and driving them into a tight mass irtiile greedily feedine around the 

 edgeSo Skipjack schools sometimes accompany kambeizame £ a species of 

 shark_/ and Sferdine mhaleSo 



(3) The large skipjack stage (over 1^000 momme £8,28 lbs„_7 weight, 6 to 

 8 years old) 



In this stage of development the body depth increases greatly in 

 relation to the lengthy the fish becomes stouter, and its movements become 

 slower. Its food consists of squid, crustaceans, and miscellaneous fish. 

 The fish generally move to the reefs of outlying islands and become 

 deficient in schooling instinct with a tendency to remain in small groups 

 at "fish nests^o Until they attain a weight of about 2,000 momme (_ 16,56 

 lbSo_7 they retain some of their migratory tendencies, but old fish over 

 that weight do not migrate and remain all the year round permanently 

 resident at the fish reefs of the low latitudes^ Or they may wander 

 around the open sea together with the albacore and come to live in waters 

 as cold as IS'-'Co They have a strong tendency to become what is commonly 

 called dekiuwo / "adventitious fish"_7 and generally keep to the lower 

 depthSc rising to hunt food only at certain tides or in the dim light of 

 morning and evening „ 



Note s Dekiuwo are fish which are attracted to the surface by chum-bait 

 or trolling lures. 



Paragraph 2 Migrations 



It is instinctive with the skipjack schools of the southern seas to 

 migrate regularly into Japanese waters in the spring and summer of each 

 yearo That iSj while instinctively migrating in search of food they 

 enter the waters adjacent to Japan, but viewed objectively the migration 

 is controlled by the currents in the waters vriiich the fish inhabito As 

 shown in Fig, 3^ the Northern Equatorial Current runs from east to west 

 the year round in the vicinity of 5 = 10° north latitude^ In the waters 

 adjacent to "ie Philippines it changes from a westerly to a northerly 

 current^ flo-/3 along the east coast of Taiwan, continues north along the 

 Okinaws chain, ^and impinges upon the coasts of Japan beginning with 

 southern KyushUo From the middle of March, when the Kuroshio is at its 

 height, a part of the fish which live within the Equatorial Current 

 fcllc'.7 it and are naturally brought into the adjacent waters of Japan, 



If we were to classify skipjack schools from the point of view of 

 their migrations, it is assumed that the classification would be as 

 ■^ollowss 



(a) Schools which spend their whole lives in the tropical seas south of 

 23° north latitude, 



(b) Schools which make a great circular migration in the northern Equatorial 

 Current when it is at its height in the spring and summer, 



(c) Schools which r.ove north and south in the Kuroshio, 



19 



