From ths 1935 investigations it appears that the skipjack 

 schools of the Hokkai-Saririku Sea Area have characteristics 

 differing from those of the southern sea areas as regards the 

 size of the fish and the objects '^Tith -vshich they are associated, 

 and further that tiie water temperatiires suitable for catching 

 them are markedly lc"A'Qr than in the soiit.h and have comparatively 

 limited values (22-23^ C)-^, all of which seems to mark it off 

 as an area in which the schools are clearly of a different 

 conposition, however, it is thougnt that the schools themselves 

 come from the Zunan Sea Area and the areas to the south and 

 west (including Satsunan) in the spring and shimmer and return 

 sou "Hi in the fallo 



Finally I vdsh to "thank Dr., Morisaburo Tauchi, professor 

 in the Fisheries Institute, for his valuable i;-istruction con- 

 cerning the theory of skipjack migrations presented in this 

 paper, and Technician Itax-o Takayama of the Imperial Fisheries 

 Experiment Station for malcing tlie data availableo 



Summary 



(1) According to tiie investigations of 1933» the majority 

 of the skipjack schools fished in the Hokkai-Sanriku Sea Area 

 are medium-sized skipjack^ while in ths southern sea areas 

 schools of large and small fish make up a comparatively 

 important part of tlie catcho The proportion of medium skip- 

 jack to large and small fish is least in the southern areas 



at the same period (May, June, Jioly) when it is greatest in the 

 Hokkai-Sanriku Sea Area,, 



(2) Investigating the month of highest catch in each sea 

 area by large, medium, and small sizes, the migrations of the 

 skipjack schools were discussed separately by sizes o Groups 

 of skipjack schools which migrate from south to north in the 

 spring and summer and retreat southward again j.n the fall were 

 hypothesized and it was thought that they must be con??Gsed of 

 schools of at least two strains, one originating in the Satsunan 

 area and one in the Z'jnan areao Fui'ther, it is thought that 

 there are probably only migratory schools, with no pennanently 

 resident schools, in the Hokkai-Sanriku Sea Area, but for the 

 Ziman and Satsunan sea areas we must believe that there are, in 

 addition to the north-south migrating schools, other local 

 schools which make small localized migrations. 



1/ 



T3.kayama, Ikeda, and Ando: A study of tiie skipjack fishing 

 si-^-uation in 1930.. Jcuro Imp. Fich„ Zxpto Sta. No, 5s 193i;i 

 33-31;. 



66 



