Marine heatwaves and commercial fishing in New Zealand.

A marine heatwave (MHW) is an atypical and relatively short period of warmer Sea Surface Temperature (SST) which may be disruptive to marine life. Changes brought about by MHWs can reshape marine ecosystems in ways that have an economic impact on their users. MHWs are expected to become more frequent, longer, and more intense due to anthropogenic climate change. We leverage high-resolution SST data, and spatially and temporally detailed fish catch data, for an analysis of the impact of MHW events on fish catch in Aotearoa New Zealand's large marine Exclusive Economic Zone (EEZ). We use Geographically and Temporally Weighted Regression to assess the spatially heterogenous impact of MHWs on fish catch across different areas within the EEZ. We find that moderate MHWs correlate with increased fish catches; but, as the intensity of MHWs increase, their impact becomes predominantly negative. Intense MHWs are associated with substantial decreases in fish catch, suggesting significant disruptions to fish populations and their habitats. This pattern underscores the vulnerability of marine ecosystems and consequently commercial fisheries to the increasing frequency and severity of MHWs caused by climate change. As MHWs become more frequent and intense, better informed management approaches will be required to ensure the sustainability and viability of fisheries.