Wintner and Cliff: Age and growtfi determination of Carcharodon carcharias 



165 



transmitted light. The num- 

 ber of GRs counted, however, 

 were the same with these 

 two methods and for both 

 authors. While at liberty, the 

 shark's mean annual growth 

 increment was 28 cm and 42 

 kg. Francis (1996) reported 

 size at birth between 92 and 

 116 cm and weight at birth 

 between 12 and 32 kg and 

 given that this shark was 

 140 cm and 46 kg at tagging, 

 it is reasonable to assume 

 that its age was in the region 

 of one year. This estimation 

 was confirmed by the OTC 

 marker being visible at the 

 edge of the first GR (Fig. IB). 



Because we counted three 

 GRs at recapture, the mean predicted growth/GR in 

 the period from 1 to 3 GRs was 24 cm/GR and 33 kg/ 

 GR (Fig. 8). Assuming that one GR is deposited per 

 year, the total growth of shark BT433 would be 62 

 cm and 86 kg in the period of 2.6 years. If the GR 

 deposition is biannual, which is not impossible given 

 the difficulty in interpreting this vertebra (Fig. IB), 

 the mean predicted growth would be 18 cm/GR and 

 32 kg/GR; this would amount to a total growth in a 

 period of 2.6 yr (5.2 GR) of 94 cm and 166 kg. Be- 

 cause BT433 grew 69 cm and 104 kg, the first of these 

 two predictions fits the observed growth better than 

 the second. 



Further evidence to support the hypothesis of an- 

 nual GR deposition can be found in Figures 6 and 7. 

 If the number of GRs represents years, the expected 

 size and mass of shark BT433 at tagging and recap- 

 ture after 2.6 years is in accordance with the observed 

 values of our sample (Fig. 6). Assuming biannual GR 

 deposition, we believe the shark's size and mass at 

 tagging is still in accordance with the observed val- 

 ues (Fig. 7); however, it would have been in the re- 

 gion of 288 cm and 375 kg at recapture. Because evi- 

 dence of annual GR deposition in C. carcharias is based 

 on the recapture of a single shark injected with OTC 

 and because our centrum analyses neither confirmed 

 nor contradicted annual ring deposition, the discussions 

 below are based on number of GRs rather than years. 



Our VBGPs, in the absence of very large sharks, 

 were L^ = 544 cm (SE 121), k = 0.065/yr (SE 0.026), 

 and tg = -4.4 yr (SE 0.8). We fitted a von Bertalanffy 

 growth curve to the data points presented by Cailliet 

 et al. (1985) in order to compare standard errors 

 (Table 8). The results were very similar, but given 

 the larger sample size in our study, it would appear 



that there is greater variation in length at number 

 of GRs in C. carcharias from South Africa. 



Our largest shark (373 cm) measured 452 cm TL. 

 The absence of larger sharks in our study undoubt- 

 edly accounts for the lower L^ of 544 cm (686 cm TL), 

 as opposed to that of Cailliet et al. (1985) of 654 cm 

 (764 cm TL). This finding was confirmed when the 

 three markedly larger sharks (494-508 cm TL) of 

 their study were omitted and the recalculated L^ was 

 569 cm (666 cm TL) (Table 8). The conversion of the 

 original data of Cailliet et al. (1985) from TL to PCL 

 had no effect on the VBGP and their standard er- 

 rors. One should keep in mind, however, that com- 

 parisons of L^ are somewhat hampered by the fact 

 that TL length is measured in two different ways 

 (Mollet et al, 1996) by various authors, although the 

 difference in C. carcharias is not as pronounced as, 

 e.g., in members of the family Carcharhinidae. 



The maximum size attained by the white shark is 

 the subject of much interest and controversy and, 

 more importantly, uncertainty (Ellis and McCosker, 

 1991). Randall (1973, 1987) refuted the lengths of 

 1113, 900, and 640 cm TL attributed to C. carcharias. 

 According to him, the largest reliable measured white 

 shark is 513 cm (600 cm TL). Mollet et al. (1996) 

 calculated the size of two large white sharks, using 

 three morphometric measurements, at 453-701 cm 

 (530-820 cm TL) and 393-598 cm (460-700 cm TL), 

 respectively. These results were consistent with the 

 estimated TL of >700 and 700 cm, respectively. They 

 concluded that the most solid TL estimates for these 

 two sharks were those original estimates. Our L^ is 

 larger than the shark from Randall and is smaller 

 than the data of Mollet et al. ( 1996) and Cailliet et 

 al. (1985). 



