Quantifying post release mortality rates of sharks incidentally captured in Pacific tuna longline fisheries and identifying handling practices to improve survivorship

Shark bycatch rates are higher in pelagic longline fisheries than in any other fishery, and these sharks are typically discarded at sea. The post-release fate of discarded sharks is largely unobserved and could pose a significant source of unquantified mortality. This study assessed post release mortality rates of blue (Prionace glauca), bigeye thresher (Alopias superciliosus), oceanic whitetip (Carcharhinus longimanus), and silky (C. falciformis) sharks discarded in two tuna target fisheries in the western and central Pacific Ocean. The study found, that the condition at release (good versus injured) and the amount trailing gear left on the animals were the two factors that had the largest effect on post release fate. Animals released in good condition without trailing gear had the highest rates of survival. 2019 NMFS (National Marine Fisheries Service) PIFSC (Pacific Islands Fisheries Science Center) Submitted https://doi.org/10.25923/2sxy-s659 Public Domain 1862