Abstract

Nassau grouper are globally critically endangered and a key fishery species in The Bahamas and parts of the Caribbean, with an urgent need for better management. Within The Bahamas, restriction-site-associated DNA sequencing (RAD-seq) and acoustic telemetry were used to establish demographic structure, diversity and connectivity, and identify the origins of Nassau grouper using an active fish spawning aggregation (FSA). RAD-seq analysis of 94 Nassau grouper sampled from nine locations generated 13,241 single nucleotide polymorphisms (SNPs). Discriminate analysis of principal components and analyses of molecular variance provided evidence in support of population sub- structuring across The Bahamas. Environmental association tests were used to explore relationships between potential loci under selection, and the gene ontology for these SNPs were identified following alignment against the available genome for red spotted grouper. Data suggest that for Nassau grouper, some environmentally-linked loci are under positive selection. Associated acoustic telemetry data suggest the likely origins of five individuals, which travelled one-way distances of up to 176 km from the FSA in the central Bahamas to two sites within the Exuma Cays Land and Sea Park - a no-take marine protected area. Analyses of high-resolution SNPs (including candidate loci under selection) revealed patterns of spatial structure and genetic connectivity not reflected by telemetry data alone. Nassau grouper from Exuma and Long Island appear to have genetic signatures that differ from other islands and from the Hail Mary FSA. Collectively, these findings provide novel information on the intraspecific population dynamics of Nassau grouper within The Bahamas.

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