PRATT REPKODUCTION IN BLUE SHARKS 



100 



120 



140 160 180 200 220 



FORK LENGTH (cm) 



240 



260 



280 



Figure 19. — Largest egg diameter-fork length relationship in the blue shark. Hand tit curve follows the first generation of eggs in the 

 subadult population Egg diameters accompanying lengths >200 cm are from mature or gravid females that have released or absorbed 

 one or more generations of eggs and are producing subsequent generations. 



maturity is reached at 180-190 cm body length by 

 this criterion. Egg diameters accompanying body , 

 lengths -200 cm are from mature or gravid fe- 

 males that have released or absorbed one or more 

 generations of eggs and are producing subsequent 

 generations. 



Gravid Females 



The smallest recorded gravid females should be 

 slightly longer, due to elapsed gestation time, 

 than females carrying their first generation of ripe 

 ovarian eggs (Figure 19). Gravid blue sharks with 

 the smallest fork lengths reported in the literature 

 from the Atlantic are as follows: 166 cm (Tucker 

 and Newnham 1957), 193.3 cm (Aasen 1966), 

 and 177-203 cm (Bigelow and Schroeder 1948); 

 from the Pacific: 168cm(Suda 1953) and 173.3 cm 

 (Strasburg 1958). 



Blue sharks carrying embryos are encountered 

 infrequently in the world ocean. Suda (1953) ex- 

 amined 115 Pacific blue shark females bearing 

 embryos and concluded that gestation lasts 9 mo 



and birth occurs between December and April. At 

 this time the embryos have attained a maximum 

 length of 39 cm. Strasburg (1958) examined 18 

 large females from the Pacific of which at least 10 

 were pregnant. The largest embryos were also 39 

 cm and occurred in March and May. 



Francis Williams" caught eight pregnant fe- 

 male blue sharks while longlining in the eastern 

 Pacific. His sample was unique because the size 

 range of gravid females was small (153.3-171.6 

 cm). The embryos also were in a narrow size range 

 (21.9-34.7 cm). 



Gubanov and Grigor'yev (1975) reported small 

 embryos (3.2-28 cm) from February to July in the 

 equatorial Indian Ocean. They speculated that 

 birth of young blue sharks occurs outside of this 

 area. 



"Williams, F. 1977. Notes on the biology and ecology of the 

 blue shark iPrionace glauca L.) in the eastern Pacific Ocean and 

 a review of data from the World Ocean (unpubl. manuscr.l. 

 Pers. commun. via John Casey, Northeast Fisheries Center Nar- 

 ragansett Laboratory. National Marine Fisheries Service, 

 NCAA, Narragansett' Rl 02882. 1977, 



459 



