, 1953 94 88 On several cruises, observations were made on the state of maturity of ovaries which, with a few exceptions, were then discarded. Although these field observations were subjective and liable to differences between observers, they were used to supplement the seasonal and areal coverage. After discussion with the various observers, and after comparisons of field observations with labor- atory classifications, we were able to classify most of the ovaries reliably into two groups, "inactive" (immature and intermediate) and "active" (ma- turing and ripe). Field classifications are given in table 2. Questionable observations were not considered, and are not included in the table. Table 2. — Data on yellowfin tuna specimens from the central equatorial Pacific for which maturity determinations were made in the fi,eld [A, active; I, inactive] Date Position Stage of maturity Fish length Date Position Stage of maturity Fish Latitude Longitude Latitude Longitude length May 28, 1954 May 30, 1954 4°02' N. 3°68' N. 4°02' N. 4°02' N. 5058' N. 4°17' N. 4'>02' N. 4''02' N. 4°02' N. 4°02' N. 4''02' N. 3°68' N. 4°45' N. 4°02' N . 4°02' N. 4°02' N. 4°17' N. 3°58' N. 4°45' N. 3°68' N. 3°68' N. 3°58' N. 3°58' N. 3°58' N. 3<=58' N. 3°58' N. 3°68' N. 3°68' N. 3'>58' N. S^SS' N. 4<'45' N. 3°58' N. 3°58' N. 3°58' N. 3°68' N. 4°46' N. 3'>58' N. 0°30' S. 0°13' S. 0°30' S. O'H' S. 169°34' W. 159°04' W. 159''34' W. 169°34' W. 162''52' W. 160''28' W. 159°34' W. 159°34' W. I59''34' W. 169°34' W. 159°34' W. 159°04' W. 160°11' W. l.W°34' W. IIJ9°34' W. 159°34' W. 160°28' W. 169''04' W. IfWIl' W. 159°04' W. 159°04' W. 159°04' W. 159''04' W. 159°04' W. 159°04' W. 159°04' W. 169°04' W. 169°04' W. 159''04' W. 159°04' W, 160°11' W. 169°04' W, 159°04' W. 159°04' W. 169°04' W. im'W W. 1.59°04' W. 160°19' W. 16O°02' W. 160°19' \V. 160°00' W. A A A A A A A I A A A A Cm. 149 140 139 123 120 118 114 118 Ufi 114 109 108 106 106 103 102 101 100 98 97 96 93 93 93 92 92 91 91 91 89 88 88 88 87 86 84 83 151 150 160 147 Junell,19M June 14, 1964 0°26' S. 0°13' S. O^SO' S. l''43'N. 1°52' N. 0°30' S. 0°30' S. 0026' S. 0°13' S. 0°60' N. Q°30' S. 0°30' S. 0°18' S. 0°13' S. CM' S. 0°18' S. 0°13' S. 0°14' S. 0°18' S. 0''50' N. 0°13' S. 0°14' S. 0°14' S. O'W S. 0°14' S. 0°14' S. Q°14' S. 2''01' N, 0°30' S. 2°01' N. 0°14' S. 0°14' S. 0°14' S. 0°18' S. 2°01' N. 0">14' S. 2-03' N. 0°18' S. 2°03' N. 2''03' N. 2''01' N. 158-67' W. 160°02' W. 160°19' W. 168°28' W. 156'>47' W. 160=19' W. 160°19' W. 168°57' W. Ifi0°02' W. 1.68°63' W. 160°19' W. 160°19' W. 160°16' W. Ifi0°02' W. lOO'OO' W. 160°16' W. 160°02' W. lecoo' w. 160°16' W. 168°53' W. 160'>02' W. leo-oo' w. IfiO'OO' w. 160°00' W. leo'oo' w. 160°00' W. 160°00' W. 167°09' W. 160'>19' \V. 1.57°09' W. 160°00' W. 160°00' W. 160°00' W. ll>0°16' W. 1,67<'09' W. lOO-OC W. 157°40' W. 160''lfi' W. 1.67°40' W. 1.57''40'W. 167°09' W. A A A A A A A A A A A A A A A A A A A A A A A A A A A A A I I I I I I I I I I I I Cm. 146 146 May 28,1954 June 16, 1964 146 Do June 3, 1954 144 May 17, 1954 May 27, 1954 June 7, 1954 June 15, 1954 143 143 Mav28, 1954 Do 143 Do Do ... June 11, 1964 June 14, 1954 142 142 Do Juno 10, 1964 June 15, 1964 141 Do 140 May 30, 1954 ... Do 140 May 25, 1954 June 13, 1964 139 Mav 28, 1954 June 14, 1954 137 Do... June 12, 1954 135 Do June 13, 1954 134 May 27,1954.. May 30, 1954 June 14, 1954 June 12, 1964 133 132 May 25, 1954 June 13, 1964 132 May 30, 1954 June 10, 1954 128 Do June 14, 1954 127 Do.... June 12, 1954 126 Do Do 125 Do Do 122 Do Do . 120 Do Do 120 Do.... Do June 8, 1964 120 Do 117 Do June 15, 1954 92 Do June 8, 1954 .- June 12, 1964 Do.. - 122 Mav 25, 1954 122 Mav 30, 1954 121 Do - . Do June 13, 1964 119 Do.. 118 Do Junes, 1964 June 12, 1964 116 Mav 25, 1954 116 May 30, 1964... June 4, 1954 June 13, 1954 June 4, 1954 116 .June 15, 1954 June 14, 1954 108 104 June 16, 1954 Do . Junes, 1954 102 June 12, 1954 94 SPAWNING OF YELLOWFIN TUNA 257 Table 2. — Data on yeltovifin tuna specimens from the central equatorial Pacific for which maturity determinations were made in Ike field — Continued Date Position Stage o( maturity Fish length Date Position Stage of maturity FUh Latitude Longitude Latitude Longitude length Auff 25 1952 3°26' X. l'>33' X. l'>33' N. 1°33' X. 1°33' X. 1''33' X. 3°26' X. 2''23' X. 2°23' X. 1°33' X. 1°00' X. 3°26' X. l'>33' X. 1°33' X. roo' X. 2-23' X. 1''33' X. l'>33' X. l-SS' X. 1''33' X. 2'>23' X. 4°28' X. 1°00' X. 4°28' X. 9°00' X. 6°10' X. 7°60' X. 7°50' X. 1°U'X. 2°08' N. 9°00' X. 2°08' X. 2°08' X. 4°43' X. 2°08' X. 4°43' X. 4°43' X. 3°22' X. 3''22' X. 3°22' X. 140''08' W. 140''13' W. 140°13' W. 140°13' W. 140°13' W. 140°13' W. 14O°08' W. 140°12' W. 140°12' W. 140°13' W. 140°22' W. 140°0S' W. 140°13' W. 140°13' W. 140°22' W. 140'>12' W. IWU' W. 140''13' W. 140°13' W. 140°13' W. I40°12' W. 139°51' W. 140°22' W. 139°51' W. 159°40' W. 160°02' W. 159°24' W. 159''24' W. 160°08' W. 160°24' W. 159''40' W. 160"'24' W. 160°24' W. 160°00' W. 160°24' W. 160°00' W. 160°00' W. 160°24' W. 160°24' W. 160°24' W. A I A A A A A A A A A On. 142 154 152 150 150 149 148 148 148 148 148 147 147 144 144 142 142 141 141 138 132 131 121 112 147 141 140 140 134 128 128 123 107 140 125 112 111 108 104 100 Aug. 24, 1953 4°43' X. 4°43' X. 4°43' X. 4°43' X. 4°43' X. 4'>43' X. 1°42' X. 4°04' X. r42' N. 2''.33' X. 3005' X. 3°05' X. 2°25' X. 3°05' X. 1°42' X. 2''33' X. .3''31' X. 1°42' X. 2°25' X. 2°57' X. 3°39' X. 2°28' X. 3°39' X. 3°49' X. 2005' X. 3°49' X. 3»39' X. 2»28' X. 3°26' X. 2°28' X. 2°57' X. 1°48' X. 2°08' X. 2°57' X. 2''05' X. 1°48' X. 2'>08' X. 2°05' X. 1°22' X. 2°28' N. leo'oo' W. 16O°0O' W. 160"'00' W. 160°00' W. 160°00' W. 160'>00' \V. 141=24' W. 140°09' \V. 141024' W. 143<'22' W. 14O°02' W. 140°02' W. 140-32' \V. I40''02' W. 141°24' W. 143°22' \V. 140°2)t' W. 141''24' W. I40''32' W. 147°22' W. 151°,54' W. 150''38' W. 151-54' W. 152-10' W. 150-23' W. 152-10' W. 151-54' W. 150-38' W. 151-40' \V. 150-38' W. 147-22' W. 150-05' W. 145-21' W. 147-22' W. 150-23' W. 150-05' W. 145-21' W. 150-23' W. 149-54' W. 150"3S' W. A A A A A Cm. 99 Aug. 27, 1952 Do Do Do 96 Do... Do 9fl 95 Do Do 93 Do Do... .Sept. 7, 1952 Sept. 3, 1952 Sept. 7, 1952 Sept. 9, 1952 .Sept. 2, 1952 Do 88 Aug. 25, 1952 156 Aug. 26, 1952 Do 150 149 Aug. 27, 1952 - Aug. 28, 1952 148 147 Aug 25 1952 145 Aug 27, 1952 Sept. 5. 1952 145 Do Sept. 2, 1952 Sept. 7, 1952 144 Aug. 28, 1952 Aug. 26, 1952 143 Sept. 9, 1952 Sept. I, 1952 143 Aug 27 1952 142 Do Sept. 7, 1952 Sept. 5,1962 Sent. 11. 1952 Sept. 18, 1952 Sept. 16, 1952.... Sept. 18, 1952... Sept. 19, 1952 139 Do 136 Do 157 Aug. 26, 1952 1.50 Aug. 24, 19.52 Aug. 28, 1952. Aug. 24, 1952 Aug 27 1953 146 144 143 Sept. 15, 1952 142 .Aug. 25, 1953 Aug. 26,1953 Do Aug. 21, 1953 Sept. 19, 1952 Sept. 18, 1952 142 138 Sept. 16, 1952 Sept. 17, 1952 Sept. 16, 19.52 137 137 Aug. 22. 1953 Aug. 27, 19.53 Aug. 22, 1953.. Do 135 Sept. 11, 1952.... 148 Sept. 14, 19.52- Sept. 10, 1952 144 143 Aug. 24, ig.w .\ug. 22, 1953 Sept. 11, 1952 ... . 143 Sept. 15, 1952 142 Sept. 14, 1952 135 Do Sept. 10, 1952 134 AuE 23 1953 Sept. 15, 1952 134 Do Sept. 13, 1952 133 Do Sept. 16, 1952 117 Additional data (table 3) are available from field observations reported by the Iwate Prefecture Fishery Experiment Station (1953a and 1953b), which were obtained from Japanese longline expeditions into this area. As with the POFI field observations, the stages of maturity were combined into two groups, "active" and "in- active", and the "spent" category was disregarded. Other pertinent information found in these reports is as follows: Tlie fishing area for the April cruise was between latitudes 9° N. and 11° N. and longitudes 170° W. and 173° W. Fish caught on this cruise ranged from 110 to 150 cm. in length, with only one fish measuring less than 120 cm. Fishing during June and July was done at 3° N. to 4° X. and 175° W. to 177° W. Fork lengths ranged fi'om 114 to 173 cm., with only two fish measuring less than 120 cm. Eighty percent of the fish were caught in June, and the rest were caught in July. Table 3. — A^umber of yellowfin tuna in various stages of maturity, according to Iwate Prefecture Fishery Experiment Station Date 3m S £ 03 a TO Location Longitude Latitude Apr. 4-24, 1953... June 22-July 3, 1953. 3 29 4 41 10 97 14 26 4 22 9°N.-11°X... 3-X.-4-X.... 170° W.-173° W. 175° W.-177- W. Note.— For further data see station reports (1953a and 1953b). SIZE OF FISH AT FIRST SPAWNING To determine the size of first-spawTiing fish, the fork lengths collected by POFI were grouped into classes of 10 cm., and the percentage of fish in the "active" category (maturing and ripe stages), as determined by ovary examination, was calculated for each lengtli class. The results, illustrated in figure 1 , show t hat all the fish smaller than 70 cm. were in a nonspawning condition. In the 70-to-79-cm. class (about 15 to 22 lbs.), 6.9 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 60 70 80 90 100 110 120 130 140 150 69 79 89 99 109 119 129 LENGTH (CM) 139 149 159 12 18 26 37 50 65 84 106 131 160 APPROX. WEIGHT(LBS) Figure 1. — Percentages of sexually active fish at different fork lengths. Figures in parentheses indicate the num- bers of individuals on which the percentages are based. percent were in the maturing or ripe stages. The percentage of sexually active fish increased gradu- ally and irregularly from this length class through the llO-to-119-cm. class (about 57 to 72 lbs.), of which 17.4 percent were active. In the next 10-cm. class (about 74 to 92 lbs.), the percentage of reproductively active fish jumped sharply to 47.0 percent. Above this class the percentage of active fish increased steadily with length. Of the fish measuring 150 to 159 cm. (about 145 to 172 lbs.), 66.7 percent were active. These data suggest that, although yellowfin as small as 70 cm. are capable of reproducing, the greater part of the population reaches sexual maturity at about 120 cm. Schaefer and Marr (1948), however, noted that in Costa Rican waters yellowfin ranging from 70 to 100 cm. spawn later in the year than the larger fish. This presents the possibility that larger fish have longer spawn- ing periods than smaller fish, which in turn sug- gests that the smaller percentage of sexually active fish from 70 to 120 cm. in our samples may have resulted from a shorter spawning season rather than from a diff'erence between the propor- tions of sexually mature fish above 120 cm. and those below 120 cm. Although the representation of fish from 70 to 120 cm. for each month is spotty in our samples, an examination of the monthly percent maturing and ripe (table 4) shows the peak percentage to be far less than that reached by the larger fish. This supports our interpre- tation of the results, that is, that the greater part of the population reaches sexual maturity at about 120 cm. Table 4. — Monthly percentages of sexually active yellowfin tuna below 120 cm. fork length Month Fraction active Percent active January 1/12 2/26 0/1 2/18 11/101 11/45 0/1 3/24 4/12 0/4 0/31 0/33 8.3 7.6 0.0 April .. 