Conservation project helping steelhead population
The Idaho Department of Fish and Game has seen successes with steelhead fish conservation efforts in the Clearwater River Basin since mechanical assists were installed in 2018.
The Potlatch River is home to the largest spawning area of wild steelhead in the lower basin where efforts are underway to restore habitat and enhance production of wild steelhead. The removal of passage barriers such as dams, roads and culverts allows migratory steelhead to access upstream spawning and provides juvenile rearing habitats.
One barrier was a 170-foot-long culvert on Big Meadow Creek, a tributary to the lower Potlatch River. Because of how the culvert was designed, flows were too low in the summer and too high in the spring to allow fish to move upstream. Fish upstream of the culvert were thought to have been isolated since the early 1970s, so the Idaho Department of Fish and Game modified the culvert in 2018 by installing baffles along the bottom. This slowed flows in the spring and retained water in the summer, making it possible for steelhead to access an additional 10 miles of stream habitat.
To evaluate the success of the project, fisheries biologists sampled the upstream section before and after culvert modification and collected genetic samples. The expectation was that if the culvert was no longer a barrier, anadromous adults would be able to spawn upstream of the culvert. From the juvenile fish sampled, biologists would expect that their genetic composition would become more similar to steelhead and not the resident rainbow trout.
The rapid shift in genetic composition was observed. In 2018, upstream fish shared little genetic similarity to local steelhead. But, two years after restoration, the upstream population was nearly identical to steelhead from nearby streams. This project, along with many others, aims to increase the production and resilience of steelhead populations in the Potlatch River for generations to come.
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John Hargrove is a fisheries biologist with the Idaho Department of Fish and Game.
