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Fisheries biologists from Olympic National Park and partner agencies completed elements of the park’s Bull Trout Protection and Restoration Plan June 17.
Scientists used both hook-and-line and electrofishing sampling techniques to capture 82 juvenile and adult bull trout over the course of ten days, working in the vicinity of Lake Mills and the middle Elwha River in Olympic National Park.
The fish were held in live pens in Lake Mills until June 17, when the fish were relocated via four helicopter flights to two upstream locations, near Elkhorn Ranger Station and at the mouth of the Hayes River. Prior to their release back into the upper river, the fish were genetically sampled and measured. Captured fish averaged 14 inches in length, with some fish measuring up to 24 inches. Thirty-one of the fish were fitted with radio transmitters, which will allow fisheries managers to track the relative success of moving fish into the upper Elwha Valley.
Beginning in mid-September, contractors will begin to remove the Elwha and Glines Canyon Dams. As dam removal begins and the Lake Aldwell and Lake Mills reservoirs drain, the river will begin to erode large amounts of sediment that has accumulated in the reservoirs since dam construction. The Bureau of Reclamation estimates more than 24 million cubic yards of sediment is now stored in the reservoirs, a majority (20.3 million cubic yards) as a delta at the south end of Lake Mills. High levels of sediment in the lower river would have an adverse and potentially lethal effect on fish.
With the Lake Mills reservoir recognized as a stronghold for bull trout in the Elwha River system, implementation of the plan fulfills a requirement outlined in a 2000 revision to the 1996 U.S. Fish and Wildlife Service Biological Opinion on the Elwha River Restoration project. Bull trout (Salvelinus confluentus) were first listed as a threatened species under the Endangered Species Act in 1999.
“Using the best available science, we’ve taken steps to protect the bull trout population and given them immediate access to high-quality, pristine habitats in the upper river through this relocation project,” Olympic National Park fisheries biologist Sam Brenkman said.
Over the last five years, fisheries biologists have conducted a number of key studies in order to protect bull trout during dam removal. These efforts include the tracking of fish via radio telemetry, two headwaters-to-mouth (45-mile) snorkel surveys and genetic studies.
Based on this work, the adult bull trout population is estimated to be less than 400 fish. Riverscape snorkel surveys conducted in 2007 and 2008 indicate that bull trout represent approximately three percent of the entire Elwha River fish community. Between 60 – 69 percent of the observed bull trout occur from Rica Canyon downstream, which includes Lake Mills.
“We are pleased that we met our objectives, and this project, designed to protect a threatened species, would not have been possible without close collaboration among the various agencies,” Olympic National Park fisheries biologist Pat Crain said. “During two weeks of field work, more than 20 biologists—from the U.S. Fish and Wildlife Service, U.S. Geological Survey, National Oceanic and Atmospheric Administration, Lower Elwha Klallam Tribe, Washington Department of Fish and Wildlife, and Student Conservation Association—assisted with and monitored the capture and relocation effort.”
In addition to the upriver relocation, Olympic National Park has undertaken additional means to protect bull trout and remove barriers to fish migration. Last year, an undersized, fish-blocking culvert on Griff Creek was replaced with a 26-foot bottomless culvert that will allow bull trout and other migratory fish species access to this important middle river tributary. Fisheries biologists at the park are also engaged in an extensive evaluation of non-native brook trout in the watershed, as they are known to compete with and sometimes interbreed with bull trout.
For more information on the life history and population distribution of bull trout in the Elwha River, please visit www.nps.gov/olym/naturescience/bull-trout.htm. To read the Bull Trout Protection and Restoration Plan, see www.nps.gov/olym/naturescience/elwha-restoration-docs.htm.
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