Fujinami et al.: Age determination and growth of Prionace glauca in the western North Pacific Ocean 
1 1 7 
Age (years) 
Figure 6 
Maturity ogives for (A) male and (B) female blue sharks (Prionace glauca) 
and (C) maternity ogive for female blue sharks captured in the western 
North Pacific Ocean during 2010-2016. The dotted lines indicate 95% con¬ 
fidence intervals. Also provided are the age at 50% maturity (A 50 ) as well 
as the coefficients a and (3 with standard errors (SEs). 
One possible reason for the variation is that growth 
and sexual maturation may have changed concomitant 
with declines in shark abundance during the 1980s, 
but, along with a rebounding of this population dur¬ 
ing the mid-1990s and 2005, these parameters might 
have recovered to and reached values comparable to 
pre-decline levels of the 1980s. Alternatively, the rapid 
stock fluctuation of the 1980s and 1990s might have 
had no effect on growth and maturation of blue sharks 
of the North Pacific Ocean. Reproductive parameters 
(e.g., size at maturity and gestation period) of sharks 
in the western North Pacific Ocean during 2010-2016 
(Fujinami et al., 2017) differ little from those reported 
by Nakano (1994) for the period from 1978 to 1987. 
