In the northweBtem Pacific Ocean the altacore 1« abundantly distrlhuted throueh- 

 oat an area extending east from the coast of Japan for about 2|000 miles and situated north 

 of the line of convergence between the North Equatorial and the North Pacific currents 

 (compare Flares 2, 3, and 10). This species has not been reported froir. the Sea of Japan. 

 Albacores have b'^en tsJcen from March to September in email quantities by experimental vessels 

 exploring the waters of the former Jnpanece Mandated Islands for this species and by vesEele 

 nperBtlng for yell<Twfin tuna in these same areas. During the winter aaontne these operations 

 were on a small sc&ie but a few reports indicfite that the albacore may occur in scattered 

 shoals over a wide area at that eefisnn of the yefir. 



Uda and Tokunaga (1937), In the most comprehensive study to date on the albacore. 

 endeavored to analyze the various stocks present In the areas directly east of Japan. The 

 seasonal changes In the fishing grounds were Investigated and correlated with the size of 

 the specimens and hydrographlcal features. Their conclusions, liowever, are based on inad- 

 equate data, and the designated migratory routes are largely hypothetical. Nevertheless, 

 they are reported below. 



The two major fishing grounds for the albacore In the northwestern Pacific Ccaan 

 are the sunnier grounds situated near the Japanese coast ajid the winter grounds In the rald- 

 Paclflc region (Figure 10). As the temperature of the water along the Japanese coast rises 

 and the Kuroehlo Current advances, the coastal schools begin their mlsratlon northward from 

 the Shlko)cu region about April or May. They continue their migration through the Izu Islands 

 chain and by June or July enter the Toho)cu region. The majclmam catches of "Bumr.er" albacore 

 are obtained during Kay and June. The fish belonging to the coastal group are small, the 

 majority of the indivldualp weighing less? than 19 kilograms. Uda .-.nd ToVrunaga aeeumed that 

 the coastal albacores, v/hich disappear pudfienly during July, migrate southward along the 

 east side of the Kuroshio Current. 



The shoals In the mld-Paclflc (occurring 1,000 to 2,000 miles offshore) appear in 

 great abundance during the winter months and constitute the most productive albacore fishing 

 grounds. The season begins In October, reaches a maxinum from December to February, and ends 

 in April. Uda and Tokunaga believed that the bulk of the mld-Paciflc albacores perform a 

 year-round migration In a large circle. From December to April the fishing grounde grad'oally 

 move southward toward the area of convergence between the North Pacific and the North Bquator- 

 lal currents In the region between 160° and 180°K longitude (Figure lO). Whether these 

 schools turn eastward or westward upon reaching the line of convergence Is uiujertaln, but 

 albacores have been taken In the region north of the line between 150° and 160°i! longitude. 

 For this reason the authors believed that the mld-Paclflc schools turn westward and migrate 

 Into the region directly east of the Izu Islands (about 145° to 150°i; longitude and 25° to 

 35°N latitude). Turning northward from this point the fish are seen In the waters between 

 150° and 170°B longitude In the latitudes where the Kuroehlo Current Is running eastward. 

 The fish taken in the mld-Paclflc waters are mostly large, weighing 19 or more kilograms, 

 although smaller ones are Intermingled. 



The above theory concerning the stocks and migrations of the albeicore was based on 

 Inadequate data; moreover, the fish were obtained by different methods in the two major fish- 

 ing grounde, thus making comparison of stocks unreliable. For example, the coastal albacores 

 were taken mainly by hook and line operated by vessels of about 40 to 70 tone, whereas the 

 mid-Pacific fish were obtained with long lines operated liy vessels over 100 tons. Consequent- 

 ly, the fishing methods were selective in favor of smaller albeicores being obtained from the 

 coastal grounds and larger ones from the mld-Paclflc area. The Information Is presented here 

 merely because it is the only work of anj' consequence that has been done on the albacore. 

 Other workers claim that there is only one stock in the northwestern Pacific Ocean, and that 

 the schools in It make a great circular migration over the entire area discussed above. Too 

 little is known about the albacores obtained in the ^rukyu area and in the former Mandated 

 Island region even to Indicate their possible relationships to the individuals taken In the 

 northern latitude*. 



P-6307 



