The first of these, the long-finned tuna, is rarely found in the Japan 
Sea, hut is widely distributed in the Pacific. It migrates northward 
in spring, reaching the northeastern shores of Japan in summer where 
it is caught with bonito. Yellow tuna is widely distributed along the 
Pacific coast from Hokkaido south to Formosa, but is rarely caught in the 
Japan Sea. It migrates to the northeast coast of Japan in summer, approach¬ 
ing fairly close to shore. Black tuna has wide distribution from the 
Kuriles to the South Seas and unlike the other species is caught in fair 
amounts in the Japan Sea. South of Kyushu it is found all year round 
but along the coast of Honshu moves north in early summer and returns 
south in late autumn. Mebachi has a distribution from about the northern 
boundary of Chiba Prefecture to waters south of Formosa on the Pacific 
side, and is not found in the Japan Sea. 
Ihe peak season for tuna in the coastal waters is the summer 
although some species, for example the black tuna on the Pacific side, 
are taken in winter, 
Sugiura 16/ divides the deep sea tuna grounds into the following 
six districts of which the first three accounted for more than 90 percent 
of the catch: 
1. Hokkaido and northeast Honshu 
2. The Isu district, extending south from the Izu Peninsula 
3. The Nankaido district extending from Shizuoka Prefecture 
southweatward toward Shikoku 
4. From south Sat soma southward 
16 / Sugiura, Y. Suisan , 1939. 
• 38 - 
10-031 P 60 t)tl 