11.0 10.0 June 24.4 July 0.0 12.5 September .. ... 33.3 0.0 November 0.0 0.0 LOCALITY OF SPAWNING The data were grouped by months and by 10-degree longitudinal sections. The data for those ovaries collected between 115°00' W. and 124°59' W. are shown in table 5 in the 120° W. longitudinal section (the midpoint of that section), those collected between 125°00' and i;34°59' W. in the 130° W. section, and so on, with the excep- tion of the 180° section, which includes 175°00' W. to 180°. Because the percentage of sexually active fish below 120 cm. was so much smaller, only fish above this size were considered in order to get results that could be used for comparison. The percentage of active fish for each month for each 10-degree section was calculated. The percent- ages for June and July along 180° were calculated from summarized Japanese data, which did not separate the catch of those 2 months. To arrive at the monthly totals for these months (in the extreme right-hand column of table 5), the 193 fish caught along 180° were separated into 154 fish for June and 39 fish for July, because 80 per- cent of the catch was made in June. The results (table 5) show that all the sections had at least one month in which 85 percent or more of the fish were sexuallv active. This, coupled SPAWNING OF YELLOWFIN TUNA 259 Table 5. — Fractions of samples of seitialty active yetlowfin tuna (maturing and ripe) at various longitudes, by , IPcrcontage of se.vually mature fish in sample in parentheses) lonlhs Month At longitude- Total ISO" 170° W. 160° W. 150° W. 140° W. 130° W. 120° W. I (16.7%) |(40.6%, 1 (16.7%) 11(49.3%) ^ (81.8%) I (50.0%) ^^(46.7%) March II (87.5%) 1 (100.0%) |(97.1%) ^|(94.2%) \i)ril =2 (90.3%) If (90.3%) Mav 1 (87.5%) § (85.2%) ■| (100.0%) |(87.2%) li '^•''^''' 1 (77.8%) 1 (88.4%) ^ (90.0%) 1 (100.0%) ^(85.7%) |(85.0%) 1 (66.7%) ^ (83.3%) Au ust § (69.8%) 1 (100.0%) 1(28.2%) i <*'■*''<'> ^ fg(27.8%) ^(72.2%) |r73.3%) J|(67.5%) j (100.0%) 1 (37.5%) 1 (33.3%) ^ (41.7%) I (66.7%? 1; (17.9%) 1 (0.0%) \ (50.0%) \ (20.0%) 5 (25.0%) li (0.0%) ■Y (0.0%) ^2(0.0%) with tlie fact that larvae below 10 mm. have been found in all of these sections (Matsumoto') indicates that yellowfin spawning occurs through- out the central equatorial Pacific. The fact that spawning probably occurs throughout the entire equatorial Pacific is indicated by additional records of spawning yellowfin in the western area by Wade (1950 and 1951), Marr (1948), and Shimada (1951), and in the eastern area by Schaefer and Marr (1948) and Mead (1951). TIME OF SPAWNING The percentage of sexually active fish of 120 cm. and longer was calculated for each month of the year and was plotted on a graph (fig. 2). Yellow- fin that had almost reached the spawning state were found in each month except December, and the greatest percentages of active fish occurred from March (94.2%) through July (83.3%). It was only during November, December, and January that the occurrence of maturing and ripe fish dropped below 40 percent. This, however, does not prove that spawning is a year-round activity, inasmuch as the length of time that the I .Miit.suniuto. Walter M.: T">escriptions of four species of tuna larvae and their distribution in central Pacific waters. POFI. (Unpublished MS.) . . cry. 1/11 IV Ar-TiurlBASED ON OBSERVATIONS FROM • •btxuALLT "l-l l''tj-^^|_ SOURCES ^ < EARLY STAGE OF RESORPTION"! BASED ON OVARIES ^ COLLECTED AFTER . -• LATE STAGE OF RESORPTION J 1951 ONLY 80 - 1 1 T" 1 i 1 — 1 1 1 1 1 1 60 - / ^ \ / / 40 < / / A / _ 20 n - / >/ V 1 A- _L \ 1 1 T" ^ • jI: '*- \ JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC Figure 2.— Monthly percentages of yellowfin tuna -■^exnally active or with rcsitUial eggs. fish are in these stages before spawning is not known. To define tiie spawning season further, the occurrence of residual eggs in these larger fish was invc^stigated with respect to time. Tlie results, plotted in figure 2, show that ovaries with early- 260 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE stage residual eggs have the same occurrence pattern as maturing and ripe ovaries. This is true for all the months except January, which is represented by an inadequate sample. The occur- rence of these early-stage residual eggs indicates that spawning actually is a year-round occurrence. Spawning in other equatorial areas of the Pacific likewise seems to be protracted. Schaefer and Marr (1948) found indications of a prolonged spawning season off Costa Rica. Wade (1950) found that the spawning period of yellowfin in the Philippine Islands extended over a considerable period, but that it was most intense during May, June, July, and August. It is probable that the of these stages are based on gross microscopic examination and are intended to aid future workers in recognizing these structures. Immediately after spawning, these residual eggs (fig. 3) generally resemble the ripe eggs, except that they become shrivelled owing to shrinking of the yolk mass and the resulting collapse of the chorion. The oil sac is usually ruptured, and the released oil appears as bright yellow droplets. The eggs at this stage are still loose and translucent. Subsequently the eggs lose their translucence and collect in masses of semiopaque tubules. The eggs are not within the tubule but are entangled in the manv disordered convolutions of the tubule. Figure 3. — Individual residual eggs; O., oil droplet; O. S., oil sac. prolonged spawning season is accompanied by multiple spawning — in other words, there is more than one spawning per fish in a spawning season. June (1953) considered this to be true for yellowfin in Hawaiian waters, after studying the progression of modal groups in egg-diameter frequencies. DESCRIPTION OF STAGES IN RESORP- TION OF RESIDUAL EGGS In the beginning of this study, several structures found in the ovaries could not be readily identified. As more ovaries were examined, it became evident that these structures were the remains of ripe eggs from a previous spawning which were in different stages of resorption. The following descriptions / .-^-^ ^ ^**^^^« k>-v { 11 ^^ o.t. i.t. IMM 1 1 F.IGURE 4. — Piece of tubule teased from ovary with residual eggs; i. t., inner tubule; o. t., outer tubule. SPAWNING OF YELLOWFIN TUNA 261 The tubular diameter is about 0.20 mm. Within this tubuh' lies anotiier tubule with a diameter of 0.0.5 mm. Circular transverse ridges on the wall of the outer tubule give it a striated appearance. Figure 4 shows a short section of a tubule that had been teased from a mass. Histologically, these masses of tubules and eggs are found to be surrounded by a connective tissue stroma (fig. 5). The wall of the outer tubule seems to be composed of reticular connective tissue. The wall of tlie inner tubule is made up of a single layer of closely arranged minute cells (3 M diameter) with relatively large, deep-staining nuclei. The origin and function of these tubules are open to question, but their pro.ximity to the residual eggs suggests that they are involved in the absorption of these eggs. [^DEVELOPING PORTION ^^DEGENERATING PORTION Figure 5. — Above: Part of section through ovary showing residual egg mass in xilir. c, connective tissue capsule; d. e., developing egg; i. I., inner tubule; o. t., outer tubule; r. e., residual egg. Below: Diagram of this section, outlining developing and degenerating portions. 262 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE The masses of eggs, tubules, and connective tissue which are scattered throughout the ovary appear to shrink with the passage of time. An examination of later stages shows that the residual eggs are not arranged entirely haphazardly but are lined up to form indistinct cords (fig. 6). These masses eventually shrink to nondescript particles (fig. 7) before they are finally lost in the ovarv. OCCURRENCE OF NEMATODES IN THE OVARIES While examining the eggs, we observed several ovaries with nematodes, ranging from 0.5 cm. to 4 cm. in length. The specimens were in too poor a state of preservation to identify. Of 25 ovaries examined for nematodes, 22 (88%) were infested. The extent of infestation did not appear to be serious enough to affect the Figure 6. — Above: Residual egg mass teased from ovary. Below: Diagram of this mass, outlining the rows of eggs. SPAWNING OF YELLOWFIN TtJNA 263 Figure 7. — Part of ovary showing shrunken masses of residual eggs; m., mass of residual eggs. functioning of the ovaries. There were seldom more than five worms in a single ovary, and in only one instance did the ovarian tissue seem to be pathological owing to heavy infestation. Fish with infested ovaries were found throughout the central equatorial Pacific. SUMMARY This study is based on data obtained in the field relative to the time and place of spawning and the size of yollowfin tuna at time of spawning, and on laboratory examination of ovaries of yellow- fin tuna obtained on POFI e.xploratorv-fishing trips made in the central equatorial Pacific from February 1950 to June 1954. Study of the ovaries and of the data on tlie size and distribution of the spawning fish led to the following conclusions: (1) The size at sexual maturity may be as small as 70 cm., but usually is greater than 120 cm.; (2) the spawning season extends throughout most of the year, with November, December, and January the months of lowest spawning intensity; (3) the spawning grounds seem to include the entire equatorial Pacific. During the course of this investigation, stages in the resorption of residual eggs were observed and described. Unidentified nematodes were found in 88 per- cent of a sample of 25 ovaries. In most instances, the nematodes did not seem to be present in sufficient numbers to affect egg production seri- ously. LITERATURE CITED BiNi, Giorgio. 