whereas our data cover a different segment of the 

 ocean, from long. 170° E. to 120° W. 



SIZE CHANGES DUE TO SHIFTS IN FISHING 

 GROUNDS 



Since average fish size is known for each area, it 

 is possible to determine to what extent selection of 

 fishing ground is responsible for changes in fish 

 sizes in tlie landings. The shifting of the fishing 

 effort from one area to another is readily seen 

 (table 5). The regular shift of fishing grounds in 

 1964 and 1965 accounted for a large measure of the 

 size changes in the landings. The average size of 

 albacore decreased in Marcli and April of both 

 years when nearly all of the catches came from the 



area north of lat. 10° S. where the fish are 

 smaller. For example, when the average size first 

 began to decrease in February 1964, 68.7 percent 

 of the catch was made between 6° and 10° S., 

 where the albacore are small. During March, April, 

 and May, wlien the average sizes were smallest of 

 the entire year, 84.8, 93.5, and 93.0 percent, re- 

 spectively, of the landings came from this area. 

 The sizes gradually increased as fishing shifted to 

 other areas. The same situation was repeated in 

 1965. In contrast, fishing was less concentrated in 

 these northernmost waters during the early months 

 of 1963. In March, April, and May, for example, 

 only 20.0, 73.0, and 70.3 percent, respectively, of 

 the landings came from lat. 6° to 10° S. 



Table 5. — The monthly mean length of albacore, and (in parentheses) the estimated percentage of the total catch from each 

 locality by American Samoa-based vessels, shown by 6 degrees of latitude in the central South Pacific 



ALBACORE TAKEN IN LONGLINE FISHERY IN AMERICAN SAMOA 



65 



