The Army Corps of Engineers is investigating whether the start-up of Dworshak Dam’s turbines are responsible for the deaths of around 30 steelhead, according to a press release from the Army Corps.
The U.S. Army Corps of Engineers found the dead fish in late December after Idaho Fish and Game reported sightings of numerous dead steelhead on the North Fork of the Clearwater River, which joins the Snake River near the Idaho-Washington border.
After a preliminary investigation, according to the Army Corps, operators followed all turbine start-up procedures, including the use of compressed air to help lower the water level below the turbine blades.
The goal of these procedures is to greatly reduce fish mortalities. However, there are still risks to fish, according to the Army Corps.
In 2016, around 200 steelhead were found dead at Dworshak Dam. At the time, the Army Corps said a non-routine upgrade to one of the turbines appeared to have injured the fish.
The Army Corps did not respond to questions about the incident by deadline.
The steelhead deaths come after record low returns of steelhead to the Columbia River this past summer, according to a report from OPB.
Steelhead are large trout that migrate out to the ocean and return to the freshwater to spawn. If the fish do not migrate out to the ocean, they’re known as rainbow trout. Steelhead on the Columbia and Snake rivers are listed as threatened on the federal Endangered Species List.