1952. Osservazioni suUa fauna marina delle coste del Chile e del Peril con sp<'ciak' riguardo alle specie ittiche in gcnerale ed ai tonni in particolare. BoUet- tino di Pesca, Piscicoltura e Idriobiologia, vol. 7 (n. s.), fasc. 1: 11-60. Roma. IwATE Prefecture Fishery Experiment St.^tio.v. 1953a. South Sea tuna fishing survey. Rept. No. 1. 1953b. South Sea tuna fishing survey. Rept. No. 2. June, Fred C. 1953. Spawning of yellowfin tuna in Hawaiian waters. U. S. Department of the Interior, Fish and Wildlife Service, Fishery Bull., No. 77, vol. 54, pp. 47-6-1. Marr, John C. 1948. Observations on the spawning of oceanic skipjack (Katsuwonus pelamis) and yellowfin tuna {Neothunnus macroptent.i) in the northern Marshall Islands. U. S. Department of the Interior, Fish and Wildlife Service, Fishery Bull., No. 44, vol. 51, pp. 201-206. Mead, Giles W. 1951. Postlarval \eothunnus mricropterux, Auxis (hazard, and Eiithynnus linealus from the Pacific Coast of Central America. U. S. Department of the Interior, Fish and WildUfe Service, Fishery Bull., No. 63, vol. 52, pp. 121-127. 264 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE ScHAEPER, MiLNER B., and J. C. Marr. 1948. Spawning of yellowfin tuna (Neothunnus macrop- terus) and skipjack (Katsuwonus pelamis) in the Pacific Ocean off Central America, with descriptions of juveniles. U. S. Department of the Interior, Fish and Wildlife Service, Fishery Bull., No. 44, vol. 51, pp. 187-196. Shimada, Bell M. 1951. Contributions to the biology of tunas from the western equatorial Pacific. U. S. Department of the Interior, Fish and Wildlife Service, Fishery Bull., No. 62, vol. 52, pp. 111-119. Wade, Charles B. 1950. Observations on the spawning of Philippine tuna. U. S. Department of the Interior, Fish and Wildlife Service, Fishery Bull., No. 55, vol. 51, pp. 409-423. 1951. Larvae of tuna and tuna-like fishes from Philippine waters. U. S. Department of the Interior, Fish and Wildlife Service, Fishery Bull., No. 57, vol. 51, pp. 445-485. U. S. GOVERNMENT PRINTING OFFICE : 1957 O -406090 A METHOD OF ESTIMATING ABUNDANCE OF GROUNDFISH ON GEORGES BANK By George a. Rounsefell, Fishery Research Biologist In studying the fluctuations in iitjundiinc.e of various species tliat comprise the catcli, it is of paramount importance to know how tlie abun- dance of each species usually vaiies from l)ank to bank and from depth to depth. When vessels arc fishing chiefly for a particular species, they seek the grounds and the depths at which that species is most easily taken in abundance. For such a species, the catch per unit of fishing effort will measure the relative abundance with considerable accuracy, since the vessels will shift to grounds and depths yielding the highest catches. For other species, however, the fluctuations in actual abundance cannot be measured without sufficient knowledge of their average relative density in different depths and on different grounds. There- fore, a study of the distribution of these other species by depth and fishing grounds is a necessary preliminary to a study of their annual fluctuations in abundance. Knowledge of the relative density of each species by fishing grounds is of considerable value from other standpoints. What effect is a fishery in any certain area likely to have on the stock of each species? In certain cases the question arises: What effect will a change in the size of the mesh of the trawl have on the catches? Only by knowing the density of each species by areas and depths can these questions be answered. For many species not extensively sought for economic reasons, it is desirable to know whether there is a possibility of the catch being increased, should it become desirable to increase production. There is also the problem whether the range of a species is wholly covered by the fishery or may extend to areas beyond. Tlic methods developed in this paper have been followed by the haddock investigation of the N'oi'th Atlantic Fishery Investigations in computing indexes of abundance from 1931 to 19.'):i. MATERIAL To obtain a measure of the relative density of each species it was necessary to ascertain the quantity caught by certain units of fishing effort. Collection of the data necessary for this study was started in the fall of 1931, at the Boston Fish Pier, and IS continuing. In 1942 this collection was extended to the ports of Gloucester and New- Bedford, Mass.; in 1953 it was extended to Provincetown, Mass., and Rockland and Portland, Maine. A full description of the methods of collection is given by Rounsefell (1948). The essential data collected for each vessel interviewed are as follows: 1. Name of the vessel, and type of gear employed. 2. Day and hour of departure and of arrival at port. 3. Positions fished, by "unit" areas, each unit comprising a rectangle of 10' of latitude and 10' of longitude, or about 10 miles by 7-plus miles. 4. Depth, in fathoms, at each fishing position. 5. E.'itimated amount of the catch, in thousands of pounds, at each fishing position. 6. Estimated proportion of each species taken on different fishing grounds. 7. For line-trawl vessels, the number of tubs of gear set out at each fishing location. 8. For otter-trawl vessels, an estimate of the time spent on each fishing ground. 9. For otter-trawl vessels, the total amoimt of time lost on the trip (other than the usual running time to and from the banks) because of such occurrences as torn nets, engine trouble, or stormy weather. CALCULATION OF CATCH PER FISHING DAY FOR OTTER-TRAWL VESSELS In order to obtain for otter-trawl vessels a measm-e of fishing effort more or less independent of weather, distance traveled . . ., it was found desirable to calculate the amount of time the vessel actually spent in fishing while on the fishing grounds. P'rom the data available, the actuid number of days the vessel was absent from port 265 266 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE was calculated to the nearest tenth of a day. The time spent away from port was consumed partly in the voyage to and from the bank. To discount this, the groups of otter-trawl vessels selected for study were questioned about their average speed under working conditions, and in many cases this was checked for various voyages by means of radio reports. Tables were made to show the time (to the nearest tenth of a day) that it would take a vessel to make the trip from port to each statistical subarea (see fig. 1.) at the average speed of the selected group. The time the vessel was absent from port, minus this running time, and also minus any time lost by bad weather, . . ., gave the calculated number of fishing days for each trip. On the average, these calculated fishing times were found to agree with the esti- mated fishing times obtained from the interviews but they were used instead of the estimated times given in the interviews because they wei-e con- sidered less subject to personal judgment. In the preceding calculations, the distance was measured from port to a point in the subarea empirically selected as being nearest to the avei'age position fished in that subarea (as shown by plots of many fishing positions over several years). Wlien the vessel fished in two subareas that extended in the same direction from port, only the voyage to and from the most distant of the two subareas was used. When more than one subarea was fished and the subareas were not in line, the running time was taken from port to one subarea, then between subareas, and finally from the last subarea back to port. When a vessel fished in more than one subarea, the calcu'ated fishing time was divided between the subareas in the same proportion as the esti- mated fishing time given in the interview, except that when the estimated and calculated times did not agree and the estimated time in a certain sub- area was only 1 day or a fraction of a day, this estimated time was considered correct, and adjust- ment was made in the time for the subarea or sub- areas in which more fishing was conducted. Al- though this approach is not easily susceptible of statistical proof, it is obvious that the estimates of the shorter periods of time are much more apt to be correct than those of the longer periods. A mate may easily be uncertain whether they fished 6 days or 7 days in a subarea, but an estimate of 12 hours is seldom far off. In some cases, the mate did not remember the number of hours spent in a subarea in which the vessel did little fishing but knew the number of tows made by the otter trawl. In these cases, each tow was considered as an estimated one-tenth of a fishing day. This estimate is predicated on the number of tows per day by large otter trawls, as indicated by careful notes and logs kept by several vessels for W. C. Herrington. These data showed that on the average there were 10 tows per day. SELECTION OF OTTER-TRAWL VESSELS FOR DETERMINING RELATIVE ABUNDANCE The first step in obtaining the catch per day was to select two groups of Boston otter trawlers, each group fairly homogeneous with respect to size of vessels. The first group of 12 large (over 150 gross tons) otter trawlers ranged in size from 163 to 173 gross tons, with an average of 167 gross tons. The second group of 13 vessels ranged from 229 to 262 gross tons, with an average of 247 gross tons, or 48 percent larger than the first group in average size. However, after the data on catch per day were tabulated, it was found that the selection of these groups on the basis of gross ton- nage was apparently erroneous. In order to de- cide on the proper basis for selection, all 25 boats were compared for the year 1938. The levels of fish abundance differ considerably between the New England and Nova Scotia banks; therefore the comparison of fishing ability was con- fined to the New England banks, which accounted for 57 percent of the season's catch. In making tliis comparison, it was found that some of these boats did considerable fishing for ocean perch, while others did little or none. As this is a specialized fishery that yields a far greater poundage per unit of fishing effort, it was necessary to eliminate this cause of variability in order to obtain a valid comparison. Tabulation of the 146 trips or portions of trips made in the deep waters (more than 60 fathoms) of Subareas XXII, F, G, and H in wliich ocean perch were taken, showed 72 instances in whicli over 80 percent of the catch consisted of ocean perch; these trips averaged 95 percent ocean perch. Another 29 trips had be- tween 41 and 80 percent ocean perch and averaged 58 percent, and 