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

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 programs, namely, baited remote underwater video (2010–23) and underwater visual census (2008–23), 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 bioregion 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, whereas 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 was A. viridis. Conclusions Achoerodus viridis, like other temperate wrasse, appears to be declining because of warming oceans, although depth may provide a thermal refuge Implications These analyses should assist decision-making for future management regulations for A. viridis.