Abstract
Age and growth of Carcharhinus obscurus was studied by vertebral ageing techniques. The annual formation of growth bands in the vertebrae was validated with oxytetracycline-injected individuals at liberty up to 1481 days. Growth-band counts of vertebral samples from 305 individuals ranging in size from 63 to 282 cm fork length were used to construct growth curves. Assuming a mean size at birth of 75.3 cm, estimates of von Bertalanffy growth parameters for males were: L∞ = 336.5 cm and K = 0.045 year–1. Growth parameters for females were: L∞= 354.4 cm and K = 0.043 year–1. The age at maturity was estimated to be 17–22 years for females (220–250 cm), and 20 – 23 years for males (230–243 cm). The oldest animal aged was a 32-year-old female 274 cm in length. Growth-rate estimates based on vertebral ageing for animals up to 5 years of age are similar to those from tag–recapture studies on the same population. The results of the present study were similar to those for C. obscurus from the south-western Indian Ocean and the western North Atlantic Ocean, indicating that age and growth are similar among these populations.
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