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VIDEO: Chinook Salmon Also Suffered from Hot Idaho Summer

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Idaho Fish and Game trapped more than 50 sockeye salmon from the Snake River this summer to save them from hot temperatures. Chinook salmon also suffered. - JESSICA MURRI
  • Jessica Murri
  • Idaho Fish and Game trapped more than 50 sockeye salmon from the Snake River this summer to save them from hot temperatures. Chinook salmon also suffered.
Earlier this summer, fish biologists expressed alarm as the Pacific Northwest sockeye salmon population tanked. The hottest summer on record for the Pacific Northwest brought temperatures of river water up to nearly 80 degrees—fatal for most salmon. Between 50 and 90 percent of the migrating sockeye salmon were expected to die this season.

The Idaho Department of Fish and Game quickly launched an effort to save the sockeyes—which are considered endangered in Idaho. They trapped 51 adult sockeyes at the Lower Granite Dam on the Snake River and trucked them eight-and-a-half hours to the Eagle Fish Hatchery, where they could wait until temperatures cooled in the fall to be released into their spawning grounds at Redfish Lake.

According to a news release from IDFG, sockeyes weren't the only salmon species to take a hit from the warmer temperatures. Chinook salmon also struggled to stay alive.

"Because of the water temperatures in the South Fork being in the upper 70s, we were seeing a lot of mortality over there with fish that we were holding as well as fish that were in the river swimming free," said McCall Hatchery Assistant Manager Joel Patterson in the news release. "So, those fish were then transported here because of elevated temperatures and low flows."

To accommodate the influx of Chinooks, the hatchery had to move some fish around. Normally, it houses catchable rainbow trout in the summer, but hatchery workers moved those fish to lower elevation lakes and streams early to make room for the salmon. 

Usually the salmon would spawn in the fish trap on the South Fork of the Salmon River were collected and spawned at the McCall Hatchery in late August and early September. IDFG put together a video showing the process of Chinook spawning at the hatchery—not quite as peaceful and natural as the process might be in the river.

On the sockeye side of things, a total of 45 sockeye salmon survived the 900-mile journey from the ocean to the Sawtooth Basin, out of 400 that passed the Lower Granite Dam earlier this summer. Fish and Game release another 650 adults from the captive broodstock program at the Eagle Fish Hatchery into the lake to spawn this month.