278 



Abstract — Age and growth estimates 

 for salmon sharks iLamna ditropis) 

 in the eastern North Pacific were 

 derived from 182 vertebral centra 

 collected from sharks ranging in 

 length from 62.2 to 213.4 cm pre- 

 caudal length ( PCLl and compared to 

 previously published age and growth 

 data for salmon sharks in the western 

 North Pacific. Eastern North Pacific 

 female and male salmon sharks were 

 aged up to 20 and 17 years, respec- 

 tively. Relative marginal increment 

 (RMI) analysis showed that postnatal 

 rings form annually between January 

 and March. Von Bertalanffy growth 

 parameters derived from vertebral 

 length-at-age data are L^ =207.4 cm 

 PCL, /; = 0.17/yr, and ?o=-2.3 years for 

 females (;7 = 166), and L,=182.8 cm 

 PCL, k = 0.2ZlyT , and tf, = -1.9 years 

 for males {n = 16}. Age at maturity 

 was estimated to range from six to 

 nine years for females (median pre- 

 caudal length of 164.7 cm PCLi and 

 from three to five years old for males 

 (median precaudal length of 124.0 cm 

 PCLl. Weight-length relationships for 

 females and males in the eastern 

 North Pacific are W=8.2x 10-05xL2 759 

 (r-' = 0.99) and W=3.2x IQ-"** xL^ ^^^ 

 (r-=0.99), respectively. Our results 

 show that female and male salmon 

 sharks in the eastern North Pacific 

 possess a faster growth rate, reach 

 sexual maturity earlier, and attain 

 greater weight-at-length than their 

 same-sex counterparts living in the 

 western North Pacific. 



Growth and maturity of salmon sharks 

 iLamna ditropis) in the eastern and 

 western North Pacific, and comments 

 on back-calculation methods 



Kenneth J. Goldman 



Alaska Department of Fish and Game 



3298 Douglas Place 



Homer, Alaska 99603 



E-mail address: ken_goldmanm'fishgame. state. ak. us 



John A. Musick 



College of William & Mary. School of Marine Science 

 Virginia Institute of Marine Science 

 Route 1208, Create Road 

 Gloucester Point, Virginia 23062 



Manuscript submitted 23 October 2003 

 to the Scientific Editor's Office. 



Manuscript approved for publication 



15 September 2005 by the Scientific Editor. 



Fish. Bull. 104:278-292 (2006). 



The salmon shark (Lamna ditropis) 

 is a large apex predator inhabiting 

 the coastal and oceanic waters of the 

 North Pacific Ocean, most commonly 

 ranging from 65°N latitude to 35°N 

 in the west and to 30^N in the east 

 (Strasburg, 1958; Neave and Hana- 

 van, 1960; Compagno, 1984, 2001; 

 Blagoderov, 1994; Nagasawa, 1998). 

 It is found individually and in large 

 aggregations at sea-surface tempera- 

 tures of 5°C to 18°C and has a depth 

 distribution ranging from the surface 

 to at least 150 m (Compagno, 1984, 

 2001). The salmon shark is a highly 

 opportunistic predator, feeding on a 

 wide variety of prey and sharing the 

 highest trophic level of the food web 

 in boreal and temperate North Pacific 

 waters with marine mammals and 

 seabirds (Brodeur, 1988; Nagasawa, 

 1998). Adult salmon sharks typically 

 range in size from 180-210 cm precau- 

 dal length (PCL; = 200-260 cm total 

 length, TL) and can weigh up to 220 kg 

 (Tanaka, 1980; JAMARC, 1980; Naga- 

 sawa, 1998). Reported lengths of 300 

 cm TL and greater and weights exceed- 

 ing 450 kg are unsubstantiated. 



Salmon sharks are migratory in 

 nature. North-south migrations have 

 been documented on both sides of the 

 North Pacific; northern movements 

 occur in spring and southern move- 



ments are occur in autumn (lino, 

 1939; Kosugi and Tsuchisaki, 1950; 

 Gorbatenko and Cheblukova, 1990; 

 Balgaderov, 1994; Nakano and Na- 

 gasawa, 1994). However, this species 

 is present in boreal waters through- 

 out the year (Goldman and Human, 

 in press; Weng et al., 2005). Salmon 

 sharks tagged with satellite transmit- 

 ters have shown an extremely wide 

 range of movements throughout the 

 eastern North Pacific — movement as 

 far south as southern California and 

 Hawaii (Weng et al., 2005). To date, 

 however, no salmon shark has been 

 recorded moving across the Pacific, 

 but such movements are suspected to 

 occur (Nakano and Nagasawa 1996; 

 Goldman and Musick, in press; Weng 

 et al., 2005) 



Sexual segregation is relatively 

 common in sharks; however an ex- 

 tremely large sex ratio difference 

 exists in salmon sharks across the 

 North Pacific basin (Sano, 1962; Na- 

 gasawa. 1998; Goldman and Musick, 

 in press). The western North Pa- 

 cific (WNP) is male dominated and 

 the eastern North Pacific (ENP) is 

 female dominated. Male dominance 

 in the WNP and female dominance 

 in the ENP increase with increasing 

 latitude. Larger sharks range farther 

 north than smaller individuals, and 



