If in this species the sexes were subject 

 to differential mortality but not to differential 

 growth, the observed male and female modal 

 groups should be nearly identical in position prior 

 to the onset of the differential mortality, the 

 sex ratio changing as the mortality occurs. This 

 is not definitely indicated; rather, there is sonne 

 evidence suggesting differentizd growth. 



In figures 7 and 8 it caji be seen that among 

 the prominent modal groups the female curves are 

 displaced to the left of the males. A clearer dis- 

 placement of the female mode would be evident if 

 the frequencies were given as percentages instead 

 of absolute numbers, for when absolute numbers 

 are used the left tail of the male nnodad group 



conceals the displacement of the left tail of 

 the femjile modal group. 



Size Differences with Area 



An increase in the nneaji size of 

 yellowfin in longline S2imples taken along the 

 Equator from west to east has been noted 

 (Murphy and Shomura 1953). The present anal- 

 ysis involves yellowfin caught in two areas 



o o 

 bounded by about the same latitudes (0 -5 N. ) 



but by different longitudes: 155 W. to 180 and 

 140°E. to 179°E. (fig. 1). The distributions 

 for the central equatorial (155 W.-180 ) area 

 are in figures 7 and 8; those for the more 

 westerly area are shown in figure 9. Although, 



LENGTH IN CENTIMETERS 



Figure 7. --Length-frequency distributions of equatorial 

 yellowfin from 155 W. to 180 longitude taken during 

 1951-1953. 



