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Climate Change Affects Salmon,
Biologist Says

Greg Moore
Idaho Mountain Express, September 16, 2015

Migratory fish stressed by warmer water temperatures

Graphic: Adult sockeye salmon returns to Lower Granite Dam and to Redfish Lake weir on the upper Salmon River, Idaho, 1991-2013. Already at risk of extinction, wild Idaho salmon are being further stressed by warming temperatures, a fish biologist told a group of Trout Unlimited members last week.

Bert Bowler, former Columbia River policy coordinator with the Idaho Department of Fish and Game, spoke at Whiskey Jacques' in Ketchum on Sept. 9.

"Climate change is here," Bowler said.

He noted that atmospheric CO2, which traps the sun's heat, has risen from 315 parts per million in 1960 to more than 400 ppm today. He said that the last time the level was that high was at least 2.5 million years ago. Climate scientists have blamed the increase on the burning of fossil fuels.

"It took thousands and thousands of years to change," Bowler said. "Now it's changing in decades."

He said that in 2010, the earth's surface temperature was 1.35 degrees warmer than the 1950s-to-1988 average.

Bowler said 50 to 75 percent of a salmon's life is spent in the ocean. Along the western North American coast, the California Current brings cold water down from British Columbia.

"If the California Current were not there, we wouldn't have salmon in the Columbia River," Bowler said.

He said that once salmon that have left Idaho reach the Pacific Ocean, they migrate in a huge counter-clockwise circle that takes them out to the Aleutian Islands. He said water in the Bering Sea and Gulf of Alaska this summer was warmer than at any other time on record.

Bowler said a study was done of the increase in water temperatures in the lower Snake-Columbia system, which has eight dams, compared to temperatures in the Fraser River in British Columbia, which has no dams, to determine how much of the increase was due to water being slowed behind the dams and how much was due to climate change. He said the water in the lower Snake and Columbia is warmer than the water in the Fraser, but the temperatures in both are trending upward at the same rate, indicating that climate change plays a role.

That increase is being felt this summer in the Columbia and lower Snake, where warm water and low flows are killing salmon. Bowler said fish biologists estimate that more than 80 percent of the sockeye swimming upstream to spawn will die this year. He said the Department of Fish and Game trucked 51 sockeye from Lower Granite Dam, the uppermost of four dams on the lower Snake River, to the Eagle Hatchery to spawn there, and 45 made it to the Stanley Basin on their own.

Bowler said temperatures in the lower Snake River this summer reached the upper 70s -- and salmon require temperatures no higher than the lower 70s to remain healthy. He said the fish don't feed during their upstream migrations, and the warmer water accelerates depletion of their energy reserves. He said water temperatures of that level are likely to occur intermittently over the next deca de.

Bowler said an El NiƱo effect now present in the Pacific Ocean has eliminated a high-pressure ridge in the Gulf of Alaska, allowing water temperatures to become cooler.

However, he said the long-term outlook for salmon is not good, as snowpacks in the Sawtooth Mountains are melting sooner than they used to, causing lower flows and warmer water in the streams. He said adequate flow and cool water are critical for embryo survival.

More information can be found on Bowler's website,

Related Pages:
Count the Fish by Government Accounting Office, Salmon and Steelhead Recovery Efforts

Related Sites:
Idaho Department of Fish and Game Snake River Sockeye Program
NOAA Fisheries Manchester Laboratory Sockeye Program

Greg Moore
Climate Change Affects Salmon, Biologist Says
Idaho Mountain Express, September 16, 2015

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