45 trips had from 1 to 40 percent ocean perch and averaged 16 percent. Obviously, on the trips vvitli a higli percentage of ocean perch KSTIMATING ABUNDANCE OF GROUNDFISH ON GEORGES BANK 267 ^ >, c3 *^ ■/. u *^ X, r^ » V *^ o "" - «s - Zi X ? X -^^•i = 55 S i S "5 =! '5 = o! 5 s 268 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE the vessels had spent all or a large portion of their time seeking this species. Therefore, all trips con- sisting of over 40 percent ocean perch were elim- inated from the comparison. This amounted to less than 10 percent of tlie catcli in Area XXII. The coefficient of correlation between the aver- age catch per day of the 25 vessels and their gross tonnages, -f-0.4033, was not statistically signifi- cant. What correlation exists is undoubtedly due to the linkage of gross tonnage to other factors, treated below. Since these vessels all employ the same type and size of otter trawl, regardless of differences in the sizes of the vessels, the absence of a significant correlation between size of vessel and fishing ability is not surprising. Obviously, more important factors are the amount of sea bottom covered by the net at each tow and the number of tows made each day. The amount of ground covered in a tow will depend largely on the speed and power of the vessel. Therefore, the catch per day was corre- lated with the power of the vessels. Instead of correlating catch per day directly with horsepower, the ratio of horsepower to length was used as the criterion of power, since the horsepower of a vessel depends more on length than on tonnage. Also, the use of horsepower directly, instead of the ratio, does not give a true estimate of towing ability. This correlation gave a statistically significant coefficient of correlation of +0.75. Since the newer vessels take advantage of all improvements in design and usually obtain tlie best crews, it was suspected that age of the vessel might play a part. The correlation of age of vessel and catch per day gave a significant coeffi- cient of —0.6643, showing that the newer vessels were superior. However, as the newer vessels were often better powered than the older vessels, it was necessary to eliminate the effect of the other variable in comparing the catch per day with either horse- power-length ratio or age of vessel. The coefficient of partial correlation of catch per day and horsepower-length ratio, with age of vessel fixed, was +0.686. The coefficient of par- tial correlation of catch per day and age of vessel, with horsepower-length ratio fixed, was —0.497. Squaring the two partial-correlation coefficients shows that 47 percent of the variability in catch per day was due to differences in the horsepower- length ratio of the vessels and an additional 25 percent of the variability was due to dift'erences in age of the vessels, leaving only 28 percent of the variability in catch per day unaccounted for. In obtaining a more accurate method of rating each boat according to its fishing ability, both age of vessel and horsepower-length ratio were taken into account. For each boat, the amount in standard deviations that it varied from the mean of the horsepower-length ratio was obtained. The same was done for age of vessel. The two figures were then combined, but the age ratio was weighted by 0.52, the ratio of its influence on the catch to the influence of power. The correlation of this adjusted rating of the individual boats with their catch per day of fishing gives a correlation coefficient of +0.817. Squar- ing the coefficient shows that the differences in the adjusted ratings of the vessels accounts for 67 percent of the variability in the catch per day. This accounts for all but 33 percent of the vari- ability in catcli per day, agreeing closely with the 28 percent shown by tlie two coefficients of partial correlation. Because such a large proportion of the varia- bility in catch per day is due to the age and power of the vessel, it was obviously incorrect to intro- duce new boats into the calculation. Therefore, it was decided to reject the data from all vessels except 16 that fished continuously from 1932 through 1938. The use of the same boats every year meant that variations due to age and power of vessel could be held to a minimum. Whether the correlation between age of vessel and catch per day was due to obsolescence or to the increased efficiency of the newer boats cannot be deduced from the correlation. It is safe to say, however, that at least a large share of it is due to improve- ments otlier than power in the design of the newer boats. ADJUSTMENT FOR CATCHING ABILITY OF TWO GROUPS OF OTTER TRAWLERS As a preliminary step in analyzing the catch per unit of fishing effort in various areas and at various seasons it was desirable to determine the relative catching ability of the two groups of otter trawlers. This was to make possible the pooling of their catches so that one final curve of abundance could be obtained for each area. ESTIMATING ABUNDANCE OF GROUNDFISH ON GEORGES BANK 269 The date for this comparison were ohteinc fistiing in each unit area really represent the average for the whole unit area and not for any particular point. Tlie metliod finally adopted was to construct frecjuency ])olygons of days of fishing across the entire Area XXII from north to south and from west to east for each column and each row of unit areas. These frequencies then were smoothed so tliat the amount under the curve would average the correct number of days of fish- ing in each unit area. After the fishing-intensity contoiu's luul i)een drawn (see fig. 4), the area of shallow, medium, and deep water within each contour was measured witli a planimeter. Multiplying the midpoint in tlie range of fishing intensity within contour lines by the areas enclosed gave a total of 82,479 fishing (hiys, compared witli 82,127 in tlie original data, an error of only sligiitly over 1 [)ercent.- B\' this 272 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE P3 3 O X O "T xn P ■g CT> t M O G S ^ (/J s^ S ^ _Q CO fa^ h h J +log J [.mj ul [.mJ + +log y = l There might be some question about the ad- visability of using an unweighted average instead of a weighted average in obtaining these geometric- mean ratios. At this point it must be remembered that in such a chronological series, weighting of the data (thus giving much more weight to certain years) may introduce a bias which we cannot measure. Using the logaritlims of the ratios, an imalvsis of variance was made, which showed no 276 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE significant difference between the means of the years; therefore the years were averaged without weighting. From the analysis of the variance of the loga- rithms of the ratios, the least significant mean difference {P=.05) between ratios was calculated for the mean ratios of the species in the shallow zone and in the deep zone (Snedecor 1940, p. 344) ; these are shown in table 2. Examination of table 2 reveals that the difference in availability is usually statistically significant for any two species at the same depth. The relative abundance (availability) at each depth is shown in figure 6. In interpreting this figure it must be borne in mind that the chief object of this otter-trawl fishery by large vessels has been haddock. Thus, the sample of data used in this table comprises a total of 5,437 cor- rected days of fishing with a catch of 92,201,000 pounds. Of this total, 43.4 percent, or 39,955,000 pounds was large haddock, and 29.2 percent, or 26,914,000 pounds was scrod haddock, making a total of 72.6 percent haddock. Since haddock was the principal object of this fishery, the fleet concentrated where haddock could be taken in greatest abundance. Thus, the fact that the fleet spent most of its time in water of medium depth would indicate that the haddock is most often found at that depth. When the haddock move into shallow water for a 100 - _ SHALLOW -| 50 1 -1 J » - 1 - - 1- z UJ 50 — 1 1 MEDIUM 1 1 (r J - H UJ o. - - DEEP 90 — ~ - - o < CD < _l OD O CO z o 2 O 3 m < X < Q* O U (E O o o a o < o o (E O Vi a o o o o o Q < uJ < O o o tu -I o o o o V) o < Ul < X o o o a o < X Figure 6. — Relative abundance of each species of groundflsh in each depth zone in Area XXII South, from otter-trawl catches. ESTIMATING ABUNDANCE OF GROUNDFISH ON GEORGES BANK Table 2. — Dialribution of species of groundfish according to depth zones on Georges Rank. 1932-38 277 Market site (iMunds) As ratio of medium depth As percent at each depth Species Siiallow zone Deep zone Shallow zone Medium sonc Deep lone Blackback 312.6 303.1 187.2 129.1 113.7 91.5 89.1 78.7 65.9 57.6 41.0 31.8 30.9 28.7 15.3 22.4 24.2 12 fi 54.3 ini.2 3.^0 54.0 88.3 58.9 389.9 671.4 93.8 261.2 148. fi 6.4 3,917.0 6.607.0 71.86 70.93 62.44 45.55 36.11 40.40 36.65 29.48 29.31 10. .W 5.05 14.10 7.88 10.35 12.57 22.99 23.40 33.36 35.29 31.76 44.15 41.14 37.45 44.48 18.26 12.31 44.33 25.50 36.06 82.17 2.49 1.49 5.15 5.66 Yellowtail . . 4.20 Halibut - 19.16 Haddock nareel Over2)4 32.14 Cod (market) - ni to 10 15. 45 Haddock (scrod) Under 2H 22.21 Wolffish 33.07 10 to 25 26.21 71.21 82 64 Cod (whale) Over 25 41.58 Hake 66.62 53.59 Cod (scrod) - - IMto2J4 5.26 97.51 Redfish (owan perth) 98.51 106.4 3.7 106.9 4.2 33.96 31.92 34.12 321.2 5.927 4.028.9 65,580 1,087.9 20.694 short time, tlic fleet follows them. Because we get catches from shallow water only for the period that the fleet is there (when haddock are abundant), it appears as thougli haddock are equally abundant in shallow and in medium-depth water, but such is not the case. According to figure 6, the smaller sizes of had- dock tend to be less abundant in deep water, but the true difference between the depth zones for this species may be more pronounced than the data indicate. In the case of pollock, the data are somewiiat misleading. The otter trawlers make a few large catches of pollock in deep water in the fall and winter months, when the pollock are concentrated in dense schools, but these fish are caught only incidentally to the pursuit of haddock during the remainder of the year. Thus, although the data indicate that the pollock is chiefly a deep-water species, pollock are known to frequent all depths. For example, along the Maine coast the pollock school at the surface and are captured by small purse-seine boats. SUMMARY 1. The fishing intensity, by areas and depths, by otter trawlers during a period of 10 years (1928 to 1937, except 1931) was determined for Georges Bank, Subareas XXII, G, H, J, M, \, and O. The information was obtained from i)lo(s of more than 32,000 days of fishing by otter trawlers of more tlian 50 gross tons. 2. During the 10-year period, the otter trawlers fished 23.4 percent of their time in water of to 30 fathoms in depth, 53.0 percent in water of 31 to 60 fathoms in depth, and 23.6 percent in waters of more than 60 fathoms. 