20 



Fishery Bulletin 92(1), 1994 



rates (AGR, mm/day or g/day) were predicted for the 

 initial 365 days (Table 4). 



The slopes of the size-at-age regression equations 

 for females from the western North Pacific were 

 significantly different from those for both central 

 North Pacific males and females (Fig. 6, Table 5). 

 Comparisons of regression slopes between central 

 North Pacific males and females revealed no signifi- 

 cant differences in length or weight-at-age relation- 

 ships (P=0.424, P=0.307). Testing of elevations from 

 the central North Pacific male and female data iden- 

 tified a significant difference (P<0.001, Table 5); 

 therefore, males and females in the central North 

 Pacific grow in length and weight at a similar rate, 

 but females display a significantly greater size at 

 age than males (Table 4). 



Back-calculated hatching dates 



Backcalculation of hatching dates demonstrated 

 that O. borealijaponica hatched in all months except 



March (Fig. 7). The distribution of hatching dates 

 was not necessarily related to spawning intensity, 

 as more subadult squid were available for age analy- 

 sis than paralarvae and juveniles. Subadult and 

 adult squid captured from July to September in the 

 North Pacific had similar hatch dates as samples 

 collected from the western (August-February), cen- 

 tral (July-February), and eastern North Pacific (Au- 

 gust-November). Paralarval and early juvenile 

 squid captured in the central North Pacific during 

 August 1991 were estimated to have hatched be- 

 tween February and June, 1991. 



Maturity stage-age relationships 



Maturity stages were closely related to squid size for 

 all three sampling areas; males, however, matured 

 at a smaller size than females (Fig. 8). Females and 

 males recruit to the driftnet fishery after attaining 

 maturity stages III and IV, respectively. No mature 

 females (stage V) were captured by any sampling 



