The albacore were in the cooler cyclonic eddies ; 

 the skipjack in the warmer anticyclonic eddies 

 along the front and the blue fin in the cooler 

 coastal waters. 



In exploratory longline fishing (35°- 

 45° N. , 160° E. - 160° W. , May-October), alba- 

 core were found between 15° - 21° C. with the 

 peak catches centered around 175 ° W. The north - 

 south and east-west distribution of albacore in 

 the region north of the subtropical convergence 

 (30° - 38° N. ) was also investigated. In an east- 

 west direction the peak catches were centered 

 between 170° E. and 180°, decreasing sharply to 

 the east and less sharply to the west. The peak 

 catches were recorded during midwinter . As to 

 the north-south distribution, the peak catches in 

 the fall and winter centered about 38 ° N., moving 

 to about 30° N. in March. The secondary peak 

 in latitudes 30° - 20° N. , west of 140° W. sug- 

 gests to the author migration along the sub- 

 tropical convergence. 



In the western half of the Pacific, yellow- 

 fintuna are caught along the Equatorial Counter- 

 current and are associated with areas of high 

 productivity, which are in turn related to a series 

 of eddies, i.e. eddies localized at about 135° - 

 145° E. , 155° - 165° E. , 175° E. - 175° W. , and 

 155° - 157° W. 



In the eastern equatorial Pacific, the 

 rich yellowfin areas are associated with the 

 regions of shallow thermoclines. The equato - 

 rial convergence at latitudes 1° to 3°N. may 

 also concentrate yellowfin either through the 

 concentration of food or through a barrier 

 effect. 



It i s proposed that secular changes in 

 oceanographic and fishery conditions are related 

 to climatological changes and the relationships 

 should be more fully studied. 



Watson, Margaret E. , and Frank J. Mather III 



Species identification of juvenile tunas 

 (genus Thunnus) from the Straits of 

 Messina, northwestern Atlantic, and 

 the Gulf of Mexico. /Conference Paper 

 VII - 137 



Two vertebral characteristics visible in 

 soft X-rays of juvenile fish as well as in hard 

 X-rays of adult fish provide the first positive 

 identification of juvenile bluefin tuna(T. 

 thynnus ), yellowfin tuna(T. albacares), blackfin 

 tuna (T. atlanticus ), and albacore (T. alalunga). 

 Blackfin tuna are separable from the other spe- 



cies by having 19precaudal and 20 caudal verte- 

 brae, a count which contradicts the work of 

 de Sylva (1955). U The other s p e c i e s having 

 identical vertebral counts,18 +21, are separable 

 one from each other on the basis of the position 

 of the first ventrally directed parapophyses. For 

 the yellowfin, this structure appears on the 

 seventh precaudal, for the albacore on the ninth, 

 for the bigeye and bluefin tuna on the eighth. A 

 juvenile bigeye (T. obesus) has as yet not been 

 X-rayed. It is presumed that the possible key 

 characters for separating a juvenile bluefin from 

 a juvenile bigeye would involve those also appli- 

 cable to the adults, the measurement of the orbit 

 diameter and depth, as well as comparing the 

 contour of the lateral line characteristic of each 

 species. 



Yabe, Hiroshi, and Shoji Ueyanagi 



Contributions to the study of the early 

 life history of the tunas. /"Conference 

 Paper VII - 67 



Larval net tows, dip netting, and survey 

 of stomach contents of adult fishes since 1949 

 by the Nankai Regional Fisheries Research 

 Laboratory have resulted in collection of approx - 

 innately 2,000 tuna larvae, 1,000 istiophorid 

 larvae, and considerable numbers of juveniles 

 of these fishes. The areas covered include a 

 great portion of the Indian and Pacific Oceans. 

 Larvae were taken in 1.4 or 2.0 m. nets hauled 

 horizontally, either at the surface or at three 

 levels, the deepest at 40-50 m. 



Larvae of Katsuwonus pelamis, Auxis 

 tapeinosoma, Neothunnus macropterus, and 

 Thunnus orientalis are described. In addition, 

 two types, A and B, suspected to belong to alba- 

 core and bigeye, respectively, are recognized 

 through their geographical and seasonal occur- 

 rence. These types are thought to be quite 

 similar to Neothunnus larvae with respect to the 

 absence of pigmentation on the trunk and late 

 appearance of chromatophores over the fore- 

 brain. Type A is characterized by the presence 

 of pigment on the tip of the upper jaw in speci- 

 mens about 8 mm. in fork length and the absence , 

 or only very faint presence, of pigment on the 

 tip of the lower jaw. Type B is mainly charac- 

 terized by pigment on the tip of the upper jaw at 

 5.3 mm. and on the tip of the lower jaw at 

 7. mm. in fork length. 



7/ de Sylva, Donald P. 1955. The osteology 

 and phylogenetic relationships of the blackfin 

 tuna, Thunnus atlanticus (Lesson). Bulletin of 

 Marine Science for the Gulf and Caribbean, 

 Vol. 5, No. 1, p. 1-41. 



40 



