Pacific salmon feed millions of people around the world each year. With numbers already drastically on the decline, rising temperatures caused by climate change now further threaten the sustainability of this vitally important fish and it remains unknown how well populations inhabiting the British Columbia coast can adapt.
A new study led by researchers at Western University provides the first evidence that a Chinook Pacific salmon has the physiological and genetic capacities to increase its thermal tolerance in response to rising temperatures. But there is a threshold to this capacity and the clock is ticking.
The findings were published as the cover story for the current issue of Nature Climate Change (https://www.nature.com/nclimate/current_issue.html).
Bryan Neff, a Western biology professor, says that climate change mitigation or other major intervention is necessary to ensure the future viability of Pacific salmon populations.
“Chinook Pacific salmon can perform aerobically in warmer environments but there is a limit,” says Neff, who also serves as the Associate Dean, Research of Western’s Faculty of Science. “We found that the demands of the Pacific salmon’s heart, at rest, exceed what its cardiac system can actually deliver at 24.5 °C, which is only four degrees warmer than the current maximum temperature they experience in the river. With these rising temperatures, the native fish population will basically experience mass heart attacks by the end of the century.”
Based on the Intergovernmental Panel on Climate Change’s average warming projection, the researchers predict a 17 per cent chance of catastrophic loss in the population by 2100 when the water temperature is expected to reach 24.5°C. This chance increases to 98 per cent in the maximum warming scenario.
“Unless we come up with climate change mitigation measures, or other interventions including physically moving these fish to an alternative cooler habitat, they’ll all be dead.” says Neff. “Now that we know this Chinook Pacific salmon can’t live in water warmer than 24.5 °C, we have a target. We can monitor the situation but without some form of intervention it doesn’t look good.”
Beyond the cultural and societal implications for Canada’s First Nations people and all Canadians, not to mention the recreational fishing industry, the continued regression of Pacific salmon populations also has a major impact on the global economy as thousands of commercial fishing jobs are being lost each year with an ever-diminishing chance of recovery.
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