but between 30 N. and 32 N. the size has become larger, with an average 

 weight of 3. 2 kan /26 lbs. / as compared with 2.4 kan /_20 lb8_^/ in the pre- 

 ceding month. This increase in the size of the fish taJcen between 30 N. 

 and 32 N. is thought to be one bit of evidence for a retrograde movement 

 of albacore which had descended farther south. 



(2) Kinan Ground 



30°N. 



The center of the fishing ground has clearly shifted to north of 

 indicating that the albacore have begun their northward migration. 

 Catch rates continue high as in the preceding month, and there are cases 

 with values above 10. 0. Just as in the sea areas east of the Izu andOgasa- 



wara archipelagoes, the waters north of 30 N. 



Table 2. --Albacore catch 

 rates of the Kinan ground, 



28°-32°N 



133 



140°E. 



continue to offer the most active fishing condi- 

 tions (see table 2). 



The composition of the schools is not 

 known because of a lack of measurement data, 

 but the size of the fish is thought to be approxi- 

 mately the same as that found in the area of 

 28°N. to 32°N. , 140°E. to 150°E. 



2. Grounds South of the Subtropical Convergence 

 A. Grounds in the Area Between ION. and 25 N. 

 (1) Albacore East of the Line of the Izu and Bonin Islands 

 (Albacore of the Southern Zone) 



In the section on the North Pacific fishing ground it was stated that 

 the albacore of the northern and southern zones differ markedly with regard 

 to fishing conditions and size composition. The size composition of albacore 

 taken in the southern zone is shown in table 3, 



Table 3. --Size composition (actual 

 numbers) of edbacore landed from 

 the southern zone (nnid-latitudes 

 east of the Bonin Is.). 



B 



ft 



L 



Fish measured. 



95— 105cm ]>105cmaj; 



21 



57 



¥■ ^ <* ffi: 



Mean weight. 



6.971 



The catch is composed 

 entirely of large albacore and thus 

 differs conspicuously from the size 

 composition on the North Pacific 

 fishing ground. The catch rates 

 are not very high, with a continuous 

 line of areas showing values of around 

 0, 1 to 0. 5. This sort of ground 

 appears not only in the southern 

 zone, but seems to extend far 

 southward to the vicinity of 15 N. 



115 



