hlBtoxy of thle migratory spcoles; maeb IntnnBlTe reeeaxcb 1b needed before It can be aatls- 

 faetorllj' understood. 



Japaneee Stock; During Becem'her and January, the black tuna la found In the sea 

 region directly south of Kyushu (Figure 8). From Fobniary through April, as the warm Kuro- 

 shlo Current extends Its Influence northward, the schools begin migrating along the eastern 

 coast of Kyushu and Shlkoku. Klmura (unpublished data) has evidence that, in this region, 

 the shoals begin to separate Into two groups. One continues northward along the Honshu 

 coast while the other moves southward to the areas around the Bonln, Calto, and Byukyu is- 

 lands. 



The shoals moving northward appear off the Shlzuoka and Chiba prefectural coasts 

 (east central Honshu) during April and May and generally reach the Toholni region during the 

 late spring and summer months (Kay through July). Many of the females taken In the Tohoku 

 area are spent. Kishinouye (1923, p 441) believed that they spawned in the offshore waters 

 east of Honshu 'cnxz presented no evidence to support this belief, other than that ripe individ- 

 uals disappear fromi the Chiba sea region and then reappear further northward in spent con- 

 dition. From July to November the tunas are taken in the vicinity of Hokkaido. A migration 

 southward then occurs, but the fish are not schooled and are spread over a wider area than 

 during their northtrard movement. After they leave the Hokkaido and Tohoku regions the shoals 

 appear In the offshore waters east of Honshu. Two general paths southward seem to be indica- 

 ted, one along the eastern side of the Kuroshio Current, and one in the raid-Pacific region. 



The black tunas moving southward from the Shlkoku sea region ajspear In the waters 

 of the Bonin'^Oalto-it^ukyu area between May and July in ripe condition. It Is believed that 

 the group spawns In this area since spent individuals are also taken here. 



Curing August very small black tunas, about six inches in length, have been taken 

 In great numbers along the coast of Shisuoka Prefecture (Klmura, MS). Possibly they are the 

 young of adults that have spawned In the Islands of the southern latitudes. 



On the west coast of Japan the black tunp follows a similar seasonal sequence in 

 its northward migration. Tagging experiments, the only ones successfully attempted by the 

 Japanese with any of the tunas, were made on the black tuna by the Hokkaido Experimental 

 Station at Tolchl and offer some evidence on the movements of the species. Kawana (1934, 

 pp 10-11) released nine tagged fish at Tolchl on 8 July 1932. Three of these were recap- 

 tured In the same vicinity 23, 60, and 93 days later. Of 39 tagged fish liberated In the 

 sane vicinity on 28 September 1932, three were recaptured, two close to Yolohl and one at 

 Morohashl, Ishlkawa Prefecture, west central Honshu. The author concluded that in the summer 

 months the fish remain in almost the same water, but with the drop In temperature In the fall 

 they migrate south along the west coast of Honshu. 



Philippine Stock; Black tunas are first seen in the Philippine area about 20 March, 

 when they appear In the waters around Plates Island. During April and May large schools of 

 the fish disperse Into the broad area between Formosa and northern Lueon and are In sufficient 

 numbers to warrant Intensive commercial operations. These schools begin to migrate north- 

 ward and are found In the southern Byukyus during late May and June. 



The spawning behavior of the Philippine schools has not been determined, but many 

 ripe individuals have been taken in the Formosa-Philippine area during the middle of May. 

 In June, however, the fish In the southern ^jrukyus were spent. 



4. Ooeanographle Data 



Data on catch statistics in relation to water tenperature and the moveaentt of water 

 oarrente are too few to permit gener all <at ions regarding these factors as they affect the dis- 

 tribution of Hjim black tuna. The studies reported In the literature, however, do Indicate 

 that the migration and abundemce of the species In Japanese waters may be directly concerned 

 with ooeanographle conditions, 



Takajrama and Ando (1934, pp 6,30) analysed catch records in relation to eurface water 

 temperature in the fishing grounds off the eourthern half of the Japanese Pacific coast. 



22 



P-6307 



