Age and growth determination of the white shark, Carcharodon carcharias, from the east coast of South Africa

Ages of white sharks, Carcharodon carcharias, from the east coast of South Africa were estimated by counting growth rings (GRs) in vertebral centra an d relating them to length and mass. The vertebrae of 61 females (128-297 cm precaudal length (PCL)) and 53 males (142-373 cm PCL) were examined. Mass range was 42-442 kg for females (n = 60) and 46-882 kg for males (n = 53). X-radiography was used to enhance the visibility of the GRs in whole centra . Counts were made directly from the x-radiographs by one reader and from s canned x-radiographs by two readers. Count precision for each method and re ader was determined by using the average percentage error (APE) index which ranged from 5.3 to 6.1%. One shark injected with oxytetracycline (OTC) was recaptured after 942 days at liberty. The shark was tagged at 140 cm and 4 6 kg and grew 69 cm and 104 kg. The OTC was visible in the vertebra and the re was evidence of annual growth ring deposition. This could, however, not be confirmed with centrum analyses of the entire sample. The number of GRs counted varied in the following manner. The female and ma le with the lowest number of GRs, had 0 GR (131 cm PCL) and 1 GR (142 cm PC L), respectively. The female and male with the highest number of GRs, had 8 GRs (282 cm PCL) and 13 GRs (373 cm PCL), respectively. The smallest matur e male had 8 GRs (293 cm PCL); there were no mature females. Von Bertalanff y parameters for the combined sexes were L-infinity = 544 cm PCL, k = 0.065 /yr, t(o) = -4.4 yr. Growth calculated from predicted lengths decreased fro m 26 cm for sharks with 1 GR to 12 cm for sharks with 13 GRs. Gompertz para meters were w(0) = 54 kg, G = 3.94, g = 0.094/yr. Growth calculated from pr edicted mass increased from 23 kg (1 GR) to 94 kg (13 GRs). Back-calculated lengths and mass were lower than observed values and Lee's phenomenon was evident in both backcalculated lengths and mass but not consistently.