FISHERY BULLETIN VOL, 77. NO, 2 



There are few published accounts of gravid 

 female blue sharks in the North Atlantic. Aasen 

 ( 1966) examined 48 caught by longline primarily 

 around the Canary Islands. He reported lengths of 

 11 individuals and embryo lengths from only 2 

 specimens with means of 28.1 and 40.0 cm. The 

 largest embryo length he measured was 43.0 cm. 

 From these lengths he concluded that birth oc- 

 curred between February and April. 



Beebe ( 1932) reported a gravid female taken off 

 Nonsuch Island, Bermuda, in September of 1931. 

 She carried 50 embryos averaging 8.3 cm long. 

 Tucker and Newnham (1957) reported a small 

 ( 166 cm) gravid female caught in the sport fishery 

 off Looe, England. They summarized the eastern 

 Atlantic and Mediterranean observations of 

 gravid females with embryos. 



From 1967 to 1975, 1 examined 19 gravid female 

 blue sharks from the western Atlantic. These 

 specimens include a blue shark taken in January 

 approximately 300 mi northeast of the Windward 

 Islands (lat. 21°20' N, long. 58°52' W); 2 caught in 

 the Gulf Stream south of Sable Island in May; and 

 16 obtained from off the coast of Long Island, N.Y. 

 These fish were caught within 50 mi of shore dur- 

 ing June and July. The embryos from 13 fish were 

 examined, the remainder having been lost or 

 aborted during capture. In addition, Richard 



Backus' has supplied information on 19 gravid 

 females. 



Embryos 



Growth of the placentally viviparous embryos 

 appears to be linear, gestation taking 9-12 mo. 

 Figure 20 combines all available North Atlantic 

 and Mediterranean data for a summary of embryo 

 length and season. The trend line seems to indi- 

 cate a gestation of 12 mo, 3 mo longer than re- 

 ported by Suda (1953). A 12-mo gestation also 

 agrees with my proposed sexual cycle. However, 

 since the left-hand data points are from offshore 

 observations and the right-hand points are from 

 inshore fish, it is quite possible that the offshore 

 embryos may be born in March while embryos 

 from inshore females could have been conceived in 

 September and born in June, 9 mo later. These 

 data cannot therefore resolve gestation time. 



On 23 July 1978, a female blue shark in the first 

 stages of pregnancy was examined at Montauk. It 

 contained two embryos 11 and 13 mm long at- 

 tached to 22 mm yolks with 38 less-developed eggs 

 arranged in a dorsoventral series in both uteri. 



'Original data from Richard H. Backus of Woods Hole 

 Oceanographic Institute. Pers. commun, via John Casey. 



I 

 I- 



a. 

 o 



o 



>- 

 tc 

 m 



UJ 



MONTH OF CAPTURE 



Figure 20. — Embryo length-month relationship for North Atlantic and Mediterranean blue sharks 



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