Salmon recovery after Elwha dam removal
Joining a collaborative team of scientists, researchers are investigating a wide range of ecosystems and salmonid populations in the newly reopened Elwha river system, documenting the “before” needed to understand the “after” that will follow two historic dam removals.
Thomas Quinn, University of Washington, School of Aquatic and Fishery Sciences
Joseph Anderson, Washington Department of Fish and Wildlife
Michael McHenry, Lower Elwha Klallam Tribe
George Pess, NOAA/NMFS Northwest Region
Mara Zimmerman, Washington Department of Fish and Wildlife
Washington Sea Grant-supported researchers have joined a collaborative team of scientists from across state and local agencies, tribes, and universities to gather extensive physiological, microchemical, isotopic, behavioral, and reproductive data on this complex ecosystem’s numerous salmon and trout species. They also gathered vital baseline data over multiple years on limnology, chemistry, temperatures, stream flows, oxygen levels, stream flow, and plankton production in Lake Sutherland and its outlet— Indian Creek—above the old dams, and in the estuary downstream.
Washington Sea Grant-supported researchers have met this challenge since 2012, chronicling the Elwha ecosystem’s transformation by measuring fish numbers, movements, redds (spawning nests), genetics, body and egg size, and stable-isotope composition.
The team made several important findings in 2015. They determined how to distinguish redds made by steelhead and rainbow trout and thus determine whether sympatric breed occurs. They found that summer-run steelhead have much more fat than winter-run. Wild and hatchery-origin steelhead also differ in fat level, and isotopes revealed they feed differently in the ocean. Kokanee in upriver Lake Sullivan descended from pre-dam anadromous sockeye rather than coming from elsewhere. Despite fears that nonnative brook trout might suppress returning coho salmon, the coho seem to be competing successfully.
Quinn, TP, Harris N, Shaffer JA, Byrnes C, Crain P (2013) Juvenile coho salmon in the Elwha River Estuary prior to dam removal: seasonal occupancy, size distribution, and comparison to nearby Salt Creek. Transactions of the American Fisheries Society, 142(4):1058-1066.
Quinn TP, Shaffer JA, Brown J, Harris N, Byrnes C, Crain P (2013) Juvenile Chinook salmon, Oncorhynchus tshawytscha, use of the Elwha river estuary prior to dam removal. Environmental Biology of Fishes, 97(6):731-740.