Notes Most of the albacore landed at Misaki are U, 5s. and 



6-7ear-old fish. The U and 5-year-old fish fall within 

 the "small" category as defined above, but the 6-year- 

 old fish are medium-sized albacore. 



III. Some thoughts on the migrations of the albacore 



Taking into account differences in the relationships between fishing 

 groxuids and oceans currents and seasonal and regional differences in the 

 water temperatxire and salinity of the fishing grounds, and the size of 

 the fish, and utilizing data gathered by the fisheries experiment stations 

 of various regions, Technician Uda of the National Fisheries Experiment 

 Station has put forth the following working hypothesis with regard to the 

 migrations of the albacoreo It is recorded here in rough outline to 

 serve as a reference for future investigators o 



(1) Schools may pass back and forth between the coastal population 

 and the offshore population, but at present it is most reasonable 

 to consider these as two separate stocks. 



(2) The coastal population consists of its own peculiar stock (medium 

 and small albacore) and schools (small and medium fish) which enter 

 it from the offshore waters, 



(3) The offshore population consists of its own peculiar stock (large, 

 medium, and small fish), and of schools, mainly medium-sized fish 

 (including a certain number of small fish), which enter it from 

 the coastal waters. 



The numbers in which these albacore migrate affect the success of 

 the fishery for the year, 



(k) Recently the stock peculiar to the coastal waters and the amount 



of fish entering this stock from elsewhere have declined in numbers, 



(5) The stock peculiar to the offshore waters and the recruitment 



into that stock from the coastal waters may be decreasing, however, 

 there are no signs of a decrease as marked as that which has taken 

 place in the coastal areas. 



This is the hypothesis offered at present, however, these problems 

 will be greatly clarified, it is believed, by tagging experiments, 

 physiological investigation of spawning, investigation of the summer 

 habitat of the fish, and a study of the catch statistics from the 

 point of view of age composition, (Ifechnician "fekeo Sasaki). 



15 



