Goldman and Musick Growth and maturity of Lamna dilropis 



283 



February and March, followed by a consis- 

 tent increase in RMI, and the largest relative 

 margins occurred in December and January. 

 There was no difference in this trend when 

 immature and mature sharks were examined 

 separately; therefore all ages classes were 

 combined (Fig. 3). 



Vertebral age-at-length data from 166 fe- 

 male salmon sharks provided von Bertalanffy 

 parameters of L^=207.4 cm PCL, it = 0.17/yr, 

 and tg = -2.3 years (Fig. 4). When the von 

 Bertalanffy growth function was fitted to the 

 quadratic-modified Dahl-Lea back-calculations 

 for females, the life history parameters were 

 similar to those produced from the sample 

 length data (Table 2). Vertebral age data from 

 16 males provided von Bertalanffy parameters 

 of L., = 182.8 cm PCL, A' = 0.23/yr, and tQ=-1.9 

 years (Fig. 4). Back-calculated lengths-at-age 

 for male salmon sharks, either with or without 

 sample data included, provided slightly lower 

 k coefficients (=0.20), but similar L^ and /,, 

 parameters (Table 2). Vertebral age data for 

 the sexes combined («=182) provided von Ber- 

 talanffy parameters of L^=204.5 cm PCL, /e = 0.18/yr , 

 and ?||=-2.2 years. A likelihood ratio test showed that 

 separate von Bertalanffy growth models describe the 

 data better for each sex than one model with the sexes 

 combined (x2=29.1; df=3; P<0.001). 



The quadratic-modified Dahl-Lea method (Eq. 3) rep- 

 resented most accurately the mean sample precaudal 



length-at-age data. It produced mean back-calculated 

 lengths-at-age within 4.2 cm of mean sample lengths- 

 at-age for female salmon sharks >120 cm PCL and 

 within 8.8 cm for females <120 cm PCL (Fig. 5A). When 

 applied to males. Equation 3 produced mean back-cal- 

 culated lengths-at-age within 10 cm of mean sample 

 lengths-at-age for sharks <120 cm PCL and >150 cm 



