I REPORT OF INVESTIGATIONS OF SKIPJACK AND TUNA RESOURCES Marine Biological Ubc.iOiJ 3^ 133 it A. ri -sr MAY 2 3 1950 WOODS HOLE, MASS. ^ SPECIAL SCIENTIFIC REPORT: FISHERIES No. 17 1 UNITED STATES DEPARTMENT OF THE INTERIOR FISH AND WILDLIFE SERVICE REPORT OF INVESTIGATIONS OF SKIPJACK AND TUNA RESOURCES Marine Bioloj^ical i.^Doi^ioi ^ X 13 K A jR. -sr MAY 2 3 1950 WOODS HOLE, MASS. J SPECIAL SCIENTIFIC REPORT: FISHERIES No. 17 UNITED STATES DEPARTMENT OF THE INTERIOR FISH AND WILDLIFE SERVICE ' Explanatory Note The series embodies 'results of investigations, usually of restrioted scope, intended to aid or direot management or utilieation practices and as guides for administrative or legislative action. It is issued in limited quantities for the official use of Federal, State or cooperating agencies and in processed form for economy and to avoid delay in publication* Washington, D* C« April 1950 United States Department of the Interior Oscar L. Chapmen, Secretary- Fish and midlife Service filbert M. Day, Director Special Scientific Report - Fisheries No. 17 REPORT OF INVESTIGATIONS OF SKIPJACK AND TDK*. RESOURCES IN 1947 By Nakeunura Research Staff l/ Translated from the Japanese language by W* G* Van Campen Pacific Oceanic Fishery Investigations CONTENTS Preface Page Morphouietric data on skipjack from the Omaezaki area. .... 1 Skipjack resources of the Satsunan area ••••. 6 l/ Fisheries Expertmental Station March 1949i Report of Investigations of Skipjack and Tuna Resoxirces in 194.7 Nakamura Research Staff A number of studies of skipjack were made during this year. No Investigations of tuna could be carried out because of the inadequacy of research vessel facili- tiesc Part I iB a study of the catch from the waters off Oraaezaki, while Part II consists of data on the fishing ground3 of the Satsunan Area which viere collected at Aburatsu. I Morphometric Data on Skipjack (KatBuwjnus pelamis) from the Waters Adjacent to Omaezaki Between August and the middle of October of 1948 length and weight data were collected on about 1,200 skipjack taken from the waters adjacent to (in the vi- cinity of 30 miles SSW of) Omaezaki in Shizuoka Prefecture, On about 60 of these specimens fin ray counts, gill raker counts, and sixteen other determinations were made. The measuremente were made along a straight line between two points by the use cf calipers, and readings ^jare taken to the nearest millimeter. The body length used was the fork length, that is the straight line distance from the tip of the snout to the point of intersection of the posterior edges of the upper and lower lobes of the caudal fin. The data on the fork lengths and the body weights are shown in Table 3o According to the fishermen the fish which are taken in August and September are either fish resident on ahoals or are members of north- bound migratory schools, while the fish taken in October are from schools which are moving southward. The data shown in Tables 1 and 2 (Table 2 shows only a part of the measurements) have been combined on the assumption that all of the fish be- longed to a single ecological and taxonomic group, that is to say, they show only their characteristics as Katsuwonus pelamis. The following cautions are given with regard to the data in Table 1, Depending on the individual, the most posterior spine of the first dorsal may be completely separated from the spine anterior to it with no membrane visible between the two spines. It is not