Simpfendorfer: Growth rates ot Larcharhinus obscurus 



815 



with OTC (111 at liberty >60 days), and 179 individuals 

 not injected with OTC ( 160 at liberty >60 days). 



Gulland and Holt (1959) method 



Linear regressions fitted to the growth rate versus aver- 

 age fork length had positive slopes for all groups exam- 

 ined. As a result estimates of K were negative, and L^ 

 was unsolvable. These results indicate that this method 

 was unable to estimate growth parameters for juvenile C. 

 obscurus. 



Fabens (1965) method 



Von Bertalanffy growth parameters estimated by the 

 Fabens (1965) method varied widely (Table 1). All the 

 groups, except the noninjected individuals, produced esti- 

 mates of A' between 0.092/year and 0.187/year, and esti- 

 mates of L . between 142 cm FL and 194 cm FL. For the 

 noninjected individuals the estimate of A was 0.031/year 

 and L^, was 379 cm FL. Values of r- for all groups were rel- 

 atively high, indicating that the von Bertalanffy param- 

 eters explained most of the variation in the data. 



Francis (1988) method 



The likelihood ratio tests for each of the five groups of C. 

 obscurus indicated that the appropriate models were rela- 

 tively simple, containing linear growth (^„=g^,), v. s. and 

 sometimes in (Table 2). Contamination probability (p) and 

 g.j were not included in the final models for any of the 



groups. The value of m was assumed to be zero for models 

 in which it was not included. 



The Francis (1988) method estimated that the linear 

 growth rate for all juvenile C. obscurus was 9.23 cm/year 

 (Table 3). The growth rate of males was 1.1 cm/year higher 

 than that for females, and 2.2 cm/year higher for OTC- 

 injected than for noninjected animals. The 95% confi- 

 dence intervals (CI), however, indicated that differences in 

 growth rate were not significant between any of the five 

 groups. Estimates of v and s were similar for all groups 

 examined, ranging from 0.24 to 0.40 and from 2.09 cm FL 

 to 2.54 cm FL, respectively. The 95% CIs indicated no sig- 

 nificant differences in v or s between groups. The values of 

 m, for models in which it was calculated, ranged from 0.69 

 cm FL to 0.94 cm FL. There were no significant differences 

 in m between the all, females, and noninjected groups. 



