Salmon flood upper Clackamas River in largest run since 1958
It's been a record-breaking year for fish passage on the Clackamas River.
According to numbers from Portland General Electric, the number of adult early run coho salmon returning to the Upper Clackamas from the ocean just hit 9,000 fish, the largest seen at North Fork Dam since its construction and the start of data collection in 1958.
The fish passage work is part of the company's license with the Federal Energy Regulatory Commission (FERC), which allows them to operate hydroelectric projects on the Clackamas.
On the Clackamas River, early run coho normally pass upstream from September to October and are followed by a group of late-run fish that return from November to January.
Biologists at PGE attribute the success seen during this year's early run to infrastructure that allows fish to easily bypass dams. In 2016, a new floating surface collector was completed in the North Fork Reservoir and captures more than 90% of ocean-bound juvenile fish in the reservoir. The surface collector is the only facility in the region to move fish through a multi-dam complex using a pipeline, rather than trucking them to a release site.
Garth Wyatt, a senior fish biologist for Portland General Electric, said the fish collection rates on the Clackamas are among the highest in the region, and potentially the world.
"Using our new facilities, the time that it takes juvenile coho to pass the dams was reduced from as many as twelve days down to only two and half hours," he added.
This reduced time frame allows coho to reach the Lower Willamette River earlier in spring when temperatures are cooler and predators are less active, which increases their odds of successfully reaching the ocean. Coupled with beneficial ocean conditions, this has led to stronger adult returns and robust generations of young fish.
"We're thrilled to see our investments and science-based strategies paying off," Wyatt said.
This year's high return numbers are part of a continuing trend with fish on the Clackamas River.
"We've observed record early run coho returns in four of the last eight years, all following infrastructure improvements," Wyatt noted.
A press release from Portland General Electric noted that "early run coho now represent the largest population of wild, ocean-going salmon in the Clackamas River Basin. Biologists expect this positive trend to continue, aided by collaborative habitat restoration projects, additional fish passage improvements and ongoing scientific research in the Clackamas River Basin."
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