dear at present irtiether this is an individual variation or whether it is the result of damage to the fin membrane. Again depending on the individual fish, it is difficult in many oases to distinguish the first dorsal finlet from the rays of the second dorsal fin, and since the same difficulty is encountered with the anal flnlets and the rays of the anal fin, the number for both of these counts can be found more accurately on these specimens by adding together the counts for the fin rays and the flnlets. In the case of the gill raker count, also, it would be moat suitable to count the upper and lower limbs sepaa^ately, but in actual practice this is almost impossible and so the figures given represent the sum of the gill rakers on both limbs of the arch. (Persons who carrted on the Investigation — Katauao Kuronuma, Takeichiro Kafuku, and Shoji Kogawa.) Table 1 Fin ray and gill raker counts of skipjack (Katsuwonua pelamis) taken in the Tfaters adjacent to Oraaez£.kl in Izu between August and October of 19il7 First Dorsal Spines Dorsal Pin Spines Separate Spines Total Number of Spines 13 U 15 16 0 1 U 15 16 17 Number of Fish 1 3 52 10 O 23 1 39 23 3 Number of Rays Number of Fish Second Dorsal Rays and Finlots 13 6 Rays U 15 54 6 8 3 Finlets 9 61 10 2 22 7 Total 23 53 24 6 Anal Rays and Finleta Rays Finlets Total Numbar of Rays Number of Fish 13 U 15 6 7 11 53 2 10 Pectoral Rays 8 9 64 1 20 21 1 n 22 52 23 2 Number of Rays Number of Fiah 24 3 25 26 27 28 29 0 9 30 19 3 30 31 1 0 32 1 Number of Gill Rakers on First Left Arch Number of Rakers Number of Fish 44 1 45 46 47 48 49 50 0 0 10 0 2 51 52 1 5 53 54 7 8 55 56 13 9 57 7 Number of Rakers Number of Fish 58 7 59 60 61 13 1 «oJ o o ,,^ »^^ r-i -- ta (^ te o ei •»S(' •*"'*• C^^^ t ►7 o4 a-: (1 (T> t ♦-! ::^Tl ^^ a ^ •-«"-' rH--' av^~> -«*'-» fiO CM or- CM • CM e 1 t*> • r^ S CM ^J^ w t >r» 1-4 rH rH w CM- to *~^ H CM r-H » 0 CM O rH <^ • I H rH«) »f\ CM CM*-- CM ,-N vp^^ CM • r;* n^ ?- ,H t- rH a «A I O >OrH Q '-' CM CM O O ^ 9 2 S O C^« to -"-^ (JS-^ flO>-v RT g**: .^x "-"d 0 vO )^R 1 •>* ^'^Sl CO o c> c'n 8^R CM CM (V— ' CM— ' CM—' CM t vO H— ' 3, Sa 1 00 « O « j> C*--' rH — nj— <■ •^ ^ 8^ -. fM*-* r-{> St—' CM" ro n ^ c^co to c^:* H W CV CM OJ v_*< ? 4* 4* ^ c o • 3 9 o e ts a: ^ c -H o c ^-^ U (•> , a -p o d_§ •9 O o o n ^^5 s o i-t ->* «r\ •«* H >0 Q CM 0 V> iH ir> O CM <^tO <*% c% H <*> **» 0^^-«t CM CM m>4 CO CM CM CM «NH ir> »f\CM ^- CM \e\r4 ^»r>CM <«\(*\iHCM r^ •-* 1 JL ■P4?5 ^(» ffi O tf) 01 O 0^ •^<«>C<>iH >t r-t OO ^ r-l C^ f^ c^ • -^ ■sO CM>0 f-l ^ r4 «n iH -^f»^ WN c< H l><*\-* H r- c^ -<* o 'i •p c o o r^ 6-t O^ r^ r-l • M> o «0 CM CM H t-l • <^ o r^ HCfNtONO d NO H CM *r\\0 • o «> iH*f\f\ • o ^ CM H • o f\ iH iH • o CM CM d r^ OJ ■*> rH ^ 1 ir> iH » 1 vO ►« P r^ ^ "^-^JS^,. O Date Aug'ist August Sop torn Septem m r* rA H Nnj:^ NO rH f-lsO <0 • • CMrHNO^ • H >* »AnO 9 H eo <'\ «> CM rN CM • ^"'S;s * ^8^^^' O « to c-no r^to ON • CM ?3JX"^?I8 to A CM iH ^C^ p r- CM CM C^r- • CM J^^S'-^g?" NO • CM JQ^CM>J<^ • CM ^NO^NOrH « CM CT>>nrH urjCM C^ no Nt f^ 0 On »rn nO -^nO cm r-i Cl N r> ' ON to «-i I nO t< tl f^ B s) n c ® o o ■< *; t^ cfti o •t? -p e B « a a • Q ^ O4 o. • ^5 4c8*,S II An Inrostlgatlon of th« Skipjack Resources of the Satsiman Aroa (a) Because there was no research vessel available, these data were gathered aboard eommarclal fishing boatac (b) MeatJurenienta of fresh fish were iiadc at the Aburatsu fish market, and obeerva- tions requiring