2020 Coho Salmon Spawning Season Off to a Dry Start

An adult female coho spawner in Redwood Creek from a prior season. As of late-November, the salmonid monitoring team has not spotted any coho spawners. NPS / Jessica Weinberg McClosky

November 2020 - After a dry year marked by wildfire, the coho salmon spawning season is off to a similarly dry beginning. As of the end of November, the salmonid monitoring team had not spotted any coho salmon in Redwood and Olema Creeks. During dry summer months, once fast-flowing streams can turn into slow-flowing pools, and at Muir Beach, sandbars block Redwood Creek from flowing into the ocean. Before salmon can start swimming upstream to spawn, enough rain must fall to increase water flow and reconnect the streams to the ocean. Fortunately, it is still early in the spawning season.

The monitoring team typically sees peak coho spawning around December, even in years with plentiful rainfall in October and November. The team has started preliminary spawner surveying in Redwood and Olema creeks. Once streamflow is high enough, they'll begin weekly monitoring. Monitoring involves counting live adults, adult carcasses, and redds, which are gravel nests that female salmon create to shelter their eggs.

The coho salmon returning to spawn this year are descendants of the winter 2017-2018 cohort. In January 2018, biologists released 188 hatchery raised adult coho salmon to supplement the population in Redwood Creek. The 2020-2021 spawner season is the first time the offspring of these hatchery raised adults are returning to their natal stream, and the salmonid team is hoping for robust returns. Based on the number of smolts that emigrated out of the creeks in 2019, that would mean counting around 25 adult coho in Olema Creek and 60 in Redwood Creek this spawner season.

For more information

• Read the Summer 2020 Juvenile Coho & Steelhead Monitoring Summary
• San Francisco Bay Area Network Salmonid Monitoring webpage
• Pacific Coast Science & Learning Center Coho & Steelhead webpage
• Contact Fisheries Biologist Michael Reichmuth

By Science Communication Intern Laurel Teague, San Francisco Bay Area Inventory & Monitoring Network

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