112 
Fishery Bulletin 1 1 7(1-2) 
D Concave 
□ Convex 
□ Opaque 
□ Translucent 
Month 
Figure 4 
Monthly changes in frequency of occurrence for (A) convex and concave 
structures observed on vertebral centra of blue sharks (Prionace glauca) 
less than 200 cm precaudal length (PCL) and (B) translucent and opaque 
band pairs observed on centrum edges for blue sharks larger than 200 cm 
PCL. Sharks were captured in the western North Pacific Ocean during 
2010-2016. The black dots denote the probability of an annual cycle for 
growth-band formation, predicted by using the model of Okamura and 
Semba (2009). The numbers above bars represent monthly sample size. 
and the counts for 61 samples (30.5%) differed by 
only one band. For intra- (reader 1) and inter-reader 
(reader 1-2) evaluations of precision, the IAPE values 
were 3.7% and 5.3% and the CV values were 4.2% and 
5.9%. No pre-birth band was apparent on near-term 
embryos captured in May, but one growth (narrow) 
band was apparent on neonates captured in late June 
and July. 
Monthly characterization of the centrum edge dif¬ 
fered throughout the year both for specimens less than 
200 cm PCL (n=1066) and for specimens greater than 
200 cm PCL (n=169) (Fig. 4). The proportion of con- 
