equatorial region is the only area of spawning, those groups of fish 

 from Hawaii and the Japanese North Pacific fishery would have to make 

 an extensive migration to reach this area. Evidence from connnnercial 

 fishing operations in the western Pacific indicates that there is migra- 

 tion in a north-south direction (Nakannura 1949, Honma and Kamimura 

 1955). 



Further evidence for extensive migration of Pacific bigeye can 

 be seen in modes resulting from measurements of fish at the Equator. 

 Murphy and Otsu (1954) give length frequencies for bigeye measured 

 during the Japanese mothership expeditions west of 180 longitude. 

 These have been plotted using their 5-cm. groups in figure 16. The 

 distributions, which cover June 1950 through October 1951, show that 

 throughout the year a mode is present at about 130-135 cm, (102-114 

 pounds) that does not appear to progress. During September and 

 October of 1951 a lesser mode appears at about 92-97 cm. (37-43 

 pounds) that is not present in the other samples. The lack of modal 

 progression with time indicates a constant movement of bigeye into 

 and out of the depths sampled by the longline gear or into and out of 

 the geographic area fished. The occurrence of modes during Septem- 

 ber and October of 1951 that are not present in the other distributions 

 is also an indication of the migration of a size group into the sampling 

 area. 



Additional evidence of migration is found in the Japanese North 

 Pacific fishery, where there is an increase in abundance of the larger 

 size groups with an accompanying decrease in the smaller size groups 

 as one goes from west to east (Nakanaura et al. 1953). Since it seems 

 safe to assume that the species grows, the difference in size with area 

 indicates that there are regular and perhaps complex migrations. In 

 figure 15 it can be seen that the Japanese catches have snnaller modes 

 (30-40 pounds) than can be found in the Hawaiian catches (the smallest 

 in the Hawaiian data are usually about 80-90 pounds). However, it is 

 also interesting to note that these very small modes appear to be 

 present each year rather than biennially, and that the large modes that 

 occur at about 180-200 pounds in the Hawaiian fishery are not seen in 

 the Japanese fishery. 



By way of review, the modal groups of bigeye tuna in the sever- 

 al areas (fisheries) present several puzzling problems. Near the 

 Equator, where ripe fish are taken, there is no progression of nnodes. 

 In the nnore northern areas, where spawning has not been noted, the 

 modes progress with time, but there is a curious alternation of modes 

 between years when considering a single area. Considering two well 



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