3. During the 10-year period, the productive areas amounted to 54.3 percent of 6,531 square miles of shallow area (0-30 fathoms), 51.3 percent of the medium-depth area (31-60 fathoms) of 9,121.5 square miles, and 37 percent of the area of 6,501 square miles of deep area (61 to 125 fathoms). 4. The relative abundance of each species of groundfisli in each depth zone was determined from 5,437 standard otter trawler days of fishing, land- ing 92,201,000 pounds of groundfish from 1932 to 1938 inclusive. 5. The shallow zone was the center of abundance for blackback, lemon sole, and yellowtail flounders. The medium zone was the center of abundance for scrod cod (1}^ to 2K pounds). The deep zone was the center of abundance for ocean perch, cusk, gray sole, pollock, hake, and dabs. Halibut, wolffish, haddock, and cod of more than 2)i pounds did not differ widely in abundance between depth zones. 6. Because of the differences in relative popula- tion densities between depth zones, the catch per unit of fisliing effort cannot be used as a measure of ahundance for most of the species, unless it is tabulated by depth zones. 7. In order to obtain usable indexes of abund- ance for certain of the species, it may first be 278 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE necessary to obtain accurate estimates of the area occupied in each depth zone to permit proper weighting of the index for eacli depth zone accord- ing to the proportion of the population represented. This areal distribution cannot be obtained from the records of the commercial fishery. Therefore, final abundance indexes depend upon surveys of distribution by a research vessel. Such data have been obtained for recent years and are in process of analysis. LITERATURE CITED Herrincton, William C. 1948. Limiting factors for fish populations; some theories and an example. No. 9 in A symposium on fi.sh popu- lations. Yale Univ.. Bull. Bingham Ocean. Coll., vol. 11, art. 4, pp. 229-283. RorN.SEFELL, George A. 1948. Development of fishery statistics in the North Atlantic. U. S. Department of the Interior, Fish and Wildlife Service, Spec. Sci. Rept. 47. 27 pp. SnEUECOR, CiEORfiE W. 1940. Statistical methods. Iowa State College, Ames, Iowa. 422 pp. U- S. GOVERNMENT PRrNTING OFFICE 1957 O — 406253 EFFECTS OF ENVIRONMENT AND HEREDITY ON GROWTH OF THE SOFT CLAM (Mya arenaria) By Harlan S. Spear and John B. Glude, Fishery Research Biologists The relation of the soft, or soft-sliell, clam {Mya arenaria) to its environment is sucli that some flats are favorable for seed-clam production and are not favorable for growth, while the reverse is true of otlier flats. This situation has resulted in the practice of transplanting clams from "seed" areas to "growth" areas, in order to take full advantage of both environments. Obviously it is desirable to know the relative effects of heredity and environment on the growth of the clams; if heredity has the greatest influence it would be desirable to select clams for transplanting from fast-growing stocks, whereas if environment is the dominant factor any convenient source of seed may be used with equal success. The relative efi"ects of stock origin and growth en- vironment, on clam growth, therefore constitute a subject of commercial importance as well as a subject bearing on tlie biological problem of heredity versus environment, or "nature versus nurture." The growth rate of the soft clam varies along the New England coast (Turner 1948); in general, growth is slower in the more northerly and colder areas. In addition, there are local variations in growth rate not obviously caused by water temperatures. The experiment described here was designed to provide information on tlie relative effects of heredity and environment on the growth rate of soft clams. Assistance in the field work of this experiment was provided by Richard E. Tiller, formerly of the Fisli and Wildlife Service, and by Dana Wallace and John Hurst, of the Maine Department of Sea and Shore Fisheries, which cooperated in the experiment. David W. Calhoun, formerly of the Fish and Wikllife Service, assisted in tiie statistical analyses. The Clam Investigations stafl^ of the U. S. Fish and Wildlife Service has been studying the pro- ductivity of Sagadahoc Bay on Georgetown Island, Maine, in terms of the numbers of clams that can be removed annually without causing depletion. The annual clam census, conducted as a part of these studies, has shown that clams in the main part of Sagadahoc Bay grow much faster than those in Bedroom Cove, an adjacent part of the bay (fig. 1). Figure 2 shows comparative growth rates for the main part of Sagadahoc Bay and for Bedroom Cove, as determined by interpretation of rings on the shells.' Tlie reason for the difference in growth rates of clams in the two parts of Sagadahoc Bay must be known for efficient management of the resource. One possible reason is heredity, that is, that the clams in Bedroom Cove are a slow-growing race while those in tlie center of Sagadahoc Bay are a fast-growing race. Another possible reason is that a combination of factors makes the environment in the center of the bay conducive to rapid growth, whereas the environment in Bedroom Cove permits only slow growth. If growtli rates differ because of heredity, a management plan to increase produc- tion might include replacing the slow-growing stock with fast-growing clams; if dift"erences in growth rates are due to environment, the best management plan miglit be to harvest the clams from Bedroom Cove at a smaller size tiian those in the center of the bay, or to transplant them to areas where they would grow faster. Several researchers have discussed tiie causes of variations in the growth rate of soft clams. Mead (1900) observed tliat clam growth depended di- rectly upon the supply of microscopic organisms in the water. Kellogg (1905) indicated tliat dam growth depended on the amount of available food I Speai. llarlnn S., iy.'i4. Rtsulls of poiJUlntlon ci'nsu.s. Sapadahoc Buy. Maine. lin|)iil)lishcil report on file at V. S. Fishery Laboratory. Boothbay Harbor. Maine, 279 280 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE CP I < I I I \A \/i M \ statute Miles P^UiURE 1. — Sagadahoc Bay, Georgetown Island, Maine. ENVIRONMENT AND GROWTH OF THE SOFT CLAM 281 80 2 60 40 I t- o 20 CENTER SAGADAHOC BAY 12 3 4 5 6 AGE IN YEARS FiGORE 2. — Comparat ive growth rates of soft clams from center of Sagadahoc Bay and from Bedroom Cove. ami that etingli()use Cove is a silty area in the Medoniak River system; seed clams are extremely abundant there and the growth rate is low, but better than in Bedroom Cove. 282 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE Figure 3. — Location of test areas and origin of test clams along the New England coast. ENVIRONMENT AND GROWTH OF THE SOFT CLAM 283 Table 1. — Average growth of clams in test areas [Values based on samples taken November 1951 to March 1952] Tested in— Soil type Transplanted from- Soil type Date Initial planted length mt Mm. Feb. 28 26.9 Mar. 1 27.5 Mar. 1 33.7 Mar. 1 29.3 Feb. 28 26.6 Mar. 2 27.8 Mar. 2 32.2 Mar. 2 28.9 Mar. 7 33.4 Mar. 7 28.9 Mar. 7 36.1 Mar. 7 32.0 Apr. 2 25.0 Apr. 2 26.8 Apr. 2 21.3 Apr. 5 26.0 Apr. S 25.6 Apr. 5 35.0 Mean growth Proportion recovered alter 1951 growing season Bedroom Cove. Sagadahoc Bay Rohinhood Cove. Falls Cove Plum Island Sound Sandy silt. Sand Silt Gravelly silt . Sandy silt Western Beach Meetinghouse Cove. Sagadahoc Bay Bedroom Cove Western Beach Meetinghouse Cove. Sagadahoc Bay Bedroom Cove Western Beach Meetinghouse Cove.. Sagadahoc Bay Bedroom Cove Western Beach , Meetinghouse Cove. Falls Cove Western Beach Meetinghouse Cove. Plum Island Sound - Sand Silt- Sand-- Sandy silt Sand-. Silt Sand--- - Sandy silt Sand-- - Silt --.. Sand.-- Sandy silt Sand Silt Gravelly silt. Sand Silt -- Sandy silt Mm. 3.99 6.18 2.42 3.55 17.09 20.30 14.48 18.36 14.69 18.03 11.74 16.21 2.26 3.87 2.85 ' 19.03 > 19. 14 ' 19. 69 Percent 56.0 50.7 56.7 50.0 38.7 24.7 67.3 40.7 3.2 7.6 5.4 5.6 31.3 66.7 6.5 ' Growth at Plum Island Sound is based on shell readings of clams that were dead at time of recovery. To increase the geographical scope of the experi- ment, additional experimental plots were estab- lished in Robinhood Cove and Falls Cove in -Maine, and in Plum Island Sound in Massa- chusetts (fig. 3). The design of the experiment is summarized in table 1. EXPERIMENTAL PROCEDURE Soft clams with an approximate lengtii of 25 mm. were used in the experiment. This initial length was chosen because clams near this size were available in all areas and because (the growth rate of small clams being rapid) differences between areas or plots would be greater than if large clams had been used. Another reason for choosing clams about 25 mm. long was that growth rates would be comparable with those listed by Belding (1930). Each clam was marked with Volger's opaque ink to ensure identification of origin. Previous experiments have shown that this ink remains visible on transplanted clams for a period of 2 to 4 years. Origins were designated by symbols in red or black ink so placed as to cover check marks on the shells that niiglit later be confused with the planting check. Care was taken to avoid injury from contact of the ink with the mantle or other soft parts. Clams from each origin were planted in a separate row containing 13 plots spaced 1 yard apart. Twelve of these plots were 1 stjuare foot in area and contained 50 clams each, for monthly .samples. The thirteenth plot in each row was approxinuitely 4 square feet in area and contained a reserve supply of about 200 clams. 