Quantifying post release mortality rates of shark bycatch in Pacific tuna longline fisheries and identifying handling practices to improve survivorship

Draft publication.

In pelagic longline fisheries shark bycatch rates are higher than in any other fishery and sharks
are typically unwanted and discarded at sea. The post-release fate of discarded sharks is largely
unobserved and could pose a large 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 release
condition and trailing gear were the two factors that had the largest effect on post release fate
where animals released in good condition without trailing gear had the best survival outcomes.