distribution amd migration on the basis o£ catch rates. If we connpare the charts a to e referred 

 to above with the chart of migrations prepared by Uda, 



1. At the beginning of the fishing season there are three groups of fish appearing 



separately in different areas. That is, in November the area centered around 



o , o 



150 E. and that centered at 165 E. each have one group, but in December the 



boundary between these two groups becomes unclear, while in the Kinan sea area, 



a group of schools completely separate from these two appears. 



2. The subtropical convergence is a boundary, with the distribution of albacore to the 

 south, that is, in the North Equatorial Current, quite vestigial, while the dis- 

 tribution is extremely dense to the north of the convergence. 



On these most important points, there is cleaurly agreement. How- 

 ever, with regard to the migration routes, 



3. It is difficult to detect with certainty any fixed direction except that the schools 



to the east of 165 E, longitude are already densely congregated in the vicinity 



of 30 N. by the middle of November, and both the schools distributed around 



o , o 



150 E. and those around 165 E. move slowly to the south with the passage of 



time. It can be seen that the schools in the vicinity of 150 E. tend to move to the 



southeast. 



4. On the whole the schools appear to become gradually densely congregated within 

 aji area just like a rising tide, but the migrationcil routes by which the schools 

 move there are not clear. This tendency appears most clearly in the Kinan sea 

 area. 



Thus, certain differences are apparent, however, Uda's conclusions are based on 

 data from only about 1 year, while the data presented here cover a number of years, in some 

 cases more than 10 years, and therefore it may be thought that differences from year to year in 

 the pattern of migration may have obscured the niigrational routes. 



As was stated earlier, it is impossible under present conditions to correct the catch 

 rates for differences resulting from the fishing gear. The longlines used on fishing grounds 

 south of 30 N. , particularly fishing grounds in the vicinity of islands, differ somewhat, as has 

 been said, fronn the gear especially designed to take albacore. It is, however, probably no 

 mistake to consider that the differences in catch rates in waters north of the North Equatorial 

 Current cind in those to the south clearly indicate a difference in the density of distribution of 

 the albacore. 



C, Bigeye Tuna 



Appendix chart III shows the distribution of catch rates for bigeye tuna in the Indian 

 Ocecin, the western Pacific, cind their contiguous sea areas. As the chart makes clear, the dis- 

 tribution of the bigeye tuna is extremely broad, extending from the Equator to 40 N. Little 

 difference in the density of distribution throughout the whole region can be seen from the catch 

 rates. In other words, the center of distribution is not clear. 



The chart represents catch rates throughout the year, and shows that the catch rates 

 in the South China Sea are greater than those in the Sulu Sea 2ind the Celebes Sea. Leaving these 

 contiguous waters out of consideration, the general picture in the Pacific is as follows: 



1. South of 10 N. there is an area off Mindanao where the catch rates are rather 

 high, and farther to the east from about 140 to 160 E. there is another area of 

 high catch rates. 



145 



