passed until smaller fish of about 490 pounds were taken at the end of the season. It is very 

 regrettable that there are no data to show this concretely. However, full account should be 

 taken of this difference in the size of the individual fish. 



The second point is the question of fishing seasons. As has already been said, about 

 the time the schools in the waters around Tanegashima began to move slowly to the northeast, 

 there was already a certciin amount of fishing being done in the South China Sea. As was stated 

 earlier, there is also a theory that the schools nnove south from the vicinity of Toi Misaki, and 

 the coincidence of fishing seasons is not necessarily proof of the difference or identity of the 

 schools. It is believed, however, that this coincidence of fishing seasons, together with the 

 distance between the fishing grounds and the movements of the schools in the waters around 

 Tanegashima, has a considerable significance as indicating the distinctness of the schools. 



The third problem to be considered is the question of the sexual maturity of the two 

 groups of schools. There have been absolutely no reports of fish with ripe or near-ripe gonads 

 from the schools in the waters jiround Tanegashima, even at the end of the fishing season. It is 

 believed that July is the center of the spawning season for black tuna in Japanese coastal waters 

 (including the Japan Sea). In fish from the schools of the Luzon area the gonads are already very 

 well developed at the beginning of the fishing season, in April and May the majority of the fish 

 are ripe, and by the early part of June spawned-out fish already appear in the catch. As it is 

 thought that these fish characteristically spawn over a rather long period and throughout a broad 

 area, this difference in ripeness of the gonads cannot be said to have absolute significance as 

 indicating the distinctness of the schools. Thus at present we have no data which would enable 

 us to prove definitely the relationships between the schools which appear in these two areas and 

 we must therefore wait for future studies to be made. However, the three points cited may be 

 considered to indicate the distinctness rather than the identity of these schools. 



B. Albacore 



The appended chart II shows the distribution of catch rates for albacore. As has 

 already been stated, the albacore is broadly and generally distributed in the western Pacific 

 Ocean north of the Equator to the vicinity of 40 N. latitude and it also occurs to some extent in 

 the South China Sea and the Sulu Sea. It can be said, however, that the area in which the catch 

 rates are particularly great, or in other words where the density of distribution is high is the 

 area from 25 to 40 N. latitude. Accordingly it can be said in extremely general terms that the 

 main fishing grounds are in the area north of the Northern Equatorial Current, that is, north of 

 25 N. , in the Kuroshio and its extension, the North Pacific Current. 



Considered seasonally, this species occurs to some extent at all times of the year 

 ■ omewhere in the northern part of the western Pacific. The season of densest occurrence, how- 

 ever, is from November to March, particularly from December to February. 



As our data are extremely uneven in their representation of areas and seasons, it is 

 impossible to clarify the distributional pattern for each sea area throughout the year. If we 

 select two or three sea aireas for which data are connparatively adequate throughout the year, 

 and plot the changes in the fishing conditions from month to month in those sea areas, we get the 

 picture shown in the following figure. 



o o ^o 



Figure 15 shows the fishing situation in each month in the area to 5 N. , 150 to 



160 E. In December, February, and March the catch rate is 0. Some fish are tciken in all 

 the other months, the catch gradually increasing from July on, with the highest catch rate of the 

 year in September. The catch rate declines sharply in October, showing only a vestigial occur- 

 rence. 



141 



