Seattle Public Utilities Mami Hara, General Manager/CEO

 

Kokanee

 

Male Kokanee

Male kokanee spawning in Webster Creek in the Cedar River Watershed.

Kokanee salmon (Oncorhynchus nerka) were discovered in Walsh Lake in the Cedar River Municipal Watershed in 1997. Kokanee are landlocked sockeye salmon that sustain their population without migrating to the ocean. Surveys documented adults in Walsh Lake, and subsequent spawning investigations revealed that kokanee were spawning in Webster Creek, a tributary to Walsh Lake. Spawning population numbers are very low in most years (< 20 redds) suggesting that relatively few kokanee reside in Walsh Lake. However, there were substantially higher numbers of kokanee and redds in 2002 through 2004 (116 to 371 redds). Walsh Lake also contains several non-native fish species including largemouth bass and yellow perch that persist in the lake since they were stocked during past decades.

A DNA analysis was conducted on kokanee samples collected while fish moved into Webster Creek to spawn. These samples were compared with other kokanee and sockeye populations in Washington State. The Walsh Lake samples had a low level of genetic diversity and a unique population structure. The low level of genetic diversity made it difficult to link this population to other populations in Washington State. Read the full report on the kokanee DNA analysis (pdf).

Read more about kokanee salmon on the Seattle Public Utilities Cedar River Biodiversity website.

Goals

Our long term goal for kokanee in the watershed is to maintain and improve the habitat in Walsh Lake and its main tributary Webster Creek, thereby providing habitat for the kokanee population to persist. Our specific objectives include:

  1. Protect water quality
  2. Restore access to spawning habitat in Webster Creek
  3. Enhance stream and riparian habitat by maintaining native vegetation and encouraging natural stream and riparian functions

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What are we doing?

Protect All Watershed Habitats
Management of the watershed is intended to avoid or minimize adverse effects of major events such as fire, spills of toxic materials, invasive species, and excessive human disturbance. In 2001, an old underground fuel tank was removed not far from Webster Creek, preventing residual fuel in the tank from potentially contaminating Webster Creek. Protecting Webster Creek and Walsh Lake from toxic spills and invasive species will likely provide the most benefit for kokanee.
View more information on habitat protection.

Stream Crossing Projects for Fish Passage
We replaced two stream crossings on Webster Creek that were barriers to fish passage and King County replaced another, further upstream within the watershed. With these barriers removed, kokanee now have access to all available spawning habitat in Webster Creek.
See more about our stream crossing projects.

Aquatic and Riparian Habitat Restoration
We stabilized the stream bank at the two stream crossing projects by planting a variety of native trees and shrubs. Riparian habitat enhancement projects include control of knotweed and removal of non-native blackberry and planting native trees and shrubs in the cleared areas. We have also planted conifer trees in areas of the Webster Creek riparian forest with few or no conifers.
View more information on our aquatic and riparian habitat restoration program.

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