627 



Abstract— Age and growth estimates 

 for the blue shark [Prionace glauca) 

 were derived from 411 vertebral centra 

 and 43 tag-recaptured blue sharks col- 

 lected in the North Atlantic, ranging in 

 length from 49 to 312 cm fork length 

 (FL). The vertebrae of two oxytetracy- 

 cline-injected recaptured blue sharks 

 support an annual spring deposition 

 of growth bands in the vertebrae in 

 sharks up to 192 cm FL. Males and 

 females were aged to 16 and 15 years, 

 respectively, and full maturity is 

 attained by 5 years of age in both sexes. 

 Both sexes grew similarly to age seven, 

 when growth rates decreased in males 

 and remained constant in females. 

 Growth rates from tag-recaptured 

 individuals agreed with those derived 

 from vertebral annuli for smaller 

 sharks but appeared overestimated for 

 larger sharks. Von Bertalanffy growth 

 parameters derived from vertebral 

 length-at-age data are L^ = 282 cm FL, 

 A' = 0.18, and t„ = -1.35 for males, and 

 L, = 310 cm FL, K = 0.13, and ig = -1.77 

 for females. The species grows faster 

 and has a shorter life span than previ- 

 ously reported for these waters. 



Age and growth of the blue shark (Prionace glauca) 

 in the North Atlantic Ocean* 



Gregory B. Skomal 



Massachusetts Division of Marine Fisheries 

 Marthas Vineyard Research Station 

 PO Box 68 



Vineyard Haven, Massachusetts 02568 

 E-mail address: Gregory.SkomaiiSlstale.ma.us 



Lisa J. Natanson 



National Manne Fisheries Service, NOAA 



28 Tarzwell Dr. 



Narragansett, Rhode Island 02882 



Manuscript approved for publication 

 5 March 2003 by Scientific Editor 



Manuscript received 4 April 2003 at 

 NMFS Scientific Pubhcations Office. 



Fish Bull. 101:627-639 (2003). 



The blue shark {Prionace glauca) is 

 a large pelagic carcharhinid that is 

 widely distributed in the world's oceans. 

 Throughout its range, it is considered 

 the most abundant species of large 

 shark (McKenzie and Tibbo, 1964; 

 Casey, 1982). In the Atlantic, the blue 

 shark is distributed from Newfoimdland 

 to Argentina in the west and Norway to 

 South Africa, including the Mediter- 

 ranean, in the east (Compagno, 1984). 

 There is strong evidence from tagging 

 data and catch records that blue sharks 

 in the North Atlantic constitute a single 

 stock (Kohler et al., 2002). Moreover, 

 mitochondrial DNA d-loop sequence and 

 nuclear microsatellite analyses indicate 

 no differences between blue sharks from 

 the eastern and western North Atlantic 

 (ShiyjiM. 



Distribution and movements of the 

 blue shark are strongly influenced 

 by seasonal variations in water tem- 

 perature, reproductive condition, and 

 availability of prey (Kohler et al., 

 2002). Blue sharks make frequent 

 trans-Atlantic movements between the 

 western and eastern regions, utilizing 

 the major North Atlantic current sys- 

 tems (Stevens, 1976, 1990; Casey, 1982, 

 1985; Kohler et al., 2002). Temporal and 

 geographic patterns of size and sexual 

 segregation have been described for this 

 species, and mating areas and pupping 

 areas are reported to be in the western 

 and eastern regions of the North Atlan- 

 tic, respectively (Casey, 1982; Kohler et 

 al., 2002). Pregnant females are rare in 

 the western North Atlantic, which is 

 dominated by juveniles of both sexes, 



adult males, and subadult females 

 (Pratt, 1979; Casey, 1982; Kohler et al., 

 2002). Catch records from the eastern 

 North Atlantic largely comprised neo- 

 nates and juveniles of both sexes and 

 adult females (Aasen, 1966; Stevens, 

 1975, 1976; Connett, 1987; Silva et al., 

 1996; Kohler et al., 2002). 



Although subjected to a number of 

 fisheries, the blue shark is primarily 

 taken as bycatch in longline fisheries 

 throughout the North Atlantic (ICCAT, 

 2002). Most blue sharks are discarded 

 or only their fins are harvested because 

 of the low palatability of their flesh 

 (Castro et al., 1999). Although incom- 

 plete, blue shark landings estimates 

 in the North Atlantic reported to the 

 International Commission for the 

 Conservation of Atlantic Tunas were 

 25.1 and 24.2 thousand metric tons (t) 

 in 1998 and 1999, respectively (ICCAT, 

 2002). Domestic longline fisheries in the 

 western North Atlantic rarely land blue 

 sharks, but it was estimated that annu- 

 al dead discards ranged from 2.8 to 29.3 

 thousand blue sharks (99.0-1136.3 t) 

 during the period 1987-2000 (Cortes, 

 2002). The major source of landings in 

 the U.S. has been the recreational fish- 

 ery, which landed 6.8 thousand blue 

 sharks in 2000 (Cortes, 2002). 



* Contribution 8 of the Massachusetts Divi- 

 sion of Marine Fisheries, P.O. Box 68, Vine- 

 yard Haven, MA 02568. 



' Shivji, M. 2002. Personal commun. 

 Nova Southeastern University, 8000 North 

 Ocean Dr., Dania Beach, FL 33004. 



