Stream reaches within the Russian River watershed in which juvenile Coho Salmon are released to assist with the recovery of this endangered fish species. The purpose is to help restore this imperiled salmon population and to protect and increase the genetic diversity of Coho Salmon in their historic range.

When released, the Coho are less than a year old and approximately two inches long. They will grow another three inches in the creek before they migrate out to the ocean. After maturing in the ocean and growing longer than two feet, the surviving adults will return to freshwater streams to spawn. Coho return to streams where they spent time as juveniles, typically completing the cycle after three years. Coho Salmon were once abundant in northern California coastal streams. The species has suffered from habitat degradation throughout its native coastal watersheds. Wildfires, floods, drought, and extreme storms have also contributed to their decline. Although studies estimate that only about 2 percent of released juveniles are likely to survive and return as adults to spawn, it is a step toward recovering a robust Coho salmon population in their native waters.

Data was derived for and published in the report: Implementation of California Coastal Salmonid Monitoring in the Russian River Watershed (2015-2019), Final Report to the California Department of Fish and Wildlife, Fisheries Restoration Grants Program, Grantee Agreement: P1430411, February 28, 2019:

https://www.sonomawater.org/media/PDF/Environment/Fisheries/reports/cmp-report-2019_ADA.pdf

Data was originally published on February 28, 2019.

Background:

Federally endangered Coho Salmon and threatened Steelhead Trout are large, charismatic fish that play crucial roles in both stream and ocean ecosystems. They transport nutrients, help keep insect populations under control, and serve as food for larger fish and mammals. They also have many known habitat requirements (e.g. cool streams with unobstructed flow, good water quality, gravel beds and plenty of large debris) that impact their survival and make them strong indicators of stream health and environmental change.

Coho Salmon and Steelhead Trout habitat are monitored in order to detect trends in the distribution and abundance of the species at key life stages in streams known to have Coho, the species of primary concern; to determine trends in fish fitness (e.g. length, weight) at key life stages; and to identify changes in Coho and Steelhead habitat.

Monitoring data helps to identify impaired habitats that hinder Coho and Steelhead recovery; guides the evaluation of stream habitat restoration and protection efforts; and assists with efforts to predict and prepare for the effects of climate change, such as changing rainfall patterns, on stream habitats and associated fish populations.

Both Coho and Steelhead populations have declined dramatically as a result of habitat loss, overfishing and changing ocean conditions. Spawning Central California Coast Coho populations are down to only about 1% of historic levels. Because the Coho have a unique life cycle where adults are normally three years old when they spawn, adults identified in a stream reach aren’t descendants of adults that were identified the previous year, or the year before that. They are offspring of adults from three years prior. This means that there are three distinct Coho “cohorts” monitored in each stream reach. Specific trends vary by cohort and by stream, but in general Coho on the West Coast are still in need of recovery actions.

For more information contact data stewards: Gregg Horton, Sonoma County Water Agency, and Mariska Obedzinski, California Sea Grant.