142 



Fishery Bulletin 94( 



1996 



lengths (males: 146-150 cm, n=728; females: 151- 

 155 cm, n=615) and attain the same maximum size 

 of 190 cm (Dudley and Cliff, 1993b). The calculated 

 L„of 193.6 cm is close to these observed maximum 

 lengths which were far greater than those reported 

 by Killam and Parsons (1983) and Branstetter 

 ( 1987a), in which males mature at less than 100 cm 

 and females at 110-120 cm, with females attaining 

 a greater maximum length than did males (Table 3). 

 Immature C. limbatus from KwaZulu-Natal grew 

 more rapidly than those from other areas. Juveniles 

 grew an average of 24 cm/yr and adolescents 11-13 

 cm/yr. Appropriate conversion of the growth rates 

 obtained by Killam and Parsons (1989) reveals ado- 

 lescent growth of 7-8 cm/yr. Branstetter (1987a) 

 found that juveniles grew 15 cm/yr, which slowed 

 down to 8 cm/yr through adolescence. While individu- 



als from the two blacktip shark populations mature 

 at similar ages, especially females, their correspond- 

 ing lengths are markedly different (Table 3). After 

 maturity, the difference in growth rates were less 

 marked: 5-6 cm/yr in our study, 4-5 cm/yr (Bran- 

 stetter, 1987a), 2-3 cm/yr (Killam and Parsons, 1989), 

 but maximum lengths showed a marked difference 

 at similar ages (Table 3). 



The differences in growth rates between the popu- 

 lations appear to be large. It is tempting to attribute 

 the differences to factors such as sample size and 

 sampling bias, preparation techniques, and reader 

 accuracy and precision (Cailliet et al., 1990). A com- 

 parison of two ring-enhancing methods revealed that 

 with the BT ageing method, the growth rate for ju- 

 venile sharks from KwaZulu-Natal was about 23 cm/ 

 yr and for adolescents 10-11 cm/yr. These values are 