dissection of the fish ror© made at dried fish-stick factories. (c) Reports of stjitistical data were obtained from the Fisheries Associations of Kagoshlina and Miyaaakl prefectures, and the figiire« were verified insofar as possible by field tripe to those arsaso (d) At Aburatsu and vicinity certain boats i?er« assigned the duty of reporting on the fishing situation, and reports on the designated eubjeots were obtained from these vessels at the conclusion of each flshJjig trip. Data (ft) The skipjack fishing situation in the Satsraan Area in 194-7 (for boats from Miyasaki Prefecture) nw first catch was made near the Shichlto by the Shoei Mara on March 5 ifhen 200 kan C 1 kan z ^.27 pounds} were taken noar Suwaseshiaa C 29°38»N, 129® 43'S 3 . On March B a few fish were caught at GogSzone L 29° 30' M, 129® S' Sj , and on March 12 500 j^n vere taken at Gajanishlsone [29® 55* N, 128® 50' E3 . The final fishing of the season was done in the waters adjacent to the Shichit3 and at Torishina [ 27° 52» N, 1230 U* E3 . Ibronghout the whole season the principal fishing grounds were around the Shichito and on the shoals west of the Amami group, but a peculiar ;^noDdnon was the appearance during a period of about two weeks beginning in the middle of May of dense schools of fish which took the bait extremely well and which re* malned about 8 miles south of the lakushioa lighthousa (30° 20' N, 130® 30 » EJ providing very good fishing. If we consider the season from the point of view of the various classes of boats which were fishing, the larger vessels gradually cans into operation from the early part of Llarch and were almost all fishing by the end of the mcxith. The majority of them continued to fish until the middle of Novei^er and a few operated until the first part of December. The peak of the season was from the middle of April until early June during which period more than two- thirds of the year's catch was taken. Four of the larger vessels fished in the Sanriku Area C Northeastern Japan2 from August to October, and their oatoh has been eliminated from the statistics. At the beginning of the season the smaller boats kept an eye on the activi- ties of the larger vessels and began to operate only after it had become clear that the season was under way in the Tokara Is. area [ 29® 37' N, 129® 43' E3 . Consequently their season began in the first part of April, was at its peak from April to June, and generally ended early in November. The peak season for the smaller boats in the southern part of the prefecture is during the period when the schools migrate into the northern part of the Shichit5, the eastern part of the 5sumi Kaikyo, and the waters adjacent to the Hyuga i^ada. The boata from the northern part of the prefecture - Kadogawa, Taina [ ? ^^ J& ) , Todoro, Shimanoura » operate in the same waters as those from "^he southern part of the prefecture during the early part of the season^ but from July to September meet of their fish off their home ports or in the waters west of Ashisurimisaki in Shikoku. (Table 1) (b) Skipjack catch The Ifiiidlngs for th*3 m-.ln parts of Irlyascki and Kugoshlma prefecturee for 194.7 are oho«n ic. Tables 2 ana 3. The figures on the Miyazakl PrefecturG landings aro thou,'»ht to be fairly compls'-iG, but In tha case of Kagoahlma Prefecture the landings for KogoshlTiia City, which ie tha siiln port for landing skipjack in the profectare, were not obtals^ed -ad ctha? Tendings not included in the statistics are thought to hB,ve reached a co.is Id arable amo'^t. Therefore it Is thought that the actual landings for that prefectur? wore oT'^r three tines the figure given in this report, (c) Fish catch statistics Tfebles /; and 5 show past ship jack catchos and the monthly catches for 1947 froB figures supplied by the statl^stlcal dopartraonts of the prefectural governments of Miyazakl and Kagoshlaa. (d) Ueasureinents of skipjack i, Slae compositlcn. The bIzo composition of the sample of 317 fish measured during this year is shorm in Table 6. By comparison with the catches mad® in areas other than the Satsunan Area, the proportion of larg»-sl»ed fish is very great, Tlie values also differ froo those obtained in past inves titrations re reported by Kimura ^ '. It Is not clear whether this is due to the email number of measux^menta which we made or whether it reflects a phenomenon peculiar to this year. 11. Table 7 shows the sex ratio and data on the length variation between the sexes for the 317 specimens. ill. Goiad weights and egg counts are shown in Table S. Further work is be- ing done at present on this aspect of the investigation. (e) Food habits study The small amount of data which we ccllected on the contents of the digestiro tracts of skipjack is shown in Table 9. (f) The period at which juvenile fish appear and thoir ecology Observations of the fish landed at the Aburatsu fish market showed that the catch from the waters adjacent to Takarajlma[29® 9' N, 129® 13' E J and Gajashima [ 29<* 54' N, 129<* 33* Ej from early October to the middle of November contains a good many individuals having a total length of 26 - 43 cm (weight 240 - 1,335 gr). labe had an opportunity to observe the ecology of small skipjack from a fishing boat in the Tokara group and at Torishlma between September 25 and October 4, and en this cruise about 300 small fish measuring 26-43 cm in total length were taken at several different fishing grounds in the vicinity of Qajanishlsone and Takarajlma. (Table 10), When these small skip- jack are cau^t no medium or large skipjack are taken along with them, the ' Kimura, Klnosuke. Dissertations on the Situation in the Fisheries for Inmortant Japanese Species C Nalchl Juyo Gyorul Gyokyg Ron J, First Edition, 1941 , p. 9. oaly mixad catch bolng a certain nufobar of dolphin, Goryphaena hippumg . i;o-60 CD long. From this fact it is thought that there small fish do not mingle with the schools of large fish but school separately, "n-.la year's experience indicates that thees small skipjack are more numerous on shoals comparatively close to islands, but nothing definite can as y^t be sa5.d on this point. (Persons who carried on the inveptigation =• I^lroshi Yabe, Tokumi Mori, and Yoehio Kizrowaki) 8 o S I o u to 00 a s a 1 * CB H 1 33 • • c J ^ o s o H « 2 u »4 cS t s (8 s «4 o 1 > H »4 O ■« 1 ^ • a t e 11 t-» s g a IS So s ^-ci a 4-1 C M 3 t>0 o at 5°.« •H •3 ss-sl 1 ^ sd H ° 1 -S s 1 '^ 1 1 *^ o 4* 35 IS u S ^^ 1 l„ • a § s M 2 tlO ^1 Si *> 1 n (S m vi Z o o o I— i o bD f*" ^ 1 a n a a E 2 a •p I O I n •P a J8 & a a o •P o wr\ I a o s I ^4 a e. •a o a. •H • o a c a a. a s '.I O la •H O o a :3 ^:g t; d •H O a "O Fi a o c So a 00 o a ® CM § rN i 5 S I a I I CO o 5 a o e 5 IS W M H Table 2 Landings l^ ten- day periods in Miyazaki Prefecture for 194.7 (in „._ -• a) Date January February March April May June July Auguat September October November DecGtnber Totals Place first 10 days second 10 days