A sweltering heat wave across much of Western Canada during the last week of June had cascading effects on marine life, experts say.
Scott Hinch, director of the Pacific Salmon Ecology and Conservation Laboratory at the University of British Columbia, said juvenile salmon such as freshwater sockeye, coho and chinook would have been most affected. by recent heat waves.
“They’re going to live in fresh water for one to two years and it’s at this point in their life cycle, that this particular heat wave and climate change in fresh water in particular, is going to have some of its biggest effects,” he said. said in an interview.
Juvenile salmon live in freshwater for up to two years and the heat wave in this part of their life cycle has some of its biggest effects, he said.
Surface waters are warmer than they have been historically, Hinch said.
“And they stay warmer longer because of general increases in air temperature associated with climate change,” he said.
“Heat waves only make things worse.”
Salmon in British Columbia are already at risk due to a combination of factors including climate change, mining, logging, habitat loss and the Fraser River landslide.
The Fraser is one of the largest spawning rivers in the world and the landslide, discovered in 2019, decimated early runs of Stuart sockeye and chinook salmon.
The Committee on the Status of Endangered Wildlife in Canada has listed Sakinaw Sockeye Salmon, Okanagan Chinook, and some species of Fraser River Sockeye Salmon as endangered. It has classified interior Fraser coho and some Fraser sockeye as threatened and is assessing the status of chinook.
Hinch said the ideal water temperature for salmon is between 12°C and 18°C and they can only withstand the heat for so long.
The June heat wave, where the all-time Canadian temperature record was set, saw stream water reach the mid-20s, “and those are really stressful for juvenile salmon and deadly,” he said.
“We start to see some really bad things happen when temperatures are 24 degrees or higher.”
There is much less oxygen in the warm water and the deep water is colder than the surface, where juvenile salmon must feed.
Warmer temperatures also affect plankton and other small fish that salmon eat, he added.
Although there is a “sweet spot” that these fish typically call home in lakes at such high temperatures, he said it limits their ability to move, feed and engage in normal behaviors.
Now that the tops of the lakes are warm, they won’t be cooling anytime soon because mixing the cooler water requires strong air currents and winds that aren’t common in the summer months, he said. -he declares.
Christopher Harley, a marine biologist at the University of British Columbia, said the recent heat wave has resulted in temperatures above 50C on the seabed and along rocky areas along parts of the shoreline. Around the same time, the mercury at Vancouver International Airport hit the mid-30s.
“The rock is very hot and then it sends all that heat back,” Harley said.
“If you lived in the shade, if you were a mussel on the north side of a rock, you probably survived, but if you were in the sun, you were in trouble.”
He estimates that the heat wave caused the death of more than a billion marine animals along the Pacific coast, including mussels, barnacles, seaweed and sea anemones.
“The more places I visit, the more I realize it’s going to be much higher than that. It’s a list that goes on and on,” he said of the dying marine life.
Hinch said he’s most concerned about juvenile salmon in smaller streams that can’t take refuge in deeper areas. Their options are limited to migrating to other waters or simply dying, he said.
“We are going to leave a much warmer, warmer world. And how the salmon will be able to adapt and maintain themselves in these conditions is still a great uncertainty.
He said each year brings new record high temperatures and new record water conditions.
“Just like we predicted 30 years ago, but we kind of see it unfolding now.”
Hina Alam, The Canadian Press
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