409441 O— 57 2 The rows were parallel, 1 yard apart, and so located that all plots were at the same tidal level and were exposed to the same tidal current. All clams were carefully inserted part way into the substrata to prevent them from being washed away before they became established in the sediment. In discussion of the experiment, each row containing clams from a single origin is termed a "group". One plot from each row in Sagadahoc Bay and in Bedroom Cove was dug each month during 1 year. The high mortality of test clams in the other experimental locations prevented adequate sampling during the entire year, but monthly samples were taken as long as survival permitted. At the time of recovery, all clams were meas- ured to the nearest millimeter with vernier calipers for planted length and total length. The planted length was determined by measuring the length of clams at the check mark on the shell caused by transplanting. Mean growth for each plot was computed from the planted and total lengths. Summaries of growth, by montlis. in the five test areas are given in appendix A; the mean growth for each area, based on select "d samples, is shown in table 2. 284 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE T.\BLE 2. — Mean growth of clams in five test areas, based on selected samples Test area Mean powth Number of clams on which mean growth is based Mm. 3.99 16.84 15.49 3.28 19.35 320 276 Robinhood Cove. . 109 Fnlls Cove 160 Plum Island Sound . . 331 ANALYSIS OF RESULTS SURVIVAL Survival of planted clams at Bedroom Cove and Sagadahoc Bay was high enough that sufficient clams remained after the 1951 growing season to provide reliable growth data. The proportion recovered from plots dug in December 1951 and in January, February, and March, 1952, ranged from 24.7 to 67.3 percent, as shown in table 1. The survival at Robinhood Cove was very poor; only 3.2 to 7.6 percent of the planted clams were re- covered after the 1951 growing season. Green crabs, Carcinides maenas, wliich are serious pre- dators of clams, were very abundant in Robinhood Cove and are believed to have been responsible for the poor survival of planted clams. It was necessary to use clams from the supplementary plots to provide enough measurements for analysis of the growth. Clams from Meetinghouse Cove survived satis- factorily when planted at Falls Cove, as indicated by a recovery of 66.7 percent after the 1951 grow- ing season. Of the Western Beach clams planted at Falls Cove, 31.3 percent were recovered during the winter of 1951 and 1952, but survival of native Falls Cove clams replanted in the experimental area was extremely poor. On November 16, 1951, all of the monthly plots and the supplementary plot were dug, and only 13 live clams were re- covered. The poor survival of Falls Cove clams is believed due to their small size, which made them more susceptible to injury from the marking ink used on their shells. If Volger's opaque ink touches the mantle or siphon of the clam it will injui-e the tissues. Since these clams were smaller than those in any other group, the cliances of injury from this source were greater. The growth of Falls Cove clams that survived was intermediate between that of the Western Beach clams and that of the Meetinghouse Cove clams planted at Falls Cove, which had a much higher rate of survival. If the marking ink was the cause of the mortality, it appears that it did not affect the growth rate of the clams that survived. It is likely that the initial size of 21.3 mm. given in table 1 for native clams replanted at Falls Cove is somewhat higli because it is based on shell measurements of the 13 clams recovered at tlie end of the experiment. Many of the clams planted in the spring of 1951 were 12 to 16 mm. long and had the thin shells characteristic of clams of this size. It therefore appears likely that the marking ink was the cause of the poor survival. It was unfortunate that clams closer to the desired planted size of 25 mm. were not available at this location. Each group of clams planted at Plum Island Sound had a mortality of 100 percent during the late summer and autumn of 1951. Before this time, however, these clams had grown at an extremely rapid rate, as shown in table 1. If we can assume that there was no differential mortality among the three groups, the measurement of growth from the shells of dead clams can be used in the analysis. Since the total mortalities of the three groups were identical and since growth rates were nearly identical, varying only from 19.03 to 19.69 mm., it is likely that inclusion of these data will not cause any significant error in the analysis. In fact, the conclusions are the same whether or not this group is included in the analysis. The percentage recovery after the 1951 growing season shown in table 1 is a rough indication of survival, and is based on the number of clams dug from plots during the winter of 1951-52. It is not a true measure of survival, since it does not take into account the clams that moved, or were moved by hydrographic forces, away from the planting location. Frequently, clams planted in one row were recovered in other rows. Sample digging in the vicinity of the test plots also showed that the marked clams had spread over a considerable area. Therefore, the percentage recovery listed in table 1 might be considered as a minimum percentage survival. INITIAL SIZE All clams obtained from each source for use in this experiment were dug at the same time and had a common mean length, regardless of the area to which they were transplanted. At the time of ENVIRONMENT AND GROWTH OF THE SOFT CLAM 285 recovery, however, the initial length, based on measurement of the check-mark on the shells caused by the transplanting, varied among test areas. In each case, the clams recovered from plantings at Robinhood Cove had a greater initial lengtli tlian those from corresponding groups in the other test areas. It is likely that the smaller clams planted at Robinhood Cove were eaten by green crabs (these smaller clams were nearer the surface of the flats), which resulted in a greater initial length of clams recovered in this area. GROWTH Mean growth shown in table 1 is based on the difference between total length and initial, or "planted," length of each clam as determined at the time of recovery. Monthly samples taken during the winter of 1951-52 were combined to provide an adequate sample for statistical analysis. Combining these samples was justified by the fact that there is virtually no growth during this period, as shown by figures 4 and 5. The mean growth rates of test clams ranged from 2.26 mm. for a group at Falls Cove to 20.30 mm. for a group at Sagadahoc Bay. Table 1 and figures 4 and 5 show that there is a tendency for growth rates to vary less within each test area than between test areas. At Bedroom Cove the native clams grew only 3.55 mm., but clams trans- planted from three other origins also grew slowly. At Sagadahoc Bay the clams from the same origins as those planted at Bedroom Cove grew several times as much. At Robinhood Cove all groups grew much faster than did those at Bedroom Cove. Native clams at Falls Cove averaged only 2.85 mm. growth, and those transplanted from Meet- inghouse Cove and Western Beach also grew very slowly. Contrast this with Plum Island Sound, where clams from Meetinghouse Cove and Western Beach grew more than 19 mm. Statistical analyses (described in appendix B) show that the differences in mean growth between test areas are highly significant. It is safe to conclude that clams from a common origin adopt CENTER SAGADAHOC BAY ..a MAR APR MAY JUNE JULY Aue SEPT OCT NOV DEC JAN FEB MAR BEDROOM COVE FinuKE 4. — Growth curves for groups of dams planted in Sagadahoc Bay and in Bedroom Cove, .smoothed by moving averages of three. Origin of clams was as follows: 1, Western Beach; 2, Meetinghouse Cove; 3, Sagadahoc Bay; 4. Bedroom Cove. 286 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE ROBINHOOD COVE —1 1- FEB MAR APR MAY JUNE JULY AUG SEPT 1 OCT NOV 1 D EC JAN FEB MAR FALLS COVE Figure 5. — Growth curves for groups of clams planted in Robinhood Cove and in Falls Cove, smoothed by moving averages of three. Oiigin of clams was as follows: 1, Western Beach; 2, Meetinghouse Cove; 3, Sagadahoc Bay; 4, Bedroom Cove. significantly different growth rates when trans- planted to areas of different growth conditions. The importance of environment as opposed to heredity in affecting the growth rate of clams is emphasized by these results. If heredity were the cause of the differences in growth rates in various areas, we should expect clams that grew fast in their native beds to continue to grow fast when transplanted. Likewise, slow-growing clams would be expected to continue their slow rate of growth after transplanting. Instead, the growth rates of clams in this experiment varied with new environments. For example, Bedroom Cove clams, which grew only 3.55 mm. in their native environment, grew 18.36 mm. in Sagadahoc Bay. At the same time, Sagadahoc Bay clams, which grew 14.48 mm. in their native area, grew only 2.42 mm. when transplanted to Bedroom Cove. EFFECT OF ORIGINS ON GROWTH RATES Analysis of variance tests by areas (see appendix B, table B-2) also show that there are significant differences in the mean growth of groups of clams within each test area. This result might be expected because of the spread in the growth curves (figs. 4 and 5). The growth curves for clams from Meetinghouse Cove were higher than for other groups in each of the four test areas where these clams were planted. The analysis of variance summarized in appendix B, table B-3, shows that the F value was reduced from 13.0 to 6.0 by omitting clams from Meetinghouse Cove. It is also apparent that Sagadahoc Bay clams contributed greatly to the differences within each test area because their grow^th rate was consistently lower than that of the other groups. Since clams from Meetinghouse Cove appeared ENVIRONMENT AND GROWTH OF THE SOFT CLAM 287 to have grown faster than any other group in each test area except Plum Island Sound, the differences in mean growth were analyzed by origins instead of by test areas. Differences between mean growth of groups of clams from different origins were not statistically significant, as shown by table B-4 in appendix B. Although not statistically significant, the ap- parently faster growth of Meetinghouse Cove clams in four test areas suggests another factor in the experiment. Clams in Meetinghouse Cove have a history of slow growth. If this were a hereditary or racial characteristic, we should expect them to grow slowly after being trans- planted to other areas. Instead, the growth rate of Meetinghouse Cove clams was numerically greater than that of clams transplanted from other origins. On the other