The length frequencies of bigeye tuna ghow the same marked increase in size from 

 ■west to east as do the yellowfin (fig. 10--this figure is based on the same sources as fig. 9, 

 and includes the measurements from the cruises noted in table 8), There is a suggestion of 

 two size levels in figure 10, with fish west of 180 considerably smaller than those to the east 

 but considering the relatively small number of iifh 'ji each sajnple, the steep gradient center- 

 ing at 180 may be an artifact. 



Table 8. --Length frequencies of bigeye tuna taken by longline fishing gear 



l_/ Stations 1-19 

 Z/ Stations 20-22 

 3/ Stations 23-31 



The samples of albacore and skipjack are inadequate for the type of analysis 

 performed on the yellowfin and bigeye. They are, however, useful in another respect, because 

 they indicate that the longline will take relatively small fish (table 9). The capture of albacore 

 and skipjack is good evidence that the absence of appreciable numbers of small yellowfin and 

 bigeye from the longline catches is due to their absence from the habitat fished on our cruises 

 to the Equator rather than to gear selection. 



SEX RATIOS OF THE TUNAS 



Puzzling discrepancies appear in the sex ratios of tuna teiken on the longline. In 

 previous reports we have noted the fact that males predominate in the catches of bigeye and 

 yellowfin (Murphy and Shomura 1953a, b). With respect to yellowfin, Nakamura (1949) noted 

 that catches made in the East Philippine Sea had equal representation of the sexes up to 122 cm. 



18 



