lower in the west. Albacore also appear to exhibit a tendency to be high in the east and low in 

 the west. The highest spearfish catch rates are in the section of 146 to 148 E. 



o o 



Table 59. --Fishing conditions by sections (25 to 30 N. , 



140° to 150° E.) 



Between 25 and 30 N. , as table 59 shows, black tuna have been taJ^en only in the 

 section from 140 to 144 E. Yellowfin catch rates are highest in the west and tend to decrease 

 gradually to the eastward, and similar trends appear for bigeye tuna and spearfishes. Albacore 

 show the opposite trend, with catch rates low in the west and increasing gradually to the east. 



In tables 58 and 59 no account at all is taken of the seasons, but it is clear from 

 tables 56 and 57 that there are notable seasonal changes in fishing conditions. However, if the 

 data in tables 58 and 59 are considered with attention to seasonal differences, these few data are 

 further extended and diluted to the point where they do not have much significance. As tables 56 

 and 57 show, for the area from 20 to 25 N. there are more data for the summer (April to 

 September) than for the winter (October to March). For 25 to 30 N., on the contrary, there are 

 nniore data for the winter season, more than twice as nnuch aa for the summer, and this fact must 

 be talten into consideration in connparing fishing conditions in the two areas. 



Another problem which must be tauken up together with the changes in the fishing 

 conditions from season to season is that of the changes produced by differences in the fishing gear. 

 This problem is not limited to only this sea area. The gear used in the winter north of 25 N. is 

 mostly the so-called albacore line, and in view of its construction it goes without saying that some 

 correction is necessary in order to judge the fishing conditions solely on the basis of catch rates. 

 However, on the one hand, most of the data do not record the construction of the fishing gear and 

 thus afford no clear basis for a correction, and on the other hand, as was set forth in Chapter 7, 

 there is no accurate method of making such a correction. Consequently, in evaduating the fishing 

 conditions for these species, and in considering the pattern of their distribution, the catch rates 

 for yellowfin, bigeye tuna, and spearfishes north of 25 N. latitude cannot be said to have exactly 

 the same significance as the catch rates south of that latitude. The same thing is true of the 

 albacore. However, it is probably possible to discuss the patterns of distribution in terms of 

 trends. 



This sea area can be thought of as a comparatively stabilized fishing ground throughout 

 the year. In the southern portion in December and Jainuary and for a few months in the summer 

 the catch rates are high and the principal catch is spearfishes. In the northern part the catch 

 rates are high from Jainuary through March and from May through July, with albacore the princi- 

 pal catch in the winter aind spearfishes in the summer. Among the spearfishes taken in the 



93 