hand, native clams in the center of Sagadahoc Bay have a record of fast growth (fig. 2), as indicated by a growth of 14.48 mm. during the present experiment (table 1). In the three test areas where these clams were planted, however, their growth was numerically, although not statistically, less than that of any other group. As far as heredity is concerned, these clams would be expected to have grown fast after transplanting. Since they grew slowly, it is likely that a factor other than heredity was responsible. EFFECT OF PREVIOUS ENVIRONMENT A possible explanation for the fast growth of Meetinghouse Cove clams and the slow growth of Sagadahoc Bay clams after transplanting is the effect of their previous environment. Meeting- house Cove is a shallow, silty cove on the west side of the Medomak River estuary. Tidal currents are slow, and this area is protected from current -inducing winds by the surrounding hills. There is a high concentration of slow-growing clams in this area, and competition for food must be extreme. Sagadahoc Bay is a wide, sandy area exposed to the south winds. Both tidal and wind-induced currents are strong. The clam population consists of a few well-scattered, fast-growing individuals. Competition for food is not likely to be a factor influencing growth in this area. Perhaps competition for food causes clams in Meetinghouse Cove to feed more actively or efficiently than those in Sagadahoc Bay which have an abundance of food. If this characteristic persisted after the clams were transplanted to new areas, the Meetinghouse Cove clams might be expected to grow faster and the Sagadahoc Bay clams slower, as was observed in the experiment. SUMMARY 1. The objective of the experiment was to determine whether differences in growth rates of soft clams in two parts of one bay (Sagadahoc Bay) were caused by environment or by heredity. This determination is an economically important consideration in clam transplantation. 2. Test areas were established at five locations along the coast of New England, including the two parts of Sagadahoc Bay. Native clams and clams from two to four other sources were planted in each location. 3. Growth during one growing season was measured by monthly sampling. 4. Good survival resulted at Sagadahoc Bay and Bedroom Cove and in two of the three groups planted at Falls Cove. Survival was poor at Robinhood Cove because of depredation by the green crab, Carcinides maenas. For unknown reasons clams died in Plum Island Sound during the late summer. 5. Mean growth for clams in each test area was as follows: Bedroom Cove, 3.99 mm.; Sagada- hoc Bay, 16.84 mm.; Robinhood Cove, 15.49 mm.; Falls Cove, 3.28 mm.; Plum Island Sound, 19.35 mm. 6. Differences between mean growths in tlie five test areas were highly significant, as shown by analysis of variance. Clams from a single origin grow at significantly different rates when trans- planted to different environments. 7. Differences between growth rates of groups of clams from different origins within each test area were not statistically significant. Therefore, clams from different origins assume similar growth rates when transplanted to a single enviroimient. 8. Although not statistically significant, the numerically faster growth of Meetinghouse Cove clams, and the slower growth of Sagadahoc Bay clams in all cases except one, suggest anotlier factor influencing growth. A tentative explana- tion is the effect of previous environment, which caused clams from a slow-growing area (Meeting- house Cove) to grow fast, and clams from a fast- growing area to grow slowly after transplanting. 288 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE Because the observed growth pattern was the opposite from that which would have been expected if heredity were the principal factor determining growth, the conclusions of the experi- ment are not altered. 9. The experiment demonstrated that environ- ment, not heredity, was the important factor in determining growth of the soft clam. LITERATURE CITED Belding, David L. 1930. The soft-shelled clam fishery of Massachusetts. Massachusetts Department of Conservation, Division of Fisheries and Game, Marine Fisheries Series — No. 1. 65 pp. Kellog, James L. 1905. Conditions governing existence and growth of the soft clam (Mya arenaria). U. S. Commission of Fish and Fisheries, Report of the Commissioner for 1903, pp. 195-224. Mead, A. D. 1900. Observations on the soft-shell clam. Rhode Island Commissioners of Inland Fisheries, 30th Annual Report, pp. 20-42. Newcombe, Curtis L. 1935. Growth of Mya arenaria in the Bay of Fundy region. Canadian Journal of R<>search, vol. 13, sec. D, No. 6 (December), pp. 97-137. QUENOtriLLE, M. H. 1950. Introductory statistics. Ltd., London. 248 pp. Butterworth-Springer Snedecor, George W. 1946. Statistical methods. Iowa State College Press, Ames, Iowa. 4th ed. 485 pp. Turner, Harry J., Jr. 1948. Report on investigations of the propagation of the soft-shell clam, Mya arenaria. Massachusetts Department of Conservation, Division of Marine Fisheries (also Woods Hole Oceanographic Institution, Contribution No. 462), pp. 11-42. APPENDIX A— ORIGINAL DATA NUMBER RECOVERED AND AVERAGE GROWTH, BY MONTHS, OF CLAMS TRANSPLANTED IN FIVE TEST AREAS Table A-1. — Bedroom Cove test area [Samples collected on dates marked by asterisks were used in statistical analysis and to obtain mean growth 0(3.99 mm. based on 320 clams] Date sampled Clams transplanted from— Western Beach Meetinghouse Cove Sagadahoc Bay Bedroom Cove Number recovered Average growth Number recovered Average growth Number recovered Average growth Number recovered Average growth April 2 1961 44 37 42 41 33 34 21 19 30 26 28 Mm. 0.0 .3 .2 .9 1.8 2.7 3.8 4.3 3.7 4.3 4.0 22 35 34 31 33 28 20 26 30 21 25 Mm. 0.4 .6 1.1 1.9 3.9 4.3 3.6 5.8 6.0 6.9 5.8 26 31 42 38 32 28 32 30 27 26 32 Mm. 0.0 .2 .4 1.0 1.9 1.9 1.8 2.7 1.6 3.0 2.7 36 36 39 42 38 29 34 25 29 21 25 Mm. Mays... _ 1 June6 1.2 July 5 1 9 August 10 ,__ 2.5 2L9 October 1 3 1 Novembers 3.4 2.9 January 20* mt 3.3 February 26* 4.5 Table A-2. — Sagadahoc Bay test area [Samples collected on dates marked by asterisks were used in statistical analysis and to obtain mean growth of 16.84 mm. based on 276 clams] Clams transplanted from— Date sampled Western Beach Meettoghouse Cove Sagadahoc Bay Bedroom Cove Number recovered Average growth Number recovered Average growth Number recovered Average growth Number recovered Average growth I9S1 April 2 27 44 18 28 16 21 22 10 33 19 25 Mm. 0.0 .5 4.6 7.1 13.7 14.6 17.4 19.8 16.9 15.7 18.4 25 41 21 8 15 18 17 10 11 15 11 Mm. 0.0 1.0 5.5 8.5 14.2 18 5 21.1 17.4 20.0 21.1 19.4 31 42 35 35 42 34 19 22 35 27 39 Mm. 0.0 .5 3.3 6l0 9.7 11.3 14.1 11.5 14.6 15.3 ia8 46 27 24 20 33 25 26 25 27 13 21 Mm. 0.0 May3 _ .5 June 6 __ 4.0 June 26 8.5 August 10 13.9 September 12 16.1 October 1 17.5 18.1 December 4* 16.9 wet January30*.. 18.2 March 11* 20.3 Table A-3. — Robinkood Cove test area [Samples collected on date marked by asterisk were used in statistical analysis and to obtain mean growth of 15.49 mm. based on 109 clams] Clams transplanted from- - Date sampled Western Beach Meetinghouse Cove Sagadahoc Bay Bedroom Cove Number recovered Average growth Number recovered Average growth Number recovered A verage growth Number recovered Average growth 1961 April 2 40 41 28 18 10 11 16 Mm. 0.0 .6 2.7 5.5 8.4 17.4 14.7 40 40 27 21 4 10 38 Mm. 0.0 7.0 9.6 18.2 l&O 42 36 22 20 6 10 27 Mm. 0.0 .4 .6 4.1 3.0 12.0 11.7 45 40 » 14 6 12 28 Mm. 0.0 Mav4.. .4 June 4 1.6 July 2 5.2 AuBust9 7.6 September 12 14.6 December 7* 16.2 289 290 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE Table A-4. — Falls Cove lest area [Samples collected on dates marked by asterisks were used in statistical analysis and to obtain mean growth of 3.28 mm. based on 160 clams] May 2 June 9- July 6 August 7 September 13 - October 15- -.. November 16* . December 11*. . March 19. Date sampled wee Clams transplanted from — Western Beach Number recovered 87 A verage Rrowth Mm. 0.0 1.4 1.4 3.1 2.0 2.3 2.5 2.1 2.6 Meetinghouse Cove Number recovered 62 Average growth Mm. 0.1 1.9 3.1 2.7 3.2 3.1 3.7 3.9 Falls Cove Number recovered Average growth 0.3 1.2 .8 3.8 1.0 2.8 Table A-5. — PUim Island Sotmd test area (Samples collected on date marked by asterisk were all recovered dead but were used in statistical analysis and to obtain mean growth of 19.3.'j ram. based on 321 clamsj Clams transplanted from- - Date sampled Westem Beach Meetinghouse Cove Plum Island Sound Number recovered Average growth Number recovered Average growth Number recovered A verago growth 19S1 April 30 34 30 9 3 1 3 77 Mm. 1.2 8.9 18.3 27.0 20.0 31.7 19.0 41 36 33 26 1 95 Mm. 1.3 10.4 18.0 23.6 33.0 45 36 34 10 3 2 149 Mm. 1.7 May 31 July 2 _ __:.. 9.9 17.0 August 3 -■•.-. 22.7 Septen ber 7 ,. . . .... 23.0 28.5 December 4' 19.1 19.7 APPENDIX B.— STATISTICAL ANALYSIS ANALYSIS OF VARIANCE BETWEEN AND WITHIN TEST AREAS Standard deviations for the 18 groups of clams plotted against their means follow a straight line having the formula E= 1 .15 + 0.284A' (fig. B-1 and table B-1). The slope of this line indicates the need for transformation to make variances independent of the means in order that methods for analysis of variance shall become applicable. The fact that standard deviations plotted against means follow a straight line indicates that the log transformation is the one to be used (Quenouille 1950). Figure B-2 shows tiie variance plotted against the mean for each of the 18 groups of clams after the values had been transformed by taking the log of the midpoint of each '2-mm. class plus 1 (table B-1). The very sliglit slope of the least- squares line, as indicated by the formula E— 0.077 — 0.0304A', indicates that the variances have been made virtually independent of the means. Analysis of variance can therefore be completed, using the transformed values. Table B-2 shows the completed analysis of variance of differences in mean growth between and within test areas using transformed values. The F value for a comparison of between and within test areas was 43.9, which is highly signifi- cant. This indicates that differences between growth rates in the various test areas are liighly significant. A comparison of the differences within test areas and between individuals yielded an F value of 13.0, which is also highly significant. This indicates that there is a considerable amount of variation among the groups of clams that were used in the various test areas. It appears likely from examination of the untransformed mean growths in table 1 (in text) and from the growth curves in Hgiires 4 and 5 (in text) that Meeting- house Cove clams are largely responsible for the high F value in this test. ENVIRONMENT AND GROWTH OF THE SOFT CLAM 291 T.