Redwood Creek is a 19.4 square km (7.5 square mile) coastal watershed in southern Marin County, California. Redwood Creek flows southwest from the flanks of Mt. Tamalpais, through Muir Woods National Monument (MUWO), discharging to the Pacific Ocean through Big Lagoon at Muir Beach. Protected from development, the watershed is primarily contained within the boundaries of Mt. Tamalpais State Park, Golden Gate National Recreation Area, and MUWO. The watershed provides habitat to three federally protected species (coho salmon – endangered; steelhead – threatened; and the California red-legged frog – threatened). According to the National Marine Fisheries Service Genetics Laboratory, the coho salmon found in Redwood Creek represent a genetic outlier within the CCCESU with extreme genetic distance from all other samples collected within the CCCESU and the Southern Oregon-Northern California Coast Evolutionarily Significant Unit (Bjorkstedt et al. 2005).
The National Park Service San Francisco Bay Area Network Inventory and Monitoring Program and California Department of Fish and Wildlife have supported monitoring of multiple coho salmon life stages in coastal Marin County watersheds since 1998. Monitoring includes:
adult escapement surveys
, which document the number of adult salmonids that successfully "escape" ocean fisheries and return to their natal streams to spawn, as well as the number of redds (gravel nests where salmonids lay their eggs) created; and
outmigrant smolt trapping
, where the number of smolts (at least year-old juvenile salmonids that have undergone changes to cope with a marine environment) are captured, measured and counted as they make their way toward the ocean; and
basinwide juvenile coho surveys
and summer index reach monitoring
which seek to quantify the number of juvenile salmonids present in the watersheds during the summer months.
Coho salmon redd numbers in the Redwood Creek watershed by cohort winter 1997-1998 through winter 2012-2013.