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Chinook and sockeye passing through fish ladder

Chinook and sockeye in the Landsburg Dam fish ladder and sorting facility.

Six of the 14 species of greatest concern listed in the HCP are fish. Three of these species, Chinook salmon, bull trout, and steelhead trout, are listed as threatened under the Federal Endangered Species Act. Four other fish species are considered species of concern in the HCP.

Creating access to high quality habitat

From 1901 to 2002, the Landsburg Dam blocked the upstream passage of all fish. As one of the first projects carried out under the HCP, Seattle constructed and now operates fish passage facilities at the Landsburg Diversion Dam. This allows Chinook, coho, steelhead, adfluvial and resident trout, and other native species to pass upstream into 21 miles of formerly unoccupied mainstem and tributary streams in the protected municipal watershed. This gives these fish 34.5 miles of spawning habitat, from the mouth at Lake Washington in Renton to the natural barrier at Cedar Falls. The process of these fish species recolonizing habitat above the dam is being monitored and evaluated in a collaborative investigation conducted by scientists from SPU, University of Washington, and NOAA Fisheries. Read more about the salmon recolonization study on the Seattle Public Utilities Biodiversity website.

Special help for sockeye

Due to their much greater abundance and potential effect on drinking water quality, sockeye salmon are not allowed to pass upstream of Landsburg Dam. To address sockeye conservation, SPU funded the construction and operation of a new, state-of-the-art hatchery.

Protecting the amount of water for the life stages of fish

The HCP provides a guaranteed instream flow regime composed of minimum and supplemental flows to help ensure beneficial base flow conditions for all fish species throughout the year. This regime is particularly targeted to the needs of all life stages of Chinook, sockeye, and coho salmon and steelhead trout.

Within the municipal watershed there is a population of kokanee (landlocked sockeye salmon) that reside in Walsh Lake and spawn in its tributary, Webster Creek. Upstream of the Masonry Dam, bull trout and pygmy whitefish use the Chester Morse Lake reservoir complex and associated tributary streams and rivers at various points in their life history. Bull trout use stream habitat for rearing and spawning before migrating to the reservoir where the vast majority of the population utilizes habitat for most of the year. Pygmy whitefish spawn in major river systems but primarily reside in the main reservoir throughout their lives.

Reservoir operations cause fluctuations in water elevations that alter available habitat in the reservoir and lower reaches of river habitat. Several projects under the HCP helped us better understand the impacts of water operations on the ecology of these important fish species. Other projects restored and protected important stream habitat in the upper watershed.