Population genetic structure of Indo-West Pacific carcharhinid sharks: what do we know and where to from here?

Abstract

The Carcharhinidae is one of the most at-risk shark families in the Indo-West Pacific (IWP), which is a global priority for the conservation of elasmobranchs. Of the 57 described species of carcharhinids, 43 are known from the IWP, where many are subject to high fishing pressure. Many of these species are also found outside this bioregion. Understanding the connectivity of individual species across their ranges is paramount to successful management of their fisheries. Studies of population genetic structure have been the mainstay for assessing connectivity. Here, we review 41 studies pertaining to the population genetic structure of 20 species of carcharhinid whose ranges include the IWP and for which relevant data are available. The genetic markers used range from microsatellite loci and small mitochondrial DNA sequences (375 to 4797bp) to genomic analyses. Overall, the population genetic structure for these carcharhinids was varied but patterns emerged according to the lifestyle of the species, with the greatest structure shown by species that are highly habitat dependent and the least structure shown by oceanic species. Experimental designs of the underlying studies have, however, often been opportunistic with small sample sizes, few locations sampled and based on analysis of single mitochondrial regions and/or few microsatellite markers. The literature provides a basis for understanding the population genetic structure of IWP carcharhinids, but future research needs to focus on the application of population genomics and more robust experimental design so that population genetic structure can be quantified with higher certainty and resolution over finer spatial scales.