About the Cougar Dam Adult Fish Collection Facility

aerial view of the adult fish collection facilityThe U. S. Army Corps of Engineers built Cougar Dam on the South Fork McKenzie River in the 1960s. Biologists estimate the habitat above the dam once supported more than 4,000 returning adult spring Chinook. Original construction included both adult and juvenile fish passage facilities to help move fish past the dam. However, due to the dam’s impact on downstream river temperatures, adult fish no longer migrated to its base. The Corps abandoned the original adult and juvenile fish passage facilities because they proved to be ineffective.

In combination with the Cougar Dam Temperature Control Facility, this new $10.4 million collection facility supports a complete fish lifecycle over long stretches of the South Fork McKenzie River by moving adult fish to high quality spawning habitat above the dam. Fisheries biologists believe this will substantially support recovery of endangered fish populations in this Willamette River sub-basin.

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The Corps’ contractor de-watered the area below the dam and installed a cofferdam immediately downstream of the construction site. Biologists rescued stranded fish in the construction area and released them into the South Fork below the cofferdam.

Construction did not require lowering the reservoir or affect recreation on the lake. Water from the reservoir flowed around the construction site through the regulating outlets so there was no interruption in the river’s flow. The Corps monitored water quality at the construction site and downstream flows in the McKenzie River.

An environmental coordinating committee addressed issues throughout the planning, design and construction of the facility. They ensured the design met current fish passage criteria and the project completed in a manner consistent with relevant environmental protection laws and regulations.
The facility includes a fish ladder leading from the base of the dam to a fish collection and sorting area. From there, adult salmon, bull trout and other resident fish are loaded onto trucks and transported to release locations above Cougar Reservoir. The facility’s design incorporates the best features of trapping facilities at other locations, including Bonneville Dam and the Cowlitz River in southern Washington.

The Corps operates and maintains the facility according to guidelines developed collaboratively between the Corps, Oregon Department of Fish and Wildlife (http://www.dfw.state.or.us/fish/CRP/) and other agencies. ODFW determines which fish species, and how many, are moved above the dam for natural spawning. ODFW biologists are on site daily conducting research and monitoring during operational months of May through October, when spring Chinook enter the South Fork McKenzie River.
While not part of the 2008 biological opinions issued by the National Marine Fisheries Service and U.S. Fish and Wildlife Service, the facility will help the Corps and other federal agencies meet requirements to prevent harmful impacts to spring Chinook salmon and bull trout listed under the Endangered Species Act.

Returns of wild adult spring Chinook salmon to the trap since it opened in 2010 have ranged between 250 and 525. We expect similar returns in the future until a long-term solution is implemented to help improve survival of juvenile salmon attempting to pass the dam on their way downstream from their spawning grounds to the ocean.