Nov. 18, 2024

Creek Notes: The Lagunitas Creek Fish Forecast for 2024

Greetings! Eric Ettlinger from Marin Water's fisheries team here with an encouraging update for this salmon season. 

Salmon have returned to Lagunitas Creek! On November 5, Marin Water biologists observed two Chinook (aka “king”) salmon swimming in the “swimming hole” in Samuel P. Taylor State Park and then saw the first redd (gravel nest) two days later. Chinook are the first of our salmonid species to return from the ocean, aside from the extremely rare pink salmon that arrive earlier. We often see the first coho salmon, and the occasional chum salmon, in mid-November. Steelhead trout are always the last species to arrive, generally appearing around the New Year. Lagunitas Creek is unusual among California streams for having recent records of four of the five species of Pacific salmon. 

While the first salmon observations of the season are always exciting, we are already waiting in anticipation of the upcoming coho salmon run, which could be one of the largest in decades. How does Marin Water predict the number of returning salmon and how accurate are those predictions? We base our predictions on five metrics, and the accuracy of our predictions depends on whether those metrics show agreement or not. 

The first metric is the size of the coho salmon run three years ago. Coho have a three-year life cycle, and the 2021-22 run consisted of nearly 700 fish, which was well above average. The second metric is the number of smolts (downstream migrating fish) that left Lagunitas Creek. In 2023, a record 50,000 coho salmon smolts emigrated from Lagunitas Creek, which was nearly 400% of average. These two metrics suggest that massive numbers of coho salmon are approaching, but a third metric has tempered our hopes for an all-time record. Each year, a small proportion of Coho Salmon, called “jacks,” return a year early and provide a glimpse of how the rest of their cohort is doing out in the ocean. Last year we saw an above-average number of jacks, but well below the record. 

Two additional metrics added a bit more cold water to our hopes for a record-breaking run. Smolts in 2023 were smaller than average, and therefore easier for seabirds to eat. Upwelling, a process that transports nutrients from the deep ocean to the surface and feeds plankton, was also only average in 2023. 

When seen together in the table below, one can see that predicting salmon runs is not always easy. However, most indicators suggest that a large Coho Salmon run is approaching and getting excited about that possibility is very easy indeed.

-Eric Ettlinger
Marin Water Aquatic Ecologist