Lagunitas Creek updates from Marin Water's fisheries team

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February 20, 2025 - A Season of Extremes

Marin Water’s fisheries crew was back in the water on Feb. 11, following a massive flood the previous week. We observed 35 adult coho salmon, a significant number for February, seemingly undeterred by the flood and the time of year. While the coho salmon run in Lagunitas Creek is not quite finished, and the steelhead run is still in full swing, it’s safe to say that this spawner season has been extraordinary. 

The most impressive statistics for the 2024-2025 spawning season include: 

• The largest Chinook salmon run on record (242 adults) 
• The second-largest coho salmon run on record (1,186 adults) 
• The most coho salmon redds (nests) observed in a single day (117) 
• The most significant flood in 19 years (peaking at 6,210 cubic feet per second at the Samuel P. Taylor gauge) 

A common misconception is that salmon are more abundant in wet years, which is understandable since many people don’t see salmon unless local streams have enough water, at the right time, for big fish to migrate into their neighborhoods. Coho salmon have been highly visible this year, thanks to frequent rain and swollen streams, but their abundance owes much to rain that fell three years ago. 

In 2021, the Lagunitas Creek watershed received an astonishing 37 inches of rain between October and December, allowing Coho Salmon to migrate far into headwater streams to spawn. The following three months were exceptionally dry, and low stream flows allowed all those eggs to incubate in peace. Just as we began to worry about baby salmon trapped in drying redds, April rains re-wetted those streams. Those exceptional incubation conditions led to a record number of smolts (downstream migrants) entering the ocean in 2023. Despite below-average survival in the ocean (see November’s Fish Forecast for possible reasons), this cohort came very close to breaking a 30-year abundance record. Did the big flood impact this year’s salmon eggs?

Did the big flood impact this year's salmon eggs? 

High stream flows can wash away salmon eggs, smother them in fine sediment, or bury them so deep in gravel that the fry can’t escape. Fortunately, most coho salmon this year spawned in tributary streams, where flows were not as destructive as they were farther downstream. We have never seen this particular combination of so much spawning in tributary streams followed by such a large flood, so it’s anyone’s guess how many juvenile coho will emerge from the streambed over the next couple of months. Early March is typically when we see the first tiny fry swimming in shallow, slow-moving stream margins. It will come as a great relief to see those little fish once again.