The Blue Grenadier (Macruronus novaezelandiae) is one of the most valuable demersal finfish in Australia’s Southern and Eastern Scalefish and Shark Fishery (SESSF), with annual landings regularly exceeding 10,000 tonnes. Effective management of this resource is currently based on the Australian population comprising a single and well-mixed biological unit. From a genetic perspective, a single allozyme study in 1987, that examined ten polymorphic protein loci, supports this management approach. The allozyme study, however, lacked the resolution to detect subtle genetic differentiation often present in high-gene-flow marine fishes. Blue grenadier larval distribution surveys and otolith chemistry have since suggested the possible existence of a second, independent spawning aggregation in eastern Bass Strait, raising questions on the stock structure of blue grenadier in Australian waters. This uncertainty required evaluation using contemporary genomic markers, as misalignment between management units and population structure can lead to the localised depletion of distinct spawning components, with consequences for long-term sustainability.
This study applied double-digest restriction site-associated DNA sequencing (DArTseq) provided by Diversity Arrays) generating thousands of genome-wide SNPs from over 176 blue grenadier individuals sampled across multiple Australian locations, including from recognized and putative spawning regions. Principal component analysis, Bayesian clustering and pairwise analyses of genetic differentiation, enabled testing of population structure within the SESSF. The findings of this study provided updated insights into the species’ genomic population structure, delivering the first genome-wide SNP assessment of the species in Australian waters and contributing data informing the assessment and management of Australian M. novezelandiae stocks.