With regard to the tagging of tvma, Teclinician Yokoyama of this Station 

 has devised the method of using a regvilar trolling line rigged so that when 

 a fish strikes the tag, the hook and a part of the leader will break off. 



Table 8 shows the results of the tagging of small tuna from the set 

 nets of Yoichi and Furuhira in August and September 1933, by Assistant 

 Technician Nakashima of this Station, using tags attached to the caudal 

 pedunclso 



From these facts it appears that although the fish make small localized 

 migrations in search of food during the summer season, they move southward 

 with the falling water temperatures in the autumn. It should be borne in 

 mind, however, in this example that the fish were released at just about 

 the northern limit of their area of migration „ 



Since taggings of small tuna are scheduled for the Pacific Coast in 

 the future it is to be expected that migrations of this sort will gradually 

 become clarified. However, in the present paper we will expound our 

 hypothesis concerning the migrations of the tuna in the Pacific coastal 

 waters of Hokkaido based on obser^/ation of the shifts in the fishing 

 seasons and the fishing groundso 



The place in Hokkaido where the earliest catches of tuna are made is 

 in the set nets of Kayabe-gun, following the northern part of Aomori 

 Prefecture, Therefore these schools must be fish which have been drawn 

 from the Iwate area by the Tsugaru Current and have moved north through the 

 waters off Shiriyasakio The theory is also held that they migrate from 

 the Japan Sea through the Tsugaru Strait, but the truth or falsity of this 

 waits upon future investigations^ Next the Kushiro and Urakawa drift- 

 net boats make their first catches in the latter part of June from 33 

 miles south of Erimosaki to off Hitaka. These schools, through the third 

 branch of the warm current described in a later section, move north 

 farther off shore than the previously mentioned fish. In some years 

 these schools move on from the Kushiro area north to the Etorofu area. 

 Part of them must turn left from the coastal waters of Hitaka to enter 

 Funkawano Furthermore, some of the fish off Kushiro move north along 

 the second branch of the warm current. The above are the deduced migra- 

 tions of the so-called ascending tuna, east of Erimosaki the large tuna 

 migrating comparatively close to the coast while the small fish are 

 farther off shore. From the latter part of September to October the 

 fish gradually begin to move south. Their route follows the outer edge 

 of the coastal stream of the Chishima cold current to the waters off 

 Erimosaki, from where some of the fish head for the Funkawan and Shiri- 

 yasaki areas while others head for the Kamaishi area. There appear to 

 be some fish which move southward off shore with the retreat of the 

 second branch of the warm current off Kushiro, The above is what may 

 be called the grand migration, however, along the route at Shiriyasaki, 

 Erimosaki, and off Kushiro there are localized migrations covering 

 considerable periods of time. These are food-seeking migrations which 



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