FISHERY BULLETIN: VOL. 73, NO. 4 



similar analysis covering a period from 1963 to 

 1965, seasonal and geographical differences in 

 CPUE were not readily apparent (Otsu and 

 Sumida 1968). For some reason that is not 

 immediately clear, a distinct seasonal pattern in 

 geographical differences in CPUE has developed 

 in recent years. In the first quarter, there ap- 

 peared to be no pattern in the distribution of areas 

 with high CPUE (greater than five albacore per 

 100 hooks). However, the CPUE was better in the 

 east-west extremes of the fishery. In the second 

 and third quarters, an area of high CPUE 

 developed between lat. 25° and 40°S. The fishery 

 was also well developed north of lat. 20°S in the 

 second and third quarters but as in the first 

 quarter there were no well-defined areas of high 

 CPUE. The situation in the fourth quarter revert- 

 ed to approximately what it was in the first 

 quarter. However, in some years there was a ten- 

 dency for an area of high CPUE to develop in the 

 eastern extreme of the area fished between lat. 10° 

 and 20°S. 



Because of geographical and temporal varia- 

 tions in the distribution of the fishing effort, the 

 description of the geographical and temporal 

 changes in CPUE as given above is incomplete. As 

 noted earlier, very little fishing effort was ex- 

 pended south of lat. 20°S in the first and fourth 

 quarters. It would be of interest to determine 

 whether a high CPUE could be obtained south of 

 lat. 20°S also in the first and fourth quarters. The 

 possibility exists, of course, that very little effort 

 was expended south lat. 20°S in the first and 

 fourth quarters because the fishermen know from 

 past experience that poor catch rates are obtained 

 during those periods. Honma and Kamimura 

 (1957) suggested that albacore in the South Pacific 

 make north-south migrations and that the fishing 

 vessels follow the movements of the albacore. In 

 the eastern Pacific tuna fishery, Griffiths (1960) 

 showed that the bait boat fishermen were able, on 

 the average, to concentrate their effort on high 

 densities of yellowfin tuna about 70% better than 

 if their effort had been random. The data indicate 

 that the fishermen may be able to predict the 

 movements of the albacore with some degree of 

 success in that areas of high fishing effort were 

 usually associated with areas of high CPUE. There 

 were quarters, however, in which areas of high 

 fishing effort did not coincide with areas of high 

 CPUE. Then, too, the fishermen may avoid fishing 

 south of lat. 20°S in the first and fourth quarters 



because of bad weather or unfavorable conditions. 

 One other interesting observation is the division 

 of the fishery at lat. 20°S. As noted above, the 

 fishery develops north or south of lat. 20 °S but 

 seldom straddles it. This appears to be a well-es- 

 tablished phenomenon, for Koto (1966) has made 

 the same observation. Koto mentioned belts of 

 high catch rates in the area between lat. 10° and 

 20°S and between lat. 20° and 30°S, and a belt of 

 low catch rates centered at lat. 20°S. The data also 

 indicate that the latitudinal belt centered at lat. 

 20°S is also a low-effort area. The causes of this 

 phenomenon are not clear. 



SIZE OF ALBACORE 



Because the canneries have changed the method 

 of handling the fish, the albacore that are sampled 

 for length are no longer being sexed. Con- 

 sequently, in the analysis of the length distribu- 

 tion of albacore only the data collected from 1966 

 to 1970, when sex data were available, are 

 presented. 



A composite length-frequency distribution of 

 male and female albacore taken by the fishery 

 from 1966 to 1969 is shown in Figure 12. The fish 



UJ 



o 



MALES 



(N = 91,526) 



-^TfmrfTTI 



k^ 



50 60 70 80 90 100 1 10 120 



70 80 90 



FORK LENGTH (cm) 



Figure 12.-Composite length-frequency distributions of al- 

 bacore, 1966-69. 



762 



