Demographics of a seasonal aggregation of white sharks at Seal Island, False Bay, South Africa
White sharks (Carcharodon carcharias) are widely distributed, ecologically important marine apex predators that are considered to be vulnerable to extinction. Given their crucial roles in structuring marine ecosystems, their populations need to be effectively monitored. Photo-identification provides a standardised, non-lethal method of assessing the population dynamics of extant species and provides live-encounter mark-recapture and data that are essential for management and conversation. White sharks occur throughout South African coastal waters but their centre of abundance is the Western Cape, where large sharks predominate at aggregation sites like Seal Island, False Bay. This study documents inter- and intra-seasonal trends in mean sighting rates and sex ratios of white sharks at Seal Island, and provides mark-recapture data that are used to estimate proportions of "resident" and "transient" white sharks, their size-distribution and maturity composition.
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