118 



FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



Table 4. — Measurevienls of four bluefin tuna from the western 

 equatorial Pacific 



I DeQned as the distance from a line connecting the insertions of the ventral 

 fins to the anterior edge of the vent. 



records of this species from the southern Philip- 

 pine Ishmds as cited by Wade (1950b). How- 

 ever, Wade believed that the southern distribution 

 of T. orientalis was limited to the northern Philip- 

 pine Islands and that other records were of stray 

 fish. 



The bluefin tuna herein recorded have been 

 assigned to T. (m-entalis on the basis of distribu- 

 tion alone. It may be shown in the future that T. 

 orientalis is either a valid species or is synonymous 

 with T. thynnus. 



SUMMARY 



Various biological investigations were con- 

 ducted aboard a Japanese tuna mothership on 

 tunas and other fishes landed by longline-fishing 

 vessels which operated in waters south of the Caro- 

 line I.slands during the summer of 1950. The re- 

 sults of these studies shed new light on the spawn- 

 ing and distribution of tuna species found in the 

 western equatorial Pacific. 



Gonads of yellowfin tuna and big-eyed tuna were 

 examined for sexual maturity, and their condition 

 suggests the existence of spawning grounds for 

 these two species in or near the region fished. The 

 yellowfin probably spawns most actively during 

 the summer months. Observations of big-eyed 

 tuna lead to the conclusion that this species spawns 



from June to September, and possibly during other 

 seasons of the year. 



Several juvenile oceanic skipjack were recovered 

 from the stomachs of tunas and other pelagic 

 fishes. This is definite proof that oceanic skip- 

 jack spawn extensively in or near the area covered 

 by the expedition. 



The occurrence of bluefin tuna in equatorial 

 waters is recorded on the basis of several fish 

 caught from June to September 1950. 



LITERATURE CITED 



Abe, Tokihaku. 



1939. A list of the fishes of the Palao Islands. Palao 

 Trop. Biol. Sta. Studies, No. 4, pp. 523-583. 

 GoDsiL, Harey C, and Robeet D. Byebs. 



1944. A systematic study of the Pacific tunas. Califor- 

 nia Div. Fish and Game, Fish Bull. 60, 131 pp., 18 

 tables, 76 flgs. 

 Hatai, Shinkishi, et aL 



1941. A s.vmposium on the investigation of tuna and 

 skip.iack spawning grounds. South Sea Science 

 [Kagaliu Nanyo], vol. 4, No. 1, pp. 64^-75. 



HoLI.ISTER, GlOKIA. 



1934. Clearing and dyeing fish for bone study. Zoo- 

 logica, vol. 12, No. 10, pp. 89-101, figs. 18-21. 



INANAMI, YOSHrrCTKI. 



1942. Small skipjacli captured at Truk. South Sea 

 Fish. News [Nanyo Suisan Joho], vol. 6, No. 1, 

 p. 524. 



KiSHINOUYE, KaMAKICHI. 



1923. Contributions to the comparative study of the so- 

 called scombroid fishes. Jour. Coll. Agrie. Imp. Univ., 

 Tokyo, vol. 8, No. 3, pp. 293-475, 26 figs., 22 pis. 



1924. Observations on the skipjack fishing grounds. 

 Proc. Sei. Fish. Assn. [Suisan Gakkai Ho], vol. 4, 

 No. 2, ijp. 87-92. 



LiSSNEE, H. 



1934. On races of herring. Jour, du Couseil, vol. 9, 

 No. 3, pp. 346-364, 2 tables. 

 Mare, John ('., and Mit.Nint B. ScHAEFiat. 



1949. Definitions of body dimensions used in describ- 

 ing tniias. U. S. Fish and Wildlife Service, Fishery 

 Bulletin 47, vol. 51, pp. 241-244, 1 flg. 

 SoHAEFKii, Milker B. 



193(i. Contribution to the life history of the surf smelt, 

 Hyjioiiiesiis pretiosus, in Puget Sound. Washington 

 State Dept. Fish. Biol. Kept. 35B, 45 pp., 17 tables, 

 33 figs. 

 Schaefee. Milnee B., and John C. Mabb. 



1948a. Contributions to the biology of the Pacific tunas. 

 U. S. Fish and Wildlife Service, Fishery Bulletin 44, 

 vol. 51, pp. 187-206. 5 tigs. 



1948b. Juvenile Euthynnus Ihicatiis and Aiixis thazard 

 from the Pacific Ocean off Central America. Pacific 

 Science, vol. 2, No. 4, pp. 262-271, 4 flgs. 



