Researchers studied sea surface temperatures and daily fishing data from 1990 to 2023 in New Zealand's exclusive economic zone, including over 280 fish species and 39 fishing methods. They found prolonged moderate marine heatwaves were linked to increases in fish catch, but fewer fish were caught during more intense and longer heatwaves.

The authors say their work highlights how marine heatwave impacts vary around New Zealand waters, and that we need management strategies to make sure fisheries are sustainable as such heatwaves become more frequent, more intense, and longer due to climate change.

"Marine heatwaves (MHWs) are short periods of unusually warm sea temperatures that can disrupt marine ecosystems and impact fisheries. Due to climate change, these heatwaves are expected to become more frequent, longer, and more intense," says Miloud Lacheheb, PhD candidate in Economics at Victoria University of Wellington.

"In our study examining the effects of MHWs on fish catches in New Zealand's Exclusive Economic Zone, we found that moderate MHWs are linked to increased fish catches.

"However, as MHWs intensify, their impact turns negative, leading to significant reductions in fish populations and catches. This suggests that intense heatwaves severely disrupt marine habitats, posing a threat to the sustainability of fisheries," Lacheheb says.

"As MHWs continue to rise in frequency and intensity, new management strategies will be crucial to protect fisheries and marine ecosystems from further harm."

Highlights of the report include:

• Changes brought about by MHWs can reshape marine ecosystems in ways that have an economic impact on fisheries.
• MHWs are expected to become more frequent, longer, and more intense due to anthropogenic climate change.
• Moderate MHWs correlate with increased fish catches; but, as the intensity of MHWs increases, their impact becomes predominantly negative.
• Intense MHWs are associated with substantial decreases in fish catch, suggesting significant disruptions to fish populations and their habitats.
• As MHWs become more frequent and intense, better informed management approaches will be required to ensure the sustainability and viability of fisheries.

The full report can be found here.