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article imageSockeye salmon run and cold-water trout — The water's too warm

By Karen Graham     Aug 3, 2018 in Environment
Anywhere from five to 22 million sockeye salmon are nearing the mouth of British Columbia's Fraser River, heading home to spawn. But the waters of the river are so warm right now there is a good chance the salmon will die.
The Fraser River is the 10th longest river in Canada and has historically been considered one of the world's greatest salmon rivers. Besides its white sturgeon, which can weigh as much as 500 kilograms (1,100 lb) and measure 3.76 meters (12 ft 4 in), the Fraser has all five species of Pacific salmon (Chinook, Coho, Chum, Pink, Sockeye), as well as Steelhead Trout.
But the heatwave that has engulfed the Northern Hemisphere in a hot embrace for several weeks has raised the temperature of the Fraser and for that matter, other rivers in North America. Fisheries officials say the migrating sockeye are in danger of dying before they have a chance to spawn, reports CBC Canada.
Adult sockeye salmon encounter a waterfall on their way up river to spawn.
Adult sockeye salmon encounter a waterfall on their way up river to spawn.
Marvina Munch, U.S. Fish and Wildlife Service
Fisheries and Oceans Canada has been monitoring the water temperature of the Fraser River near Hope, B.C. every day for a number of weeks, and the average temperature has been hitting 20.7 degrees Centigrade (69.29 degrees Fahrenheit) every day for several days in a row.
"It's very warm," said Mike Lapointe, chief biologist of the Pacific Salmon Commission, who also says they are expecting as many as 14 million salmon to enter the river.
“This is the dominant run. And this is expected to be a relatively large run,” said Lapointe, who also noted that the 2018 sockeye run is part of the strongest of four life cycles for Fraser sockeye, because of the large Adams River (Shuswap Lake) population.
Actually, the past three years have seen poor salmon runs, with the 2016 sockeye run being the lowest in recorded history (a reported 853,000). “The other years weren’t anything to write home about,” said Lapointe, according to the Richmond News.
This year's sockeye run
This year's run will be the babies of the 19.8 million sockeyes that arrived in 2014. This year's run is also part of the "late summer" run, and according to Lapointe, they salmon have yet to enter the Salish Sea from the ocean. Lapointe also said about 755,000 sockeyes from all populations have been counted at the Mission checkpoint, to date, including the early spring run.
Not only is the river's water temperature too high for salmon, which will do well if the temperature is well below 17degrees Centigrade, but the streamflow in the river is also down. The water discharge is 14 percent lower than average, according to the commission.
Lush forests of the Northwest are source of oxygen  trees of Fraser Canyon  north of Hope  BC  Canad...
Lush forests of the Northwest are source of oxygen, trees of Fraser Canyon, north of Hope, BC, Canada.
Right now, Lapointe is pegging the mortality rate at about 20 percent, as long as there is no drop in the water temperature. The commission is an intergovernmental agency that works with U.S. officials as well to assess salmon populations. And in general, the warmer river temperatures are going to become an unrelenting problem.
Colorado's Fraser River in trouble too
In the U.S. state of Colorado, cold water fisheries are experiencing something close to a crisis this summer also as low stream flows and consistently high temperatures threaten the survival of trout and other sport fish across the High Country.
The problem in the high Rockies is that the fish found in these waters are cold-water fish that have evolved to live in the frigid temperatures. When the river water heats up to above 65 degrees (18.33 degrees Centigrade), there isn't enough dissolved oxygen in the water for the fish.
"At stream temperatures above 65 degrees, enough dissolved oxygen can escape into the atmosphere to stress trout," said Kirk Klancke, president of the Colorado River Headwaters chapter of Trout Unlimited. "At temperatures of 74 degrees, trout can die."
The situation is so bad in Colorado's Rocky Mountain region this summer that Colorado Parks and Wildlife has begun voluntarily closing rivers and streams to fishing, for the first time in at least two decades. The closures will affect portions of the Fraser River and Colorado River.
"We are experiencing one of the hottest, driest years in decades and with that, we are experiencing stream temperatures that are too hot for the survival of trout," said Klancke.
More about Sockeye salmon, Fraser river, warm water, prespawn mortality, Colorado
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