TUNAS FROM WESTERN EQUATORIAL PACIFIC 



117 



been a juvenile skipjack, 

 ered for these specimens : 



The following data were gath- Table 3. 



-Bluefin tuna captured in the western equatorial 

 Pacific, June-September 1960 



Date of capture 



June 17. 

 June 26. 

 Julys,. 

 July 12. 

 July 14. 

 July 19. 

 July 26. 

 Aug. 10 

 Aug. 12 

 Sept. 4. 



Locality of capture 



Latitude 



4°20' N. 

 4''30' N. 

 2°39' N. 

 4''0»' N. 

 3°48' N. 

 5°02' N. 

 2''25' N. 

 4°00' N. 

 4n5' N. 

 2°2S' N. 



I/ODgitude 



145''ao' E. 

 145°10' E. 

 148'>40' E. 

 147''57' E. 

 147<'55' E. 

 154-16' E. 

 155<'49' E. 

 157''30' E. 

 Mift'W E. 

 155''49' E. 



(1) Dimensions: Length, 6.6 sun (198 mm.); weight 



2r. mo«(»ie (94 grams). Fish No 

 Date of capture : 1700, April 23, 1939. 



Place of capture : 4 nautical miles southwest of 



Sarasbinm Pass (Salat Pass, 7'14' N., 152''01' E.). i 



Method of capture : Pole fishing. 3"1!11II1III1I 



At the same time, a specimen which could have been * 



placed in a rice bowl and assumed to have been 6 



about 3 snn (90 mm.) in length was caught but not gllilllllllllll 



retained owing to the carelessness of a crew ';- 



member. 



(2) Dimensions: Length, 1.5 sun (4."i mm.); weight, 



2moinme (8 grams). .species was caucfht this year indicates a possible 



Date of capture: May 3, 1940. , • j- . ' • •., j- ^ -u x- 



n, - . , , »■ , •, ^. ,.. , • change in tactors {loveniinsr its distribution or 



Place of capture: 14 nautical miles oft Sarashima * . . . "^ g. 



Pagg availabihty in the western equatorial region. 



Method of capture : Recovered from the stomach of a Examination of available published logs covering 



skipjack which apiiarentiy had been caught im- the prewar activities of Japanese tuna-fishing ves- 



mediately after feeding, for there was no evidence gg]g j,^ ^^^ p^i.^^,^ Mariana, and Caroline Islands 



failed to show bluefin tuna in their catches. With 



It is said that small fish weighing 25 momme (94 grams) ^he exception of Abe's listing (1939) from the 



are extremely rare around Truk, but that fish of this size t> , t i i j n,n . -i ,-i? i 



„ ,, , n 1 1 • <-  c „* r^alau Islands oi a 240-mm. specimen identined 



are often seen around Palau during certain sea.sons of ^ ^ _ _ 



some years. ^^ Tfainmts thynnus{ = Thimmis onentcdis'i) , gis 



Altliough oceanic skipjack are known to be 

 abundant in the vicinity of the many islands and 

 reefs of the western equatorial region, this species 

 apparently is not landbound, for several schools 

 were seen and fished far from land during the 

 operations of the expedition. Spawning prob- 

 ably takes place in the open ocean, as well as near 

 land, as inferred from the recovery of juveniles in 

 fresh condition from fish caught in deep offshore 

 waters. Judging from the sizes of young slcip- 

 jack found, some spawning must occur during the 

 spring months. Kishinouye (1924) estimates that 

 young skipjack grow at a rate of more than 40 mm. 

 a month. Calculations based on this growth rate 

 suggest that juveniles recovered aboard the moth- 

 ership in Julj' were spawned in March and April, 

 and those found later, in April, May, and June. 



OCCURRENCE OF BLUEFIN TUNA 

 (THUNNUS ORIENTALIS) 



The bluefin tunas are generally regarded as 

 temperate-zone foi-ms and are seldom found in 

 tropical waters. The capture of 10 large tunas 

 identified as bluefin or black tuna, probably Thwn- 

 ?r(/.s- oHeiifalis (Temminck and Schlegel), l)y expe- 

 dition vessels is therefore of interest (table 3). 

 Furthermore, the frequency with which this 



far as is known, no other distribution i-ecords exist 

 for bluefin tuna from this general area. 



The captured fish were all large and weighed 

 from 150 to 500 pounds eviscerated and with gills 

 removed. Since these fish were cleaned at sea 

 immediately after capture and the viscera dis- 

 carded, it was not possible to examine the internal 

 organs and gill rakers. The pectoral fins of those 

 individuals examined were comparatively short, 

 and eacli fish was characterized by a dark over-all 

 coloration, which varied from black dorsally to 

 a dusky graj' veutrally. Measurements of dif- 

 ferent body characters, using standard morpho- 

 metric techniques described by Marr and Schaefer 

 (1949), were taken of four fish. The data are 

 presented in table 4. 



There are three commonly recognized bluefin 

 species inhabiting the Pacific Ocean: the south- 

 ern bluefin tuna of Australia, Thimrvus maccoyi; 

 the Japanese bluefin or black tuna. Thunnus or'i- 

 entalis; and the so-called California bluefin tuna, 

 Thviimis thi/niiii,s. which is found in the eastern 

 Pacific and adjacent waters. The presently recog- 

 nized northernmost limit of distribution of T. 

 maccoyi is Sydney, Australia (Serventy 1941). 

 The Japanese bluefin tuna, T. oriodaJis, which has 

 yet to be proved distinct from T. thynnus, may 

 occur as far south as the equator, for there are 



