From the Bulletin of the Japanese Society of Scientific 

 Fisheries, Volo 11^ No, 5-6^ ppo 179-l83o March 19k3, 



On the Stock of Skipjack 



by 



Morisaburo Tauchi 



(Fisheries Institute) 



From the results obtained by Uda and TsukushiVin studying 

 by mcHith and by area the composition of the catch in terms of 

 large, medium, and small fish, it can be thought that the skip- 

 jack that are taken in the waters adjacent to Japan migrate 

 from south to north through the spring a^id summer and retreat 

 southward in the autumn^ that they consist of tiro strains^, one 

 originating in the Satsunan area and one in the Zunan area? and 

 that in the Hokkaido-Sanriku Sea Area there are probably only 

 migrating schools^, with no permanently resident schoolSj, while 

 in the Zunan and Satsunan sea areas there are^, besides these 

 north-south migrating schools^ sedentary local schools which 

 make only small migrations o Okamoto§/j studying the body- 

 weight composition of tiie catch by months and areas ^ inferred 

 that in the areas of the Satsunan and Ogasawara islands the 

 schools composed chiefly of young fish under 2o9 pounds or of 

 mature fish over i;o6 pounds remain as sedentary fish 9 and that 

 the medium sized fish of 2o9 to keS poundsj, which can be 

 regarded as being of roioghly the same age group (fourth-year 

 fish) J are those that around May and June come from somewhere 

 and appear densely congregated off ShikokUj, in the Kimiano Nadaj, 

 and off Zunan, and then from July to October move into the 

 Northeastern Sea Areao AikawaJ/j, studying the condition factor 

 of skipjack schools j found that in the RyukyS Sea Area the 

 schools with a condition factoi under 20 remain in the vicinity 

 of islands and shoals j while the schools with a condition factor 



i/ Udaj Michitaka and Jiro Tsukushis Local Variations in the 

 Composition of Skipjack Schools,, Bullo Jap., Soc. Sci Fish 

 3 (h), 193ko 



2/ OkamotOj Gorozos On the Weight Composition of the Skipjack 

 Schools of the Northeastern Sea Areao Bullo Japo SoCo Scio 

 Fish 9 (3jj I9UO0 (Translated in FWS Special Scientific 

 Report Fisheries Noo $1 - Japanese Skipjack Studies) „ 



2' Aikawa, Hiroakis A Study of the Skipjack Schoolso Bullo 

 Japo Soco Scio Pisho 6 (l)j 1937o 



22 



