fact that the isotherms have drawn closer together than they were in 

 January and have moved about 1 farther south. 



The catch rates continue to be at high levels, as they were in 

 January. On the North Pacific fishing ground the overall average catch 

 rate per unit area for January was 3.83, and in February it is 3.98 (in 

 March it drops off abruptly to 2.42). In table 1, the sea area is divided 

 into smaller segments of 2 of latitude by 5 of longitude in order to show 

 the changes in the catch rates from month to month; the pattern of areas 

 in which the catch rates have increased, and areas in which they have 

 decreased, is extrennely complex. 



Table 1. --Monthly changes in the catch rates in 

 each 5 degrees of longitude 



Agreement in the monthly changes in the catch rates is apparent 



as between the areas of 140°E. to 145 E. and 145°E. to 150°E., and 



o o o o 



again as between 170 E. to 175 E. and 175 E. to 180 , however, no such 



anadogies appear in the area centered around 160 E. In general the north- 

 south extent of the fishing grounds is extraordinarily narrow, and it is 

 thought that within this sphere the southward-moving albacore are com- 

 pressed to the maximum, giving rise to the high catch rates. 



Differences fronn year to year in the catch rates are rather well 

 marked. As can be seen in table 2, the catch rates were higher in 1949 

 and 1952 than in 1950 and 1951, being particularly high in 1952. The 

 annual ups and downs of the catch rate appear to be characteristic for 

 the fishing ground as a whole, and in 1949 and 1952 catch rates were gen- 

 erally high everywhere between 140°E. and 180°, while in 1950 and 1951 

 they were generally low. This is thought to indicate that the North Pacific 

 fishing ground is, as a whole, under a single regime. 



82 



