Age and growth estimates for the Zambezi shark, Carcharhinus leucas, from the east coast of South Africa

Abstract

Growth rings (GR) were counted in vertebrae of 69 female (56–221 cm precaudal length; 3–238 kg) and 54 male (57–216 cm; 3–180 kg) C. leucas. Annual GR deposition could not be confirmed by centrum edge analyses but was assumed on the basis of ‘mark–recapture’ analysis of 10 sharks held captive for between 2.2 and 20 years in an aquarium. GR counts indicated that the largest female and male were 32 years (221 cm) and 29 years (216 cm), respectively and the smallest mature female and male were 14 years (197 cm) and 25 years (196 cm). Length at 50% maturity was 193 cm (21 years) and 190 cm (20 years) for females and males, respectively. Maximum age is >50 years, and the two specimens (216, 217 cm) that have been held in the aquarium for 20 years are both estimated to be >29 years. Von Bertalanffy parameters for the combined sexes were L_∞ = 230 cm, k = 0.071 year^–1, t₀ = –5.12 years, and Gompertz parameters were w₀ = 24 kg, G = 2.86, g = 0.046 year^–1.