Relative contribution to the shark fin trade of Indo‐Pacific and Eastern Pacific pelagic thresher sharks

Abstract Fins from highly mobile shark species entering large shark fin trade hubs can originate from various geographical locations and stocks. Tracing fins from internationally regulated species to their starting point in the supply chain can have important implications for the monitoring and enforcement of international laws intended to protect threatened shark species. Here we use pelagic thresher shark Alopias pelagicus fin samples ( N = 86) collected during a 4‐year period (2014–2017), and phylogenetic analyses, using the cytochrome oxidase I (COI), to determine the relative contribution of this species to the two largest shark fin trade hubs in the world, Hong Kong and Guangzhou, mainland China. Our results suggest that the Eastern Pacific is a major starting point of the international supply chain of pelagic thresher shark fins, contributing 84.9% of the analyzed market‐derived fin samples. We suggest that capacity building investments are needed in Eastern Pacific countries to increase the efficiency of border control inspections and improve the enforcement of international trade regulations for this threatened shark species. Our study highlights the utility of combining population genetics data and large‐scale market surveys to trace wildlife products back to the starting point in the supply chain and support the assessment of emerging management and conservation measures for exploited sharks.