Marin storms complicate outlook on endangered salmon spawning

The intense rain storms this year acted as a double-edged sword for Marin County’s endangered salmon runs and the biologists who monitor them.

While providing ample water in local creeks and streams for adult coho salmon, chinook salmon and steelhead trout to reach their spawning grounds, the heavy storms also worked to conceal the level of success they had in breeding and laying their eggs nests, known as redds.

Marin Municipal Water District ecologist Eric Ettlinger said the persistent storms and turbid waters kept salmon surveyors from being able to conduct their normal monitoring for several weeks. So far, counts of salmon egg nests remain below average or low, depending on the species.

“Unfortunately, we know of some redds that definitely were destroyed and we suspect that others were destroyed and the eggs washed away,” said Ettlinger, who monitors the Lagunitas Creek watershed.

“We also know that some of the redds survived because we are counting the smolts, the juvenile fish that are heading to the ocean,” Ettlinger said. “We’re seeing coho fry, which are this year’s salmon babies, in our smolt trap. We know there was successful reproduction. At this point, we just don’t know how much.”

Marin County has the largest population of wild endangered coho salmon from Monterey Bay to the Mendocino-Sonoma county line. Once believed to have numbered in the thousands, coho populations dwindled to the hundreds during the 20th century because the construction of dams blocked miles of former spawning grounds and tributaries.

Coho salmon generally have three-year life cycles. After hatching, the fry rear in freshwater for about 18 months before heading to the ocean as smolts. After another year and a half, they return as adults to the same creeks and streams they were born in to spawn and then die.

Ettlinger and his team counted 99 coho egg nests in the Lagunitas Creek watershed. The number is higher than the 63 found last year, but still below average.

Similar results were found in other coho salmon strongholds in Marin. In San Geronimo Creek and other tributaries to Lagunitas Creek, surveyors with the nonprofit Salmon Protection and Watershed Network, or SPAWN, found 15 coho redds.

“With so much rain, it would give a lot of the fish access to these upper tributaries easier than ever before,” said SPAWN watershed biologist Ayano Hayes. “Yet it was already kind of a small population to begin with. We didn’t see too much spawning.”

No coho salmon redds were found in Redwood Creek or Pine Gulch Creek, said National Park Service fisheries biologist Michael Reichmuth.

“It didn’t look good in terms of coho at least,” Reichmuth said. “We didn’t see much spawning, period. That said, we also didn’t get into the creek a whole lot during the January onslaught of rain.”

However, coho fry have been found in Olema Creek, which is a tributary of Lagunitas Creek.

“I think it’s really going to be our juvenile surveys that we do in the summer that will give us a better picture of what happened in the wintertime, or at least what survived in the wintertime,” Reichmuth said.

The amount of rain will help to prevent creeks from drying out as the young salmon fry rear in freshwater this summer, barring any major heat waves, Reichmuth said.

While this year’s coho spawning appears to be lackluster for now, surveyors said they have been seeing record numbers of coho smolts heading out to the ocean this spring. Reichmuth said more than 1,100 coho smolts were counted in a single day on Olema Creek.

“Since the park started smolt trapping in Olema Creek, this is by far the biggest year I’ve seen,” Reichmuth said, noting that the park service has monitored smolts since 2004.

Many of the ocean-bound coho are large and healthy, giving them a better shot at survival and better chances of a larger spawning run in the winter of 2024-2025, Reichmuth said.

Similar results have been seen in Lagunitas Creek.

“Right now we’re seeing record numbers of coho smolts going to the ocean,” Ettlinger said. “If they survive reasonably well, we could be looking at record numbers of adults coming back in a year and a half.”

SPAWN has counted nearly 1,000 coho salmon smolts since mid-April, which is encouraging, though lower than some previous years, Hayes said.

While coho counts were low, Lagunitas Creek had the largest number of chinook salmon spawners since the district began counting in 2001, Ettlinger said. About 153 adult chinook salmon were counted in the stream since November.

Arriving earlier than coho, however, many of the chinook salmon eggs were likely washed away by the powerful storms in late December and early January, Ettlinger said.

Reichmuth said a chinook salmon redd was found in Redwood Creek for the second year in a row.

For the upcoming winter, Lagunitas Creek is expected to have an average run of coho depending on what ocean conditions are like, Ettlinger said. In the meantime, surveyors are hoping to see more young salmon in the stream this summer.

“Waiting with bated breath,” Ettlinger said. “I’m really looking forward to seeing how many of the young coho survived the stormy winter. We’ll start looking for them next month.”