Marine heatwaves are causing fish populations to decline and migrate to new habitats at rates up to four times faster than the impacts linked to long-term ocean warming, according to new scientific findings that are raising concerns over the future of global fisheries.
Published in the recent the Food and Agriculture Organization of the United Nations (FAO) and the World Meteorological Organization (WMO) report on Extreme Heat and Agriculture , marine heatwaves are intensifying climate-related disruptions in oceans and creating severe challenges for fisheries management and food security.
Marine heatwaves are prolonged periods of unusually high ocean temperatures that can last for weeks, months, or even years. Scientists say these events have become more frequent and intense due to climate change.
Researchers examining fisheries in the northeast Pacific reported that marine heatwaves can trigger rapid biomass declines and major shifts in fish distribution far faster than gradual warming trends projected over decades.
According to the study, fish stocks exposed to marine heatwaves experienced changes in biomass and geographic distribution “at least four times faster and bigger in magnitude” than those associated with long-term climate warming.
The findings suggest that current fisheries assessments may underestimate the full impact of climate change because many projections focus primarily on gradual warming while overlooking short-term but extreme heat events.
Scientists warned that marine heatwaves could double climate-related impacts on key fisheries species by 2050 compared to earlier assessments that only considered long-term warming patterns.
Recent research published in the journal Nature Ecology & Evolution further showed that long-term ocean warming is already driving significant declines in fish biomass. The study analyzed more than 702,000 biomass estimates across nearly 34,000 fish populations between 1993 and 2021.
Researchers found that chronic warming was linked to annual biomass declines of up to 19.8 percent in some fish populations. At the same time, marine heatwaves and warmer years caused sharp losses of up to 43.4 percent in populations living at the warm edge of their habitats.
However, some fish populations in colder regions temporarily benefited from warmer conditions, recording biomass increases of up to 176 percent as species shifted toward cooler waters. Scientists cautioned that these short-term gains could create a false impression of recovery and lead to overfishing if not carefully managed.
Marine heatwaves are also reshaping marine ecosystems by forcing species to move toward the poles or deeper waters in search of cooler conditions. A report by NOAA Fisheries noted that marine heatwaves can shift ocean temperatures hundreds of kilometers within months, disrupting habitats and food chains.
Environmental experts say the growing frequency of marine heatwaves poses serious risks to biodiversity, coastal livelihoods, and global seafood supplies. The International Union for Conservation of Nature (IUCN) estimates that marine heatwaves have increased by 50 percent over the past decade and could become up to 50 times more frequent by the end of the century if greenhouse gas emissions continue rising.
Scientists are now calling for climate-smart fisheries management strategies that account for both long-term warming and extreme marine heat events to protect vulnerable fish stocks and sustain marine ecosystems.
