Genome-wide SNPs reveal divergence within the S. mentella complex

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Sebastes mentella (beaked redfish) represents the most commercially important species in the genus across the Northeast Atlantic. Despite increased research effort to reveal genetic structuring within the species, questions remain on precise boundaries among populations. A genome-wide survey of single nucleotide polymorphisms (SNPs) using double digested-RAD (ddRAD) sequencing revealed 2537 SNP markers, which were used to study genomic divergence within the beaked redfish. Our data suggest three genetic clusters corresponding to the ‘shallow pelagic’, and ‘deep pelagic’ morphs in addition to a ‘slope’ component. The significant neutral genomic differentiation (FST = 0.04) implies high extent of reproductive isolation between the two morphs, whereas the substantial differentiation (FST = 0.44) at 13 outlier loci may suggest adaptive radiation in S. mentella. Within the ‘deep’ group, the samples from the Faroe Islands and Irminger Sea were different from each other. Likewise, the samples from Northeast Arctic and central North Atlantic were different from each other within the ‘shallow’ group. Both the neutral and outlier SNPs support the separate management of these three groups and their sub-groups.