The salmon spawning season is always a long-awaited period of wildlife spotting within the Lagunitas Creek Watershed. As the California Coastal coho salmon are critically endangered, efforts to monitor this keystone species are performed during the juvenile stages of their life cycle within the freshwater creeks, until they return as adults to start the cycle again. Data for each of the three cohorts allows stronger analysis towards how the population is persisting, thriving, and progressing towards no longer being endangered.

This year, winter rains brought in coho salmon throughout December with peaks occurring around the second and last weeks of the month. Salmon were spotted all throughout Lagunitas creek, with record accounts in Olema creek, as many residents and visitors witnessed the action at Leo T. Cronin Fish viewing area and at the Inkwells. However, as the fish were able to migrate further upstream, the tributaries of San Geronimo creek soon became a hot spot for spawning.

The Salmon Protection And Watershed Network (SPAWN) is in charge of monitoring the smaller tributaries of San Geronimo creek, the upper portion and headwaters of the Lagunitas Creek Watershed. Although access is dependent on the timing of rain events and flow, coho were seen populating creeks that don’t often get much action. Arroyo and Woodacre creek are the stronghold tributaries, but this year we saw more spawning in Larsen Creek and Montezuma creeks as well.

Ayano Hayes, Watershed Biologist with SPAWN, shares “In my four years of monitoring the upper tributaries, I’ve never seen so many live fish in one survey day! On Arroyo creek we witnessed 19 coho salmon actively spawning and 28 coho salmon in Woodacre creek.” Another observation Ayano made while surveying, “This year, salmon built their nests in habitat that have not been utilized for years. Riffles zones that I have always thought would be great spawning sites were finally used. It’s great to see the upper tributaries providing suitable habitat for optimal nest digging while decreasing the competition elsewhere in the system.”

As the coho season comes to an end, the rough count for total nests (redds) within the upper tributaries provides a strong standing for this year’s cohort. In Arroyo creek, there have been a total of 20 redds recorded so far while in Woodacre creek, 18 redds. SPAWN has also recorded the most amount of redds seen in Montezuma creek since the first redd was documented in 2002-03. There have been 4 redds documented within the lower 0.1 mile section of Montezuma, before the creek flows through private property, ending the survey. Similarly in Larsen creek, overcoming culverts, more redds have been seen further upstream with a total of 4 redds throughout the 0.25 mile reach. Larsen creek has not seen much spawning over the last decade, with the last documented year of over 4 redds being in 2004-05 with 7 redds.

Ayano notes, “With more rain predicted, and the stealhead season upon us, more surveying will be done throughout the next month. However, at this point in time we are just under the collective coho redd total documented for the strongest cohort back in 2021-22 for the San Geronimo Tributaries- 46 redds to 51 redds.” As the coho cohort that wavers between the strongest and the weakest class, this is incredible news for this cohort’s recovery.