As California drought clouds future, Chinook salmon return to Sonoma Creek to spawn

Chinook salmon are back, baby!

After a rush of cold-running water brought by the atmospheric river in late October, Sonoma Creek, along with other streams across the Bay Area, saw a surge in flow giving Chinook, or king salmon, the perfect conditions to make their way upstream from the Pacific.

The adult fish are now making their way from San Pablo Bay, swimming up Sonoma Creek to prepare their nests and spawn a new generation of offspring in the water that gushes down from Sugarloaf Ridge State Park high above Sonoma Valley.

They are travelers on a long and tenuous journey to spawn and die in the rivers and creeks where they were born ― all so their young can return back to the ocean and begin the cycle again.

A threatened species, the Chinook are fighting to hang on in Northern California and across the Pacific Northwest amid intense weather swings and worsening climate conditions, including severe drought.

For those adults who reach the headwaters of the Sonoma Creek watershed, they could be leaving their young to survive in shrinking pools as conditions dry out later next year, according to Ryan Watanabe, district fisheries biologist for the California Department of Fish and Wildlife.

“From a Chinook salmon perspective, maybe getting up there wasn’t necessarily the best,” Watanabe said. “It might have been better if they stayed lower in the system where there’s plenty of gravel and habitat and it’s just a little wider and deeper.”

On the other hand, if they stayed in lower tributaries, people hiking through Sugarloaf wouldn’t get the chance to see them or learn about the prized ocean-going fish and their fragile stake in the local watershed, Watanabe said.

The creek ecosystem also benefits from the nutrients that wouldn’t otherwise be there when the adult fish die after spawning.

“Right now we’re optimistic and happy,” said Steven Lee, senior scientist and research program manager at the nonprofit Sonoma Ecology Center, which monitors the salmon run and helps operate Sugarloaf Ridge State Park. “Now we need to get that rainfall to create stream flow throughout dry season.”

The past year of drought conditions have severely impacted the local runs of salmon, including Chinook, as well as the even more endangered coho, Lee said.

Steelhead trout, which also are born in freshwater streams and can return from the ocean and spawn several times over their lives, have been in the same precarious spot amid the drought, Lee said.

Scientists have never confirmed in Sonoma Creek the presence of coho, which among the three species need the most pristine habitat to thrive, especially the cold, clear water found in forested streams. Steelhead, because of their more pliant lifecycle, can better withstand some low-water years, Lee said.

The return of the Chinook salmon, the heftiest of the three fish, weighing in locally at up to 30 pounds, signifies, at least momentarily, that flow conditions are suitable in Sonoma Creek.

No organization is conducting a spawning survey to tally the number of Chinook in the watershed as of now, said Watanabe, though they estimate the late-October storms have brought many of them up the creek.

“Chinook salmon have been recorded in Sonoma Creek in Adobe Canyon in the past, sometimes seen about one-half mile below the boundary of the park,“ said Cyndy Shafer, natural resource program manager for California State Parks’ Bay Area district. ”It’s exciting to have them further up, in the park“

On the Russian River, where Chinook, coho and steelhead migrate upstream to spawn, biologists maintain an annual count recorded at the fish ladder near Forestville.

According to a January tally, officials spotted 602 Chinook, 246 coho and 174 steelhead.

Just days before the recent atmospheric river, Sonoma Water conducted two salmon spawning surveys on Oct. 7 and Oct. 14, according to the agency’s website. These surveys were conducted in Dry Creek and the upper Russian River. No salmonids or redds were observed, officials said.

Results of a count conducted since the recent rains were not available.

In smaller streams like Sonoma Creek, the fish populations depend on stretches of riffled water where they spawn and on deeper pools with where their young grow before they are ready to head to the ocean.

But the drier outlook this year amid a La Niña weather pattern has officials from the Sonoma Ecology Center like Lee and others anxious about the prospects for more rain. If more storms don’t arrive this year and next, those pools are bound to shrivel, stranding young salmon in stagnating water.

Another dry winter and spring like the last two could prevent the young salmon from surviving and making their odyssey back to the sea.

For the moment, flows in Sonoma Creek are suitable, at more 23 cubic feet per second at the Kenwood gauge, where the creek is over 4 feet deep. By contrast, at the peak of last month’s historic atmospheric river, the creek was flowing at over 2,000 cfs — about a 7000% increase from the 13-year average of .29 cubic feet per second for late October.

The adult fish, which typically gather in wait at the mouth of their natal streams, were triggered by the high flows to begin their upstream trek.

“Its almost like they got tricked into thinking these tributaries are better suited for them than they actually are,” Watanabe said.

If the rainfall continues as it has over the past four weeks, experts hope that the Chinook population could do better this year, Lee said.

'All part of nature’

Chinook salmon can return to the streams of their birth after one to five years at sea. The Sonoma Creek run had a successful spawning season a few years ago, so it’s possible that these are their offspring returning to spawn, according to a Sonoma Ecology Center Facebook post.

The females are usually the first ones to reach an area in the creekbed where they will lay their eggs, Lee said. When they arrive, they find a spot to build a nest and use their tails to excavate a stream bed and get rid of the finer sediments, leaving a spot with courser cobbles for the eggs to rest.

When the males arrive, the mating rituals begin. There’s usually competition where males are jockeying for the females. Once the females lay their eggs, the males will fertilize them and the females will begin guarding them.

Spawning season is a vulnerable time for salmon, and the public needs to be careful by keeping out of the creek and off the streambanks so as to not to disrupt them, said Shafer, the State Parks program manager.

“We need to be more careful,” Lee said. “If everybody runs up to the creek...it will be a problem” he said.

If the adults that are moving upstream now into the steep headwaters of Sonoma Creek successfully spawn, their young will have to endure all of the dry season — spring, summer and fall, potentially — before the arrival of storms late next year when they will move out to the ocean, Lee said.

If the pools do get too small for the reared Chinook, nature will do it’s thing, Watanabe said.

“It’s a balance,” he said.

“The ecosystem will take care of it. Nothing will be wasted,” Watanabe said. Other wildlife will eat them and their nutrients will return to the water.

“It’s all part of nature.”

You can reach Staff Writer Alana Minkler at 707-526-8511 or alana.minkler@pressdemocrat.com. On Twitter @alana_minkler.