Cooperative Fish and Wildlife Research Units Program: Washington
Education, Research and Technical Assistance for Managing Our Natural Resources

Washington Project

Evaluating the relative effects of top-down and bottom-up factors on declines in Lake Sammamish kokanee salmon

June 2021 - September 2023


Participating Agencies

  • Science Applications

Historically, Lake Sammamish, Washington supported three unique runs of kokanee (Oncorhynchus nerka), which provided important food and recreational fishing opportunities for nearby communities. By the 1970s, losses of spawning habitat in tributaries to the lake and degraded water quality within the lake itself led to large declines in kokanee numbers, and by the mid-1980s the early run of kokanee had collapsed and all recreational fishing had been stopped. This project is a collaboration with scientists from Trout Unlimited; the City of Issaquah, Washington; King County, Washington; People for Puget Sound; Save Lake Sammamish; the Snoqualmie Tribe; the Wild Fish Conservancy; Washington Department of Fish and Wildlife; and the U.S. Fish and Wildlife Service. Our goal is to assess how habitat loss, fragmentation, and modification combine with direct human influences to negatively affect the viability of kokanee populations in Lake Sammamish. We will work to understand how the predator and prey communities within the Lake Sammamish Basin interact to drive changes in population dynamics of kokanee salmon. Specifically, we will focus on the top-down roles of native and nonnative predators (e.g., cutthroat trout, small- and largemouth bass) and the bottom-up influence of zooplankton and macroinvertebrate prey. This research will directly inform recovery efforts for this species of greatest conservation need and culturally valuable resource.