Heavy rains bring king salmon back to bay area

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Fall rains sent a wave of Chinook Salmon swimming into Bay Area streams, a sudden turn of fortune for an iconic species that has struggled after years of drought.

A living link between our mountains and the coast, the fish responded to the fierce atmospheric river at the end of October by rushing to the regiothe once parched shore of nrs, say biologists, frequenting places they have never been seen.

“It’s remarkable,” said Joe Sullivan, fisheries manager for the East Bay Regional Park District. The storm “prompted them to surrender to the first freshwater slug they could find,” as they returned from their epic ocean migration to spawn.

In recent years, populations of chinook salmon, also known as king salmon, have collapsed with astonishing speed – and even this current race is unlikely to end well if more rain does not come.

But it’s an encouraging sign that the huge fish still yearn to spawn in our waters.

The salmon was presumed to have disappeared for good from Hayward’s San Lorenzo Creek. But dozens were seen swimming in the stream’s urban flood control channel. In the South Bay, others went up Los Gatos Creek to Campbell.

Last year, only one fish was reported in the lower reaches of Alameda Creek. Now there are many of them, trapped in a small pool created by a concrete barrier near the pillars of the BART.

And for the first time in history, National Park Service biologists have documented a female Chinook on a gravel nest in Marin County’s Olema Creek, which runs through Point Reyes Station to Tomales Bay. Nearby, also for the first time, a pair of salmon were spotted swimming in Bolinas’s Pine Gulch Creek.

The recent storm triggered the migration of chinook salmon to the lower Alameda Creek in Fremont, California. A cement dam keeps them from moving upstream, but construction of a fish migration ladder is nearing completion. (Photo courtesy of Dan Sarka, Alameda Creek Alliance)

According to the Turtle Island Restoration Network, a recently restored stretch of San Geronimo Creek received a historic 10-inch rainfall over a 24-hour period – and in three days, chinook salmon were swimming through the rafts and molding themselves into pools. In Sonoma County, fish swam from San Pablo Bay to Sonoma Creek.

The fall run chinook are the largest wild salmon species in the Pacific.

They are powerful and red in color, with black spots on the back. Weighing up to 30 pounds, the fish are born in freshwater and then adapt to saltwater on a massive migration to the Pacific Ocean, where they live for three years. Then they swim to freshwater rivers to spawn and die.

With the winter rains, the chinook moved to spawn in Los Gatos Creek and then died. (Photo courtesy of Mike Tamaro, South Bay Clean Creeks Coalition)

“Tall and handsome,” Sullivan said. “That’s the best way to put it.”

Chinooks seen in Santa Clara and Alameda counties were likely born in hatcheries in the Central Valley, or are offspring of hatchery-born fish, and then introduced to the bay, said Jeff Miller of the Alameda Creek Alliance. In contrast, fish from the coastal Marin, San Mateo and Santa Cruz rivers were born in wild waters.

Each October and November, when the rivers cool, they move up from the ocean to estuaries and the bay, waiting for storms, according to Jerry Smith, fish expert and retired professor of biological sciences. at San Jose State University.

Historically, chinooks were abundant. But artificial migration barriers, such as roadblocks, have reduced their numbers. There has been pollution and poaching. Recent droughts have been exceptionally punitive, making rivers hot and dry.

Chinook has an advantage compared to other salmon, Miller said. Baby fish can swim safely to the ocean in the spring – so don’t perish in the dry rivers of summer.

But the flows in the recent winter were too low or too late to welcome adults again for breeding. In the Guadalupe River watershed in South Bay, home to the country’s southernmost salmon runs, drainage from Anderson Dam last year for a seismic modernization project meant no water was released for fish, according to Steve Holmes, founder and executive director of the South Bay Clean Creeks Coalition.

In the 1990s, at least 2,000 fish were counted in the Guadalupe River watershed in San Jose, Holmes said. In recent years, on average, only 150-200 fish have been observed.

In Fremont’s lower Alameda Creek, