(8) On the migrations of the skipjack schools 



The following is an outline of the ideas of Technician Uda 

 of the Central Fisheries Esperimcnt Station concerning the 

 migrations of the skipjack as revealed by the shifts in the 

 month of greatest catch (see the following table ) in the waters 

 extending from the Satsunan Sea Area to the Northeastern Sea 

 Area, 



ao Schools of small skipjack (under h pounds in weight) 

 The main group starts out from the Satsunan Sea Area 

 in May J, passes through the waters off southern Japan, 

 and arrives in the Zunan Sea Area chiefly in June 

 and Julyo Ihese fish advance into the Northeastern 

 Sea Area in August and September o There is in addi= 

 tion a second grotp of small skipjack which starts 

 out from the Zunan Sea Area at about t he same time 

 that the other group originates in the Satsunan Sea 

 Areao This latter groi^j .arrives in the Northeastern 

 Sea Area in May and Juneo 



bo Schools of medium=sised skipjack (weight from I4 to 8 

 pounds ) 



Ihere is a main group which originates in the Satsunan 

 region in Marchj, shifting the center of its groiqj of 

 schools to the Nankaid© Sea Area in Aprilj, and to the 

 Zunan and Northeaster-n Sea Areas around Julyo There 

 is thought to be a vaguely define^ second group of 

 medium=sized skipjack which originates in the Zunan 

 Sea Area in April and reaches the Northeastern Sea 

 Area in Mayo It £5)pears that the catch of mediura= 

 sized skipjack in the Satsunan Sea Area around 

 September is due tj a return cf part of this latter 

 group to the southwesto 



Co Schools of large skipjack (weight over 8 pounds) 



These schools appear centered in the Satsunan Sea Area 

 in May^ and thereafter move northy appearing in the 

 Zunan Sea Area in July and in the Northeastern Sea 

 Area in July and Augusto (A part of this group remains 

 in the Satsunan Sea Areaj, and the peak catch in that 

 area is also in Julyo) A second peak in the catch in 

 the Zunan Sea Area in May indicates that there is a 

 second source of large ^pjack in that sea areao 

 (Of course J, there must be many small skipjack ihich 

 become medium skipjack and medium skipjack which 

 become large skipjack by growth during the course of 

 the migrationo This should particularly be taken into 

 account in sea areas where there is an abundant sipply 

 of natural food)o 



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