third 10 days first 10 days second 10 dsys third 10 ciaje first 10 dajs second 10 days third 10 driys first 10 days second 10 days third 10 days first IC days second 10 days third 10 days first 10 days second 10 days third 10 days first 10 days second 10 days third 10 days first 10 days second 10 days third 10 days first 10 days second 10 days third 10 days first 10 days second 10 days third 10 days first 10 deyrs second 10 days tMrd 10 days first 10 days second 10 days third 10 days units of kan) Kukushijne Kanaya Sotonoura Sekamatsu Melzu 628 2,633 965 1,^87 2,a8 ^2 281 9A(> 183 681 628 330 222 965 1,170 831 88 120 77 2,421 15,112 5,289 13,993 8,706 8,736 9,227 3,^0 2,157 2,009 1,733 2,811 1,840 163 3,0^5 181 672 10,225 11,322 3,803 81,580 336 3 15 168 30,622 831 7,524 13,112 6,366 U,962 15,232 20,202 8,849 2,379 2,484 1,379 2,298 0 0 1,165 223 UO 2,U0 90 99,346 ?Iatest 1. These figures are baaed on the reports of the local fisheries associations. 2. Landings of fish taken ivhlle operating In the Sanrlku Area have been omitted. 10 Table 2 (continued) Place Date first 10 days Januar7 second 10 days third 10 days first 10 days February second 10 days third 10 days first 10 days March second 10 days third 10 days first 10 days April second 10 dayo tMrd 10 days first 10 days May second 10 day a third 10 days first 10 days June second 10 days third 10 days firPt 10 days July sacond 10 days third 10 days first 10 days August sscond 10 days third 10 days first 10 days September second 10 days third 10 days first 10 days October second 10 days third 10 days first 10 days NoTerabel' second 10 days third 10 days first 10 days December second 10 days third 10 days Oaidozu Monthly Aburatau Kadog^Da Todoro Shimanoura Totals 6,850 15,620 27,563 a, 6^9 37,154 37,310 9.084 4,735 3,386 1,350 3,558 3,584 976 0 0 2,489 432 980 303 0 540 720 6,311 5,411 4,116 31,753 155,893 39,369 31,410 751 158 34 45,106 7,920 121 257 352,767 58,572 11,879 5U 392 58,474 1,769 542 11,388 2,404 191,765 11,489 1,539 22,033 0 17,594 1,954 83,705 14,347 2,527 10 1,934 9,348 1,084 2,247 0 25,632 4,417 7 1,983 378 524 716 179 0 18,362 5,130 305 136 2,952 a 2,828 13,453 6,072 6,116 476 0 379 7,819 547 Totals 197,563 394,U6 30,743 1,739 4,910 856,074 Notos: 1. These figures are based on the reports of the local fisheries associations. 2. Landings of fish tcUcen while operating in the Sanriku Area have been oaitted. 11 TaDJle 3 Sklpj*ick Lanilngs by Tai Day Piirlois At the Major Fishing Ports of Sngosh.lma Tre^'acture in 19^7 (in units of Ifan) Place Period January first second third MakXiTazald. Fobruar;^ FnhruaXT first second thiif. March first second third 2/>2 1,022 April first second third 7,023 3^,731 19,499 Hay first sec<»nd third 9,094 1,772 10,910 June first second third 5,060 3,U2 3,%1 July first second third 1,350 1,717 4,150 August first second third 1,402 739 409 September first second third 1,C67 B2 2,031 October first second third 3,098 1.115 309 November first second third 623 509 212 December first second third 12 18 39 Yamagawa Bo Anchorage Monthly Totals Totals 96,093 \ } )>■'• 4,6S3 70,607 72,900 25,503 \ 23, 723 U,1S1 \ U, 596 276,158 ) 508 \ 16, 995 32,999 635 6,997 2,941 > 3,122 } ■■ ) 523 530 81,812 6,U0 128,755 127,675 54,787 41.355 38,320 20,302 22,740 13,090 599 454,063 1. These figures are from the statistics on the fish handled by the various local fisheries associations. 2. 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