Thursday, June 30, 2011

Elwha River Bull Trout Rescue

This month, in preparation for removal of the Elwha and Glines Canyon dams, the U.S. Fish and Wildlife Service (FWS), U.S. Geological Survey, NOAA Fisheries, Washington Department of Fish and Wildlife, and the Lower Elwha Tribe participated in a multi-agency effort led by Olympic National Park to capture and relocate Elwha River bull trout from two reservoirs.

Lake Mills (formed by Glines Canyon Dam)
Removal of these large dams on the Elwha River will begin in September 2011 and is the largest dam removal project ever attempted in the United States. Although this historic dam removal will provide fish, including salmon and bull trout, access to 70 miles of pristine habitat upstream of the dams, the removal will also result in short-term water quality levels that are expected to be lethal to fish in the two reservoirs and the section of river downstream of the dams. The cause of the anticipated poor water quality is high turbidity resulting from the release of 17 million cubic yards of silt and gravel currently trapped behind the two dams and sitting at the bottom of the reservoirs where it has collected since the dams were constructed nearly 100 years ago. As a result, the FWS required Olympic National Park to develop and implement a bull trout rescue plan to move bull trout from this area during dam removal.

Helicopter lifting tote containing
40 bull trout destined for the
upper Elwha River
The rescue plan developed by Olympic National Park (and approved by FWS) called for the capture and relocation of up to 100 bull trout from the two reservoirs to locations upstream---Elkhorn and Hayes Rivers. The rescue operation collected 82 bull trout during a 10-day period using hook-and-line sampling and electrofishing techniques. We held the fish in live cages in the upper reservoir until they were flown by helicopter to the two upstream release sites on June 17. We collected a genetics sample and recorded length and weight for each fish in order to monitor how these fish respond to dam removal. We also tagged each fish to determine if the fish remain upstream where they were released or if they migrate back downstream. All 82 fish flown to the upper watershed release sites were alive and doing well at release. Detection of these fish later on will guide fish rescue recommendations for future dam removal projects in other western rivers.

For more information on this project, read the news release from Olympic National Park.