FISHERY BULLETIN: VOL. 87, NO. 4, 1989 



Table 1. — Size differences among juvenile blacl<tip sharks 

 with 1 , 2, or 3 vertebral rings, captured during July and August 

 1986. 



No. rings 



No. fish 



Mean TL 

 (cm) ± SD 



Mean weight 

 (kg) ± SD 



14 

 15 

 15 



68.7 ± 1.2 



93.2 ± 7.3 



111.4 ± 8.5 



2.3 

 5.8 

 8.9 



1.2 

 1.6 

 2.3 



33) and mean weight was 1.47 kg (SD = 0.28, A^ 

 = 29). These fish had prominent umbilical scars 

 which indicated recent parturition. Sharks of 

 this size possessed a birth ring on their vertebral 

 centra and were assigned to age class 0. By 

 mid-August, age sharks had increased 11.1 cm 

 (mean TL = 71.6 cm, SD = 4.74, A^ = 28), and 

 1.09 kg (mean weight = 2.56 kg, SD = 0.46, A^ = 

 28). This is an increase in length of 18.3% and an 

 increase in weight of 74.0% from mid-June to 

 mid-August. Growth during the first two 

 months was 5.56 cm and 0.55 kg/mo. Four age 

 class C. limbatus captured in early February 

 possessed two vertebral rings on then- centra 



and had a mean TL of 85.5 cm (SD = 2.3, A^ = 4). 

 Compared with the lengths of age fish in mid- 

 August, these fish had grown an additional 13.9 

 cm or approximately 2.5 cm/mo. This indicates a 

 decline in growth rates over the winter months, 

 and is depicted as a leveling off of the growth 

 curves on the length-month distribution (Fig. 5). 

 Blacktip sharks captured after May 1 that 

 possessed two vertebral rings (a birth ring and a 

 first winter ring) were assigned to age class I. In 

 late July, these fish had a mean length of 92.6 cm 

 (SD = 2.36, A^ = 13) and mean weight of 5.65 kg 

 (SD = 0.84, A^ = 14) representing gi'owth in one 

 year of approximately 21.0 cm (29.3%0 and 3.09 

 kg (120.7%). Age class II sharks (3 vertebral 

 rings) captured in late July had a mean length of 

 111.8 cm (SD = 3.51, A'^ = 15) and a mean weight 

 of 8.94 kg (SD = 0.80, A^ = 13) representing an 

 increase of 19.2 cm (20.7%) and 3.29 kg (58.2%) 

 in their second year of growth. 



Age-Length 



Growth in length was described using the von 



200- 

 180 - 



160- 



E 

 o 



X 140 



^- 



(3 



120 — 



< 



)- 

 O 



100- 



80- 



60- 



• = OBSERVED 



 = PREDICTED 



O ' BACK CALCULATED 



FEMALE 



.197(1*1.1511 



Lj' 195.0 (1-e 



r=.9874 

 n-80 



Figure 6. — Von Bertalanffy growth curve for female blacktip sharks fit from observed data. Distance between 

 ring B and ring 1 is only 7-8 months but is represented as a 1-yr interval to prevent overestimation of early 

 growth rates. 



850 



