Among the areas shown in figure 1 there are data for each month 

 covering the fishing grounds fronn north to south for the section of 140 E. 

 to 150 E. , so here the movements of the fishing grounds can be quite 

 clearly deduced. In the early part of the fishing season, i.e. , in October 

 and November, the catch rates are generally higher in the north and drop 

 off gradually to the south, with the southern extremity at 3 1 N. It is im- 

 possible to make any assertions concerning the conditions which define 

 this southern limit, but there is a barrier to distribution and nnigration 

 and this barrier moves southward with the passage of the season until 

 it reaches the vicinity of 25 N. Looking at the variations in the catch 

 rates, we see a tendency for the schools to accumulate gradually in the , 

 waters along the northern side of this barrier, a condition whichNakamura— 

 has pointed out in support of his idea that this is a feeding migration. For 

 the areas east of 150 E. data are fragmentary so the situation is not well 

 known, but in its tendency it appears to resemble the area of 140 E. to 

 150 E. The quauitity of schools present is, of course, high in this area 

 of accumulation, but the catch rates, at any rate, trail out far to the north 

 up to January and show a considerably dense distribution in the north also. 



It cannot be stated at present what the barrier is that defines the 

 southern limit of the grounds, but judging from the pattern of southward 

 movement of the fishing grounds it is thought that the most powerful influ- 

 ence is the Subtropical Convergence, and this is considered to show the 

 correctness of Uda'sz.' view that the southern limit of migration is con- 

 trolled by the Subtropical Convergence. 



In any case, the positions in which the albacore fishing grounds 

 of the North Pacific develop and their form coincide well with the areas 

 of flow of the Kuroshio and the North Pacific Current, and it is thought 

 that a thorough study should be made of the relationship between these 

 currents and the fornaation «md movements of the fishing grounds. 



Considering in terms of figure 1 the variations in speed from year 

 to year of the southward movement of the schools between 140 E. and 

 150°E., it is deduced that in 1950 (November 1950 to March 1951) the 

 main schools were located farther north in November thaji they were in 

 the same month of 1949 (November 1949 to March 1951), but in December 



7/ 



— Nakamura, Hiroshi, Nankai Regional Fisheries Research 



Laboratory, Report No. 1, 144 p., 1951. 



- Uda, Mi< 

 pp. 295-300, 1937. 



8/ 



— Uda, Michitaka. Bull. Jap. Soc. Sci. Fish., Vol. 5, No. 5, 



30 



