The tuna which moTe north along the Pacific side pass 

 through the waters off Sanriku by summer and reach Hokkaido 

 and the Kurileso During this northward migration their route 

 lies very close to land and they are taken abundantly in trapsc 

 It is also said that they generally swim close to the surfaceo 

 They remain in the Hokkaido area until autumn^ and then with 

 the falling temperatures they turn southwardr. It is thought 

 that at this time they take a route farther offshore and swim 

 at somewhat greater depths o 



There are schools which are believed to make a migration 

 completely different from this^ These are the schools iflrtiich 

 appear in the Formosan and Philippines regions. The reasons 

 for thinking them a different population are their aforementioned 

 markedly greater size^, their having a markedly later season for 

 migrations and the difference in spawning season„ 



In the schools which appear in the waters adjacent to 

 Luzon and Formosa the fish are generally of large sizej, those 

 taken at the beginning of the season being almost all over 300 

 kgo As time passes they gradually become smaller in size^, but 

 even at the end of the season fish of less than 150 kgo are 

 extremely rare., However, according to Dro Kishinouye's 

 observations on the tuna taken in the vicinity of Tanegashima, 

 a fish as large as 150 kgo would be considered to be on the 

 big sidec The fishing season in the Luzon and Formosan waters 

 has in recent years gradually been becoming earlierc The fish 

 appear in the northern part of the South China Sea in the middle 

 of February in early years and ordinarily in the middle of 

 Marcho The schools suddenly become densely concentrated both 

 on bhe east and west in an area centered around the Bashi Strait, 

 and in April and May the fishing season is at its heighto In 

 other words 1 the season is more than two months later than in 

 the Tanegashima v/aters„ In June when fishing in the South 

 China Sea area is coming to an end, the fishing grounds shift 

 into the area of the Kuroshio^ Then there are no longer any 

 concentrated fishing grounds, but catches are made scattered 

 over a broad area, showing that the schools are moving northo 



The above two strains, considering the size of the fish 

 that compose them^, are thought to be clearly two different age 

 groupsc Since, however, it appears that the schools -viiich 

 appear in the south also move north along the Kuroshio, it 

 would be hard to say definitely that there are no fish from 

 the south among the large tuna that are taken in the Hokkaido" 

 area in the summer and fallo , Up to now the relationship 

 betiveen these tw'^o strains has been completely unknownc This 

 is particularly the case now that there is no method of making 

 a comparison, since in recent years it has got so that the 

 schools do not appear in the vicinity of Tanegashima at alio 