\Bi.E h-\. — Original and transformed mean, variance, and standard deviation for growth of 18 groups of clams in i-mm. classes used in figures B-1 and B-2 [Transformation is based on formula; Transformed X = log (class midpoint + U. Total number of clams, 1,186) (Jroup code letter OrtKin Test area Number of clams Original arithmetic mean (mm.) Original standard deviation (mm.) Trans- formed arithmetic mean Trans- formed variance Bedroom Cove 84 76 85 75 61 101 37 77 28 il 16 ICO 13 47 77 149 95 4.02 6.15 2.36 3.57 18.50 14.58 20.01 16.99 16.14 11.76 18.08 14.62 3.96 2.81 2.37 18.94 19.72 19.15 2.87 2.72 2.13 2.38 5.21 ,'j.54 6.49 .5.43 6.97 3.69 4.37 5.87 1.77 1.60 1.78 9.17 6.67 6.63 0.625 .813 .441 .591 1.274 1.159 1.297 1.233 1.172 1.085 1.268 1.138 .666 .534 .463 1.237 1.283 1.289 0.073 do .045 c D E do .075 do .068 do Sagadahoc Bay - .015 do --- .033 Q do -.- .026 H Western Beach do - .021 Robinhood Cove .081 J ...do - .021 do - Oil do - .082 M Falls Cove .028 Falls Cove do .050 do .-. - -- .060 do Plum Island Sound .075 _ _. Plum Island Sound -- do --- -- do - .040 s 7 8 9 10 MEAN GROWTH II IN 12 M M 13 14 15 17 18 19 20 21 Figure B-1. — Standard deviation plotted against arithmetic mean growth for 18 groups of clams listed in table B-1. The slope of the trend line fitted b.v least-squares method indicates the need for transformation to make anal.vsis of variance applicable. o UJ z cr < < cr > .2- Less t Squares Line E= 0.077— 0.0304 X —I 1 1 1 1 1 1- .5 .6 .7 .8 .9 1.0 I.I TRANSFORMED MEAN GROWTH 1.2 1.3 1.4 1.5 1.6 Kif:rRE B-2. Variance plotted against aritlinictic mean growth for 18 groups of clams listed in table B-1 after growths were grouped in 2-inni. classes and transformed by taking the log of each class midpoint plus one. The extremely slight slope of the trend line fitted by the least-squares method indicates that this transformation has made variance slight slope virtually independent of the mean, so analysis of variance method can be used. 292 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE Table B-2. — Completed analysis of variance of differences in mean growth between and within test areas Itased on 18 groups of clams at 5 areas ll'sinB values transformed by the formula: Transformed .Y = log (midpoint of 2-mm. class + 1)] Source of variation Degrees of free- dom Sum of squares Mean squares F Between test areas - Within test areas 4 13 1,168 114.09 8.44 53. 02 28.52 0.65 0.05 •'43.9 Between individuals "13.0 Total 1,185 176. 15 The analysis of variance by test areas was recomputed without the groups of clams that came from Meetinghouse Cove; the results are listed in table B-3. While the differences in mean growths of groups within tlie test areas are still highly significant, the F value has been reduced from 13.0 to 6.0 by exclusion of Meeting- house Cove clams. Therefore, it appears that clams from this origin were responsible for more than half of the F value of 13 listed in table B-2. Also, it appears likely that the clams from Saga- dahoc Bay contributed a large part of the high F value for this test (figs. 4 and 5). Since the growth pattern of both the Meetinghouse Cove Table B-3. — Completed analysis of variance of differences in mean growth between and within te^l areas ttased on IS groups of clams (excluding those from Meetinghouse Cove) at 5 areas (Using values transformed by the formula: Transformed X= log (midpoint of 2-mm. class + 1)] Source of variation Degrees of free- dom Sum of squares Mean squares F Between test areas. 4 8 827 93.32 2.43 42.17 23.33 0.30 0.06 Within test areas. ••77. 77 "6.00 Total 839 137. 92 clams and the Sagadahoc Bay clams was the opposite of that which might be expected had heredity been the cause of growth differences and growth rate, the significance of this F value does not alter the conclusions given here. ANALYSIS OF VARIANCE BETWEEN AND WITHIN ORIGINS The possibility that variation between the se- ries means was caused by the origin of the test clams needed to be explored. Mean growths of clams from the four origins planted at Bedroom Cove, Sagadahoc Bay, and Robinhood Cove were used in this analysis, because only at these three test areas were all four groups planted. Results of the analysis-of-variance tests are shown in table B-4. The F value of 8.42 for a comparison between origins and within origins was not significant at the 5-percent level. There- fore, the effect of the origin of the clams on their growth rate after transplanting was not significant. The F value of 166.8 for a comparison within origins and between individuals was highly sig- nificant, indicating (as would be expected) that the differences in mean growth of clams from each origin planted in the three test areas were highly significant. T.'^BLE B-4. — Completed analysis of variance of differences in mean growth between and within origins of clams based on 12 groups of clams from 4 origins [Using values transformed by the formula: Transformed X = log (midpoint of 2-mm. class + D) Source of variation Degrees of free- dom Sum of squares Mean squares F Between origins Within origins 3 8 693 2.97 66.74 31.92 .99 8.34 0.05 8.42 ••166.8 Total 704 101. 63 U.S. GOVERNMEt.T PRINTING OFFICE 1957 O — 409441 CLIMATIC TRENDS AND THE DISTRIBUTION OF MARINE ANIMALS IN NEW ENGLAND By Clyde C. Taylor, Fishery Research Biologist, Henry B. Bigelow, Oceanographer, and Herbert W. Graham, Fishery Research Biologist For many years Americans have commented on an apparent warming of their climate; older people have referred to the "old-fashioned winters" they once knew. Climatologists long shrugged off the idea as unfounded, but a melioration in climate is no longer confined to the popular mind : a decided trend toward warmer winters during the past 50 years is now well-documented. Air temperatures in winter, particularly since 1910, are definitely higher in higher latitudes of the Northern Hemi- sphere and probably throughout the world gen- erally. Glaciers have been receding and in far northern latitudes, plants and land animals fol- lowing the retreating ice have extended their ranges northward and to higher altitudes. P'or a bibliography dealing with responses of plants and animals to climatic changes, the reader is referred to Rapports et Proces-Verbaux des Reunions, vol. 125, pp. 42-52, C'onseil Permanent Inter- national I'Exploration de la Aler, Part 1, 1949. Warming of the oceans during periods of higher air temperatures is difficult to demonstrate because of the paucity of observations of sea-water temperatures. Evidence shows, however, as Smed (1949, 1953b) points out, that the Arctic Ocean has warmed appreciably since 1921. This author also presents evidence of increased water temper- atures beginning in the 1920's in the North Sea and in the North Atlantic from the British Isles to the west coast of Greeidand. The warming of northern waters has been ac- companied by the northward extension of many marine vertebrates to the region of Iceland (Fridriksson 1949) and by profound changes in the fish populations around Greeidand (T;\ning 1949). The development of tlie cod fisliery on tlie west coast of Gicenland has been spectacular. As the Note.- Clyde C. Taylor ami llcrbiTl W. Graham, United States Fish and Wildlite Service, Woods Hole. Mass.; Henry B. BiRelow, Museum of Compi',rativ<' Zoology, Harvard I'niversity. Approved for publication, November 1, 1956. waters warmed in this area, an offshoot from the Icelandic stock of cod became established and now supports a substantial fishery (Jensen and Hansen, 1931). In the years 1911 to 1921, the West Greenland cod fishery produced less than 500 tons a year. In 1925, the catch doubled and thereafter continued to increase. In 1952, some 252,758 metric tons of cod were landed from the West Greenland area (International Gommission for the Northwest Atlantic Fisheries, 1954, table 2, p. 28). The fishery now reaches 300 nautical miles farther north than formerly. The Eskimos in some areas who had never seen a cod in 1924 are now busily occupied in the cod fishery, whereas they formerly were seal hunters. Although temperature is only one factor in the ecological complex determining the presence or abundance of a species, in high latitudes temper- ature may in some instances be the sole limiting factor and have a direct effect on distribution. Thus, cod show a definite response to low tempera- tures and their northward extension is probably determined by temperature alone. The abundance of cod in the Greenland area may be related to temperature in a somewhat less-direct manner. Hermann (1953) has shown that the strength of cod year-classes in Greenlaiul waters has a very high correlation witli bottom temperatures in June. Thus, temperature in some way affects survival of whole populations of young fish, per- liaps through affecting their food supply or rate of growth and, conseciuently, their resistance to adverse enviromnental conditions. The warming of arctic areas and the accompany- ing ecological changes have been so marked and so well-documented tliat it seems reasonable to suppose that similar changes liave taken place, although perliaps on a smaller scale, in more southern latitudes. It is the purpose of this paper to examine temperature fluctuations in recent years, and to explore the relations which may 293 294 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE exist between these fluctuations and the abundance and distribution of marine animals along the eastern coast of the United States and in the New England area, in particular. In the following pages we present some of the available data on trends in air and sea tempera- tures and trends in the distribution of certain species of marine fish and invertebrates. We are aware that, in some instances, we may be mis- interpreting the causes of observed changes, or even may be misled in believing that some of the changes have occurred. It is hoped that the pres- entation of these relationships will stimulate others, especially specialists in particular fields, to examine more critically the data tliey may have at hand. A great deal of the theory of fishery science i