Steelhead Trout

Steelhead in the Cedar River

The species Oncoryhnchus mykiss (O. mykiss) includes all of the various life history patterns of what are commonly referred to as rainbow trout. Previously classified in the genus Salmo, the species is now considered to be a Pacific salmon and a member of the genus Oncoryhnchus. When populations of this species express primarily an anadromous life history (spawn in freshwater, grow to maturity at sea), they are referred to as steelhead. The species also exhibits resident (remain within same river area throughout life), fluvial (migrate throughout a river network) and adfluvial (migrate between lakes and rivers) life history patterns. We will use the term rainbow trout to refer to populations expressing one or more of these non-anadromous life histories.


Both steelhead and rainbow trout are present in the Cedar River. Steelhead spawn primarily in the mainstem of the river. Rainbow trout use both the mainstem and tributaries for spawning. If they express a migratory life history, most juveniles rear in the mainstem and tributaries for one or two years prior to migrating downstream. It appears that Cedar River rainbow trout express all three non-anadromous life history patterns. Thus, the O. mykiss population in the Cedar River, comprised of steelhead and a variety of non-anadromous life history patterns, appears to display a rich level of diversity. This diversity may provide important capacity for the population to adapt to changing environmental conditions.

In recent years, the number of steelhead and rainbow trout spawning in the Cedar River has been declining. The reasons for this decline are unclear and are the subject of ongoing discussions.


Our long-term goal is to support a healthy, sustainable and diverse population of O. mykiss in the Cedar River. Our specific objectives include:

  1. Increase and rehabilitate stream habitat for O. mykiss and promote the natural ecological processes that create and maintain a healthy river system
  2. Provide sufficient amounts of high quality water to support beneficial riverine conditions in the mainstem Cedar River
  3. Provide financial support for key research and monitoring activities that provide important information for beneficial management of land and water resources in the Cedar River basin
  4. In collaboration with the Cedar River Anadromous Fish Committee and the Cedar River Instream Flow Commission, apply research and monitoring results to ongoing management practices
  5. Coordinate with and support other compatible rehabilitation activities in the Lake Washington Basin


What are we doing for O. mykiss?

Watershed Management Practices in the municipal watershed between Masonry Dam and Landsburg protect water quality, aquatic, riparian and upland habitats and the processes that create and maintain a healthy river.

Construct and operate Fish Passage Facilities at the Landsburg diversion dam to restore fish access to over 20 miles of stream habitat in the protected municipal watershed for the first time since 1901.

Instream Flow Management to promote a healthy river and provide beneficial habitat conditions for all life stages of O. mykiss.

Downstream habitat protection and restoration along the 22 miles of river below Seattle’s municipal watershed to support flood plain management practices that help create and maintain beneficial habitat conditions throughout the lower river.