Coho Salmon (Oncorhynchus kisutch) in Pine Gulch Creek, Marin County, CA. 2002 Monitoring Report

Ketcham, B.; Brown., G.

Pine Gulch Creek drains a 19.8 square kilometer perennial watershed in coastal Marin County, California, and is the primary freshwater input to Bolinas Lagoon. The watershed supports a population of steelhead (Oncorhynchus mykiss) and it is generally accepted that it supported a native self-sustaining population of coho salmon (O. kisutch) into the 1970’s. Following thirty years without documented coho sightings, recent National Park Service (NPS) monitoring activities have detected the presence of three consecutive cohort year classes in Pine Gulch Creek. This report includes monitoring results from adult spawner surveys, outmigrant smolt trapping, and a modified Hankin-Reeves coho juvenile population estimate for this newly returned population. Beginning in winter 2000-2001, coho salmon spawners have been observed in low numbers (<5 per year) within the watershed. Modified Hankin-Reeves surveys yielded estimates of 589 (± 329) juvenile coho salmon in September 2001 and 1205 (± 337) juvenile coho salmon in September 2002. The 2002 survey results indicate higher abundance and wider distribution of coho than the 2001 survey. In response to juvenile presence in 2001, a smolt trap was operated in the spring of 2002 capturing 249 coho smolts. Evaluation of genetic samples indicate that coho salmon captured during summer 2001 in Pine Gulch Creek have a strong genetic affinity to coho in the Redwood Creek watershed, Marin County (Garza personal communication), six miles to the south.

Coho Salmon (Oncorhynchus kisutch) in Pine Gulch Creek, Marin County, CA. 2002 Monitoring Report

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