Pacific stock structure of the Silky shark (Carcharhinus falciformis) resolved with next generation sequencing

The silky shark (Carcharhinus falciformis) is subject to the second highest shark catch rates on the planet (Oliver et al. 2015) and stock assessments have found that some populations are overfished and that overfishing is still occurring (Rice and Harley 2013). Currently this species is managed as a single stock across the WCPFC jurisdiction due to a lack of information regarding stock structure. In this study, 298 silky sharks were sampled from across 5 regions of the Pacific Ocean, including off the coast of Taiwan, Papua New Guinea, the South Central Pacific, the North Central Pacific, and the Eastern Pacific. DNA sequence data included the entire mitochondrial genome as well as thousands of nuclear loci using pooled next generation sequencing. Nuclear markers yielded significant population structure between all five regions (significant FST = 0.0188 - 0.0421), and mitochondrial markers supported most of these differences (significant FST = 0.0117 - 0.0572). These analyses demonstrate multiple stocks within the WCPFC jurisdiction and provide a scientific foundation for formulating more appropriate management units for silky sharks across the Pacific.