Skomal and Natanson; Age and growth of Prionace glauca 



637 



oceans (Suda, 1953; Tucker and Newnham, 1957; 

 Aasen, 1966; McKenzie andTibbo, 1964; Dragonik 

 and Pelzarski. 1983; Stevens, 1984; Francis et al,, 

 2001 ). Although the largest blue shark reported 

 from the North Pacific was only 254 cm FL (Stras- 

 burg, 1958; Cailliet et al., 1983), individuals up to 

 331 cm FL have been reported from the South Pa- 

 cific and the largest sharks were all males (Francis 

 et al., 2001). The paucity of females exceeding 225 

 cm FL in the current study and the complete lack 

 of these specimens in the Stevens (1975), Silva et 

 al. (1996), and Henderson et al. (2001) samples 

 indicate that these fish are rare, inhabit unknown 

 or unfished areas of the Atlantic, or possibly avoid 

 fishing gear In our study, the VBGF parameters 

 (Table 5) show that females theoretically attain 

 larger sizes than males. However, the low number 

 of large females in this and previous studies may 

 indicate that natural mortality prevents them from 

 attaining these lengths. The occurrence of severe 

 lacerations on female blue sharks incurred during 

 courtship is well documented (Stevens, 1974; Pratt, 

 1979). Although highly speculative, the long-term 

 cumulative effects of such behavior may act as 

 a source of increased mortality in females of the 

 species, shortening their life-span and limiting the 

 number that reach the larger sizes. 



Through an integrated approach incorporating 

 vertebral banding, OTC injection, and tagging 

 data, it has been shown that the blue shark grows 

 faster and lives a shorter life than previously 

 thought in the North Atlantic. We believe that 

 the validated vertebral interpretations generated 

 during this study for the first four years of growth, 

 combined with the vertebral counts and longevity 

 estimates from tag-recapture data, provide vigor- 

 ous estimates of age and growth for a large pelagic 

 carcharhinid, the blue shark. 



Acknowledgments 



We thank the many people who contributed to 

 the success of this study on research vessels, at 

 recreational fishing tournaments, and on board 

 private, chartered, and commercial fishing vessels. 

 This study would not have been possible without 

 the staff of the NMFS Apex Predators Program 

 (Narragansett, RI) including Nancy Kohler, Pat 

 Turner, and Ruth Briggs. We especially thank 

 retired NMFS researchers Jack Casey and H. 

 Wes Pratt for giving the senior author the tools 

 necessary to initiate and complete this work. We 

 are grateful to shark-aging pioneer Gregor Cailliet 

 for his moral support and relentless pursuit of this 

 publication. We are indebted to the thousands of 

 fishermen who voluntarily tagged and returned 

 sharks for the NMFS Cooperative Shark Tagging 

 Program. This study was partially funded with 

 support from the Sportfish Restoration Act. 



300 



A Tag/recapture-GROTAG 



Tag/recapture-Gultand method 



Vertebrae-current study 



Aasen (1966)-LF modes 

 ' Henderson el al (2001) 

 Silva etal. (1996) 



2 4 6 8 10 12 14 16 18 



B 



Vertebrae-current study 



/ Silva etal (1996) 



12 14 16 18 



250 



2 4 6 8 10 12 14 16 



Age (years) 



Figure 8 



Von Bertalanfly growth curves generated from vertebral and recap- 

 ture data for (A) sexes combined, (B) male, and (C) female Prionace 

 glauca, as compared to OTC-injected recaptured blue sharks; included 

 for comparison are the von Bertalanffy growth curves of other North 

 Atlantic studies. 



