FISHERY BULLETIN VOL 77, NO 



(Figure 18), but growth is nearly constant through 

 the subadult sizes. The vaginal opening is 

 occluded by a partial membrane only in the juve- 

 niles, disappearing by 135 cm. The membrane 

 may be lost with growth. The first attempt at copu- 

 lation would remove it. 



Sex Products 



Another method for determining size at sexual 

 maturity is to examine the sex products (follicles, 

 ova, embryos) in relation to body length. 



The presence of mature ova in the ovary is one of 

 the most widely used indicators of elasmobranch 

 sexual maturity. Metten (1941), Bonham et al. 

 (1949), Kauffnian 1 19.501, Olsen (1954), and 



Springer ( 1960) have all partially utilized the con- 

 dition of ovarian eggs for this purpose. 



In the mature blue shark a generation of 100- 

 130 large ova of fairly equal diameter ( 15-20 mm) 

 visually dominate the hundreds of smaller folli- 

 cles in the ovary. 



In a 243 cm mature gravid female, the most 

 distinctive ovarian features were 123 yolked ova 

 from 6 to 20 mm in diameter. The larger ova were 

 found at the anterior end of the ovary. A second 

 group of nearly 1.000 follicles, from 0.1 to 1.0 mm 

 in diameter, were found between and attached to 

 the covering of the larger ova. 



The diameter of the largest generation of ovar- 

 ian eggs is a valid index of first maturity when 

 compared with body length (Figure 19). First 



1 — I — \ — I — r 



40 60 80 100 



120 140 160 180 200 220 240 260 

 FORK LENGTH (cm) 



Figure 18 — Oviducal outside diameter-body fork length relation.ship in the blue shark. 



458 



