of medium-sized albacore. The schools which moved southwest closest 

 to Japan represent the western extremity of the schools moving through 

 the North Pacific fishing ground as a whole, and this population has the 

 largest proportion of schools of small fish. It is thought that this group 

 appears in the Kinan Sea Area in March. Even within the Kinan Sea Area 

 the albacore which migrate closest to the coast of Japan, and are taken 

 in the areas west of the Izu Islands have an extremely high proportion of 

 schools of small fish. 



The length composition of the albacore landed from this sea area 

 in many cases coincides with or is extremely close to the size composi- 

 tion on the North Pacific fishing ground, although there are differences 

 from year to year in the length classes at which the modes appear. 



In the early part of the season, for a time, the central portion of 

 this sea area has fishing grounds which appear in isolation from the North 

 Pacific fishing ground, but these grounds suddenly extend and quickly be- 

 come continuous with the North Pacific fishing ground. The zone of high 

 catch rates expands from the east toward the west. Judging from this 

 pattern of movement of the fishing grounds, there is thought to be a very 

 high possibility that this population originates in the albacore distributed 

 in the area of 140°E. to 150°E. 



East and west of the line of the Izu, Ogasawara, and Mariajia 

 archipelagoes differences of various sorts can be found in the other tuna 

 and spearfish species. For example, the bigeye tuna which are taken 

 mixed with the albacore on the west side of the island chain reach a con- 

 siderable number, but on the east side the proportion decreases drastically. 

 In the case of albacore, too, the schools of large fish which appear around 

 Okinotorishima find no analogy on the east side of the island chain. Changes 

 from year to year in the catch rates appear to be in agreement as between 

 the Kinan fishing ground and the Okinotorishima fishing ground. (There is 

 a need for a further examination of this point when more data have been 

 assembled.) Consequently, there are a number of circumstances remaining 

 to be further examined with regard to whether or not the albacore of the Kinan 

 fishing ground and those of the North Pacific fishing ground can be considered 

 to be one population. 



An outstanding characteristic of this sea area is the great speed 

 with which the albacore fishing grounds are formed. It is thought that 

 this phenomenon may be based on the special characteristics of the oceano- 

 graphic conditions in this sea area. This phenomenon does not immediately 

 negate the connection with the area of 140 E. to 150 E. , but, on the other 

 hand, neither can it be explained by hypothesizing the independence of the 



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