Salmon and other marine life affected by recent heat waves, experts say

VANCOUVER – A sweltering heatwave 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 sockeye, coho and freshwater chinook were said to have been most affected by recent heat waves.

“They’re going to live in freshwater for one to two years and it’s this stage of the life cycle, that this particular heat wave, and the freshwater climate change in particular, is going to have some of its biggest effects.” , did he declare. 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 most significant effects, he said.

Surface waters are warmer than they have been in the past, Hinch said.

“And they stay warmer for longer due to the general increase in air temperatures associated with climate change,” he said.

“The heat waves only make it worse.”

BC salmon are already threatened 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, wiped out early runs of sockeye and Stuart chinook salmon.

The Committee on the Status of Endangered Wildlife in Canada has classified Sakinaw Sockeye Salmon, Okanagan Chinook, and some Fraser River sockeye species as Endangered. He has classified interior Fraser coho and part of 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 it can only handle the heat for so long.

The June heat wave, where the all-time Canadian temperature record was set, saw the water in the streams reach the mid-1920s, “and these are really stressful for juvenile and deadly salmon. “, did he declare.

“We start to see very bad things happen when the temperatures are 24 degrees or higher.”

There is much less oxygen in warm water and the deep water is cooler than the surface, where juvenile salmon need to feed.

Warmer temperatures also affect plankton and other small fish that salmon eat, he added.

While there is a “soft zone” that these fish typically call home in lakes during such high temperatures, he said this limits their ability to move, feed and adopt their normal behaviors.

Now that the tops of the lakes are warm, they won’t be cooling anytime soon, as brewing colder water requires strong drafts and winds that are not common in the summer months, a- he declared.

Christopher Harley, a marine biologist at the University of British Columbia, said the recent heat wave had brought temperatures above 50C on the seabed and along rocky areas along parts of the shore. Around the same time, mercury at Vancouver International Airport hit the mid-1930s.

“The rock is really 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 then you were in trouble.”

He estimates that the heat wave caused the deaths of more than a billion marine animals along the Pacific coast, including mussels, barnacles, algae and sea anemones.

“The more places I visit, the more I realize that it’s going to be a lot higher than that. It’s a growing list, ”he said of the dying marine life.

Hinch said he was most concerned about juvenile salmon in small streams that cannot take refuge in deeper areas. Their options are limited to migrating to other waters or simply dying, he said.

“We’re going to leave a much hotter and hotter world. And how the salmon will be able to adapt and maintain themselves in these conditions is still the great uncertainty. “

He said that each year brings new record high temperatures and new record water conditions.

“As we predicted 30 years ago, but we kind of see it unfolding now.”

This report by The Canadian Press was first published on July 17, 2021.