マグロ・カジキ類の胃内容物中にみられるカツオ若年魚

抄録

From the result of the researches for the stomach contents of the tunas and marlins, which have been carried out from March 1949, considerable number ofthe juveniles of tunas, marlins and swordfish are found. Of these juveniles, skipjacks of the length 70-450mm are the most abundant ones. On the bases of these juvenile skipjasks, the following ithems are treated.
i) Seasonal and local appearance.
ii) Local size-compositions and their seasonal variations.
iii) Description of the characters on these specimens which are not much digested.
Within the limit of the investigations, which were taken place in the adjacent seas of the South Sea Islands, the Bonin and the Midway island, these juveniles appear without distinction of the seasons and the localities. The abundance and the size-composition of these juveniles, seem to differ remarkably according to the differences of the seasons and the localities. Such differences are considered by the author, to have close relation to the subtropical convergence. Furthrmore, cosidering from size-composition and locality of their appearance, the author hypothesizes that the skipjack spawns in the vast areas of the tropical and subtropical seas, not by any means in a short period.