Genome-wide evaluation of Scylla serrata (giant mud crab) population structure between and within two continental shelf regions of northern Australia

Context: Offshore spawning and larval distribution of the wide ranging Scylla serrata (giant mud crab) provides genetic connectivity potential across large spatial scales. Aims: We examined the genetic connectivity of S. serrata between and within two large continental shelves of northern and eastern Australia, to inform fisheries assessment and management. Methods: Over 300 individuals were sampled from 14 locations, within 6 oceanographic regions, across the 2 continental shelves, providing 40,364 single nucleotide polymorphisms (SNPs) for analysis. Key results: Results indicated a single genetic stock along the eastern continental shelf of Australia with no evidence of north to south structuring. A separate genetic stock on the northern continental shelf of Australia was indicated, with evidence supporting a degree of east–west structuring of S. serrata populations within the Gulf of Carpentaria. Conclusions: The spatial extent of genetically connected S. serrata metapopulations is likely dependent on the oceanographic features of a region. The spatial scale of S. serrata stocks should be assessed on a case-by-case basis, confirmed by empirical evidence (e.g. SNP analysis) given connectivity is likely dependent on regional oceanographic conditions. Implications: The outcomes of this study have implications for management of fished S. serrata stocks, especially where fishing mortality may (or may not) have effects beyond the jurisdiction of interest.