2021 Spawner Surveys Continue in Marin County Creeks with Mixed Results

A staff member snorkeling a woody debris pile in Redwood Creek. NPS/ Dustin Geisen

February 16, 2021 - The San Francisco Bay Area Network fisheries crew is continuing their weekly surveys up Marin County creeks in search of spawners and redds. The first week of February was one of their most productive of the season to date. It followed a storm that significantly increased flows, enabling coho salmon and steelhead trout to migrate to their preferred spawning habitat upstream. On Olema Creek, the crew counted six live adult coho, five coho carcasses, seven live adult steelhead, and one steelhead carcass. They also recorded several new redds for both species. This season's redd counts on Olema might now be higher than for the previous generation! However, finding coho and steelhead in the creek at the same time complicates preliminary redd estimates for each species. Biologists need to do more data analysis to arrive at more accurate estimates.

Unfortunately, the fisheries crew hasn't found any new spawners or redds in Redwood Creek. They had counted two redds and a live coho spawner in January.

In addition to spawner surveys, the crew conducted a winter habitat survey in the Muir Woods section of Redwood Creek. On day one of the survey, they evaluated in-stream habitat composition. This involved classifying individual units of creek sections to habitat type (pool, flatwater, riffle, etc.). They also measured unit dimensions including length and maximum depth. Then, for day two, the crew donned their wetsuits and snorkel gear to count year-old coho and steelhead in randomly selected pool and flatwater units. They didn't find very many—no surprise given the low summer 2020 snorkel counts. It’s also likely that many young coho have already moved downstream as they begin the process of smoltification.

The fisheries crew will continue conducting spawner surveys and will begin preparing for smolt trapping season in early March.

For more information

• San Francisco Bay Area Network Salmonid Monitoring webpage
• Pacific Coast Science & Learning Center Coho & Steelhead webpage

San Francisco Bay Area Coho and Steelhead Blog

• Contact Fisheries Biologist Michael Reichmuth

See more from the San Francisco Bay Area Coho and Steelhead Blog and Bay Area Nature & Science Blog

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