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Trends in Eastern Blue Groper (Achoerodus viridis) abundance along south-eastern Australia (New South Wales): the influence of latitude, climate change and potential depth refuges.

Nathan Knott , Matthew Rees , Tom Davis , David Harasti , Hamish Malcolm, Matthew Taylor , Belinda Curley, Stephen Morris, Neville Barrett, Rick Stuart-Smith, Graham Edgar, Rachel Przeslawski

Abstract

Context. Eastern Blue Groper (Achoerodus viridis) is an iconic Australian fish and a trial prohibition of fishing for it has been implemented in New South Wales (NSW). A review of available data on this species is needed to inform future management. Aims. To assess the temporal and spatial patterns in the abundance of A. viridis. Methods. Data collected across four NSW bioregions from two systematic sampling programmes—baited remote underwater video (2010-2023) and underwater visual census (2008-2023)—were analysed with the inclusion of two other common wrasse species as references. Key results. Achoerodus viridis showed strong latitudinal variation: being least abundant in the warmer northern bioregions and peaking in abundance in the central Manning and southern Batemans bioregions. Temporal trajectories for A. viridis were mixed with significant declines on shallow reefs in the Manning and Hawkesbury bioregions, while abundances on deeper reefs were stable. Similar patterns of decline were observed for the two reference species, although both species were far more abundant than A. viridis. Conclusions. Achoerodus viridis, like other temperate wrasse, appears to be declining due to warming oceans, though depth may provide a thermal refuge. Implications. These analyses should assist decision-making for future management regulations for A. viridis.

MF24130  Accepted 18 December 2024

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