Prevalence, persistence and impacts of residual fishing hooks on tiger sharks
We used long-term observations of 55 individually identified tiger sharks (Galeocerdo cuvier) at a shark ecotourism site off Tahiti to estimate the prevalence, retention times and impacts of residual hooks and trailing line resulting from fisheries interactions. Thirty-eight percent of tiger sharks had at least one fisheries interaction resulting in retained hooks during the 8-year observation period. Both stainless-steel and corrodible hooks had a retention half-life of less than 1 year, and all corrodible hooks were shed within 2.5 years whereas firmly embedded stainless-steel hooks persisted for at least 7.6 years and are potentially retained for the lifetime of the shark. The presence of residual hooks and trailing line did not impact tiger shark growth suggesting that sharks were able to feed normally despite trailing gear. However, only a single internally-hooked sharks trailing line was observed suggesting their survival may perhaps be lower than externally-hooked individuals. Hook-retention data obtained from this study could be extrapolated to other warm water shark species that are difficult to observe in their natural habitats (e.g. oceanic whitetip shark, Carcharhinus longimanus).