Keywords: Species and food webs, Fishes, Freshwater habitat, Salmonids, Salish Sea Currents magazine

Scientists think they may have discovered a lost population of native kokanee salmon in Lake Washington. Salmon watchers are monitoring local creeks this fall to confirm the finding.

As a fisheries biologist with the University of Washington, Jeff Jensen was used to seeing salmon in Lake Washington and its tributaries. But in autumn 2017, he saw a type of salmon that surprised him. Jensen was at North Creek, near where he teaches at the UW’s Bothell campus, when he noticed what looked to be a run of kokanee, a variety of sockeye that does not migrate to the ocean. He knew that such fish had long been known to inhabit the lake, but he also knew that biologists considered the run to have been extirpated.

Like many species in the region, kokanee exist because of the region’s glacial history. Sockeye salmon, which migrate through Puget Sound when young and return to their natal streams to spawn as adults, periodically found their pathways to the ocean blocked by glaciers. When stuck in these lakes, the sockeye adapted to a fully freshwater life (becoming kokanee) and did not revert to their anadromous lifestyle, even after the barrier was gone.

A dead kokanee salmon with a ruler and information card in foreground.

A male kokanee salmon from the Sammamish River. Photo: Craig Barbaccia

Not only were these kokanee biologically unusual, they also tasted different. In her ethnographic study The Puyallup-Nisqually, Marian Smith wrote that the people who lived around the lake “were said to prefer this salmon [kokanee] to that which entered the rivers from the Sound.” In addition, by returning to their birth streams late in the year after the run of other salmon species, the kokanee were an important food source for Indigenous people around the lake. Early accounts by settlers and biologists also referenced the kokanee’s flavor and abundance.

The local kokanee eventually evolved three distinct groups: a late run still found in a few tributaries in Lake Sammamish and early and middle runs, both of which were thought to no longer exist. (A coalition of groups, in particular the Snoqualmie Tribe, whose people know the fish by its Lushootseed name sʔilas, or “little red fish,” are working to restore the Lake Sammamish runs.) Jensen thought that the fish he saw in 2017 could be the middle run kokanee; he also knew that fisheries biologists had made a similar observation in 2011.

Biologists are not certain about what led to the decline of kokanee but habitat loss, pollutants, and the construction of the Lake Washington Ship Canal and Locks are all thought to play a roll. Nor did the kokanee benefit from the introduction of sockeye, Chinook, and steelhead beginning in the 1920s. An additional challenge for biologists was the presence of what they called residual sockeye. The offspring of ocean-going sockeye, they spent their entire lives in fresh water, returning to the spawning grounds as kokanee look-alikes. When Jensen found his kokanee, he wondered if they were these residual sockeye, a new hybrid kokanee/hybrid, or native kokanee that escaped previous observation.

With funding from Trout Unlimited and in collaboration with the Washington Department of Fish and Wildlife Molecular Genetics lab, Jensen ran DNA tests comparing kokanee samples he collected in 2017, along with a subsequent run in 2020, with kokanee and sockeye populations from around the Pacific Northwest. The Lake Washington kokanee were most similar to, but still genetically distinct from, the native Lake Sammamish “late” run kokanee. Jensen’s mystery fish appeared to be true native Lake Washington kokanee.

(Because a small chance exists that they aren’t, Jensen hopes to run DNA tests on kokanee collected by late 19th-century University of Washington natural science professor Orson Bennett Johnson. Unfortunately, he hasn’t been able to obtain usable DNA from the fish, which Johnson collected from a small tributary of Lake Washington in November 1888 and October 1889, or about the same time of year that Jensen first saw his kokanee.)

A man bent over a metal box with water and fish inside.

Dave Kyle, Trout Unlimited, checks a remote site incubator that is used for salmon egg development. Photo: Jeffrey S. Jensen

At present, Jensen has established a network of Salmon Watchers to monitor streams in Lake Washington and lower Sammamish River tributaries. Volunteer citizen scientists select a stream, spend thirty minutes watching for salmon weekly in the fall, and send data on what they see back to Jensen. He has also teamed up with the Three Rivers Chapter of Trout Unlimited to set and monitor fry traps in the spring. To enhance kokanee production, he is planning to deploy two remote site incubators, which are enclosed habitats for salmon egg development.

"It's amazing that, after more than a century of logging, urbanization, and other onslaughts, the native kokanee have been able to hold on as a reminder of the complex ice-age history of Puget Sound and the surrounding freshwater habitats," says Jensen. His hope is that his research, the work being done by other groups, and citizen scientists can further help kokanee to continue their legacy in Lake Washington.

About the author: David B. Williams is a naturalist, author, and educator whose award-winning book Too High and Too Steep: Reshaping Seattle’s Topography explores the unprecedented engineering projects that shaped Seattle during the early part of the twentieth century. He is also the author of "Seattle Walks: Discovering History and Nature in the City," "The Street-Smart Naturalist: Field Notes from the City," and co-author of "Waterway: The Story of Seattle’s Locks and Ship Canal." His most recent book is "Homewaters: Human and Natural History in Puget Sound" published in 2021 by the University of Washington Press. You can find Williams on Twitter at @geologywriter.

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