Background

Willow Creek is a tributary to the lower Russian River in the estuary near Jenner in Sonoma, County. Lower Willow Creek has been subject to agricultural practices since 1850, degrading a large portion of its historic wetland habitat, including clearing of the wetlands for grazing and dredging a ditch to reroute the creek. Since California State Parks took ownership of the property in 1996, they abandoned the practice of dredging and phased out grazing operations, which led to significant regrowth of the wetland habitat. The stream channel migrated back to the southern part of the valley and six 3-foot culverts were installed to pass streamflow under the road. These culverts quickly plugged with debris, and fish were forced to swim over the road during high flows, significantly compromising fish passage.

The Willow Creek Fish Passage Project restored fish passage options for adult and juvenile coho salmon (Oncorhynchus kisutch) and steelhead (Oncorhynchus mykiss) via the construction of a 43-foot clear span bridge in 2011. Project leaders removed six debris-plugged culverts and installed a 43-foot clear-span bridge to reconnect the wetlands, reducing flooding and providing coho salmon and steelhead trout with access to seven miles of high quality spawning, rearing and winter refugia habitat. Restoring access to the Willow Creek watershed was intended to influence salmon production in the entire Russian River watershed.

Monitoring Timeline

Baseline fisheries monitoring occurred in the winter prior to construction and during the summer of construction. Fisheries monitoring has occurred on a regular basis since bridge construction in 2011.

Monitoring Purpose

A comprehensive fish monitoring program was implemented to assess the effectiveness of the installation of the new bridge to re-establish fish passage and colonization of the watershed as well as overall effectiveness of coho salmon reintroductions within the watershed and the larger Russian River basin as a result of the Russian River Coho Salmon Captive Broodstock Program.

Monitoring Methods

Spawner/red surveys in winter documented the presence of spawning salmonids to determine spatial spawning distribution within the watershed. Data collected included survey reach and team, weather conditions, stream visibility, and fish and red observations. Juvenile presence/absence survey occurred in late-July through September and documented successful spawning through the presence of rearing juvenile salmonids, density of fish, and spatial distribution in the watershed. A downstream migrant trap was installed and operated to estimate the number and migration timing of smolts migrating out of Willow Creek in the spring, and to estimate overwinter growth of juvenile hatchery coho salmon released in the fall. PIT tag antennas and transceivers were installed and operated in Willow Creek to document movement patterns, survival and abundance of PIT-tagged coho salmon released into the watershed as part of the broodstock program.

Monitoring Results

Table 1. Summary of spawning and snorkel survey observations.

Table 2. Number of individuals captured in Willow Creek downstream migrant trap during spring 2012 and 2013.

Table 3: Spawner survey counts 2011-2017

Table 4: Juvenile Presence/Absence Surveys 2012-2017

Table 5: Downstream Migrant Trap Counts 2012-2017