No east-west differences in occurrence of devel- 

 oping ovaries were discernible. 



Otsu, Tamio, and Richard N. Uchida 



A model of the migration of albacore in 

 the North Pacific Ocean. /Conference 

 Paper II - \J 



On the basis of tag recovery data, age 

 and growth information, and distribution and 

 size frequency data from the various fisheries, 

 a model of the migration of albacore in the North 

 Pacific Ocean has been developed. This model 

 is consistent with the hypothesis that there is a 

 single population of albacore in the North Pacific 

 Ocean. 



The migration of albacore within the 

 areas of the three major fisheries is in general 

 reflected by the seasonal shifting of the respec- 

 tive fishing grounds. The migration between 

 fisheries may be summarized briefly as follows : 

 A varying portion of the 2-, 3-, and 4-year-old 

 fish and nearly all of the older fish in the Amer- 

 ican fishery migrate westward each fall into the 

 Japanese longline fishery, and during the follow- 

 ing spring, into the Japanese live -bait fishery. 

 The remainder of the fish from the area ofthe 

 American fishery move westward to the mid- 

 ocean waters of the North Pacific, some as far 

 west as to the eastern fringe of the Japanese 

 longline fishing grounds. These fish, largely 

 young individuals, tend to return to the American 

 fishery the following summer. Thus, some alba- 

 core may be available to the American fishery 

 for as many as four or five successive seasons. 



Of the more common sizes taken in the 

 Japanese live-bait fishery, only the 4- and 5- 

 year-old groups provide some fish that enter the 

 American fishery the following summer, but 

 these are few since 5- and 6-year-old fish com- 

 prise only a very small proportion in the Amer- 

 ican catch. This would explain why none ofthe 

 albacore tagged in the Japanese live -bait fishery 

 has thus far been retaken in the American fishery. 



Albacore enter the winter longline fish- 

 ery from both the American fishery and the 

 Japanese live-bait fishery. A large part of these 

 fish migrate southwestward in the winter long- 

 line fishery and subsequently enter the live-bait 

 fishery in the spring, whereas a few separate 

 and migrate into the American fishery by sum- 

 mer. 



A portion of the large adults occurring 

 in the Japanese winter longline fishery (6-year- 

 olds and older) move southward during the spring 



into subtropical waters, where they makeup the 

 reproductive unit of the North Pacific population. 



It is hypothesized that spawning occurs 

 in subtropical waters during the summer and 

 that the larval and early juvenile stages are spent 

 in these waters. When about 1 year old, the 

 fish migrate into temperate waters, but they do 

 not immediately join the exploited stock. The 

 albacore are generally not available to the com- 

 mercial fisheries until they reach the age of 2 

 or 3. 



It appears that most of the recruitment 

 into the exploited stock takes place in the east- 

 ern rather than the western North Pacific. There 

 is a greater volume of migration of the commer - 

 cial sizes of albacore in the westerly direction 

 from the American fishery into the Japanese 

 fisheries than vice versa. 



Ridgway, George J. 



Distinction of tuna species by immuno- 

 chemical methods. /Conference 

 Paper III - 5] 



Through the application of the Ouchter- 

 lony method of diffusion precipitin analysis, with 

 rabbit immune sera, the presence of species 

 specific differences in serum antigens of adult 

 tuna was demonstrated. The existence of these 

 differences was confirmed by absorption 

 methods. 



In studies on soluble antigens of the 

 muscle tissue of tuna, evidence was obtained for 

 the distinction of skipjack from albacore, yel- 

 lowfin, and bigeye tuna. 



No characteristic differences in their 

 soluble tissue antigens, allowing the mutual dis- 

 tinction of the latter three species, were found. 

 Technical problems in the study of soluble tissue 

 antigens, involving extraction media, stability 

 of extracts, and production of potent antisera 

 were encountered, and preliminary methods for 

 their solution developed. 



The course was discussed whichfurther 

 developments in these and allied fields might 

 take resulting in possible distinction of larval 

 forms. 



Roedel, Phil M. , and John E. Fitch 



Taxonomy and nomenclature of the Pa- 

 cific tunas. /Conference Paper VI - Z] 



