Abstract
Nassau grouper (Epinephelus striatus) Bloch, 1792 are globally critically endangered and an important fishery species in The Commonwealth of The Bahamas (hereafter The Bahamas) and parts of the Caribbean, with an urgent need for better management and conservation. Here, we adopted a combined approach, integrating restriction-site-associated DNA sequencing (RAD-seq) and acoustic telemetry to establish country-wide demographic structure, diversity and connectivity, and the origins of Nassau grouper using an active fish spawning aggregation (FSA) in the central Bahamas. RAD-seq analysis of 94 Nassau grouper sampled from nine locations in The Bahamas generated a working dataset of 13,241 single nucleotide polymorphisms. Similar levels of genetic diversity were found among sampled locations. Evidence of population sub-structuring across The Bahamas was demonstrated and supported by discriminate analysis of principal components (DAPCs) along with analyses of molecular variance (AMOVAs). Associated acoustic telemetry data indicated Nassau grouper tagged at an active FSA in the central Bahamas during the 2016-2017 spawning season migrated to the Exumas at the conclusion of the spawning period. 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 a no-take marine protected area (MPA). Analyses of high-resolution SNP markers (including candidate loci under selection) illustrated 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 Bahamian archipelago and within an active FSA.
Highlights
25,000 of the species assessed worldwide have been classified as threatened and are at risk of extinction (IUCN, 2017), including 12% of grouper (Epinephelidae) species (Sadovy de Mitcheson et al, 2013)
Analyses of high-resolution single nucleotide polymorphisms (SNPs) markers coupled with acoustic telemetry revealed intraspecific population structure of Bahamian Nassau grouper, enabled us to determine the origins of individuals migrating to the Hail Mary fish spawning aggregation (FSA), and suggest that multiple processes influence the spatial dynamics of this species
We aimed to determine whether a genomic approach, in conjunction with acoustic telemetry, could resolve intraspecific population structure and provide additional insight into the demographics of Nassau grouper in The Bahamas
Summary
25,000 of the species assessed worldwide have been classified as threatened and are at risk of extinction (IUCN, 2017), including 12% of grouper (Epinephelidae) species (Sadovy de Mitcheson et al, 2013). Changing this trajectory will require coordinated research and management approaches to develop a more robust understanding of population demographics and ecology at both small and large spatial scales. The predictable occurrence of lunar-associated migrations to known fish spawning aggregations (FSAs) for annual reproduction with conspecifics increases their susceptibility to overexploitation (Domeier, 2012; Sadovy de Mitcheson and Erisman, 2012; Cheung et al, 2013). Many historic Nassau grouper FSAs have disappeared and others have declined by orders of magnitude in the last few decades (Olsen and LaPlace, 1979; Sadovy de Mitcheson et al, 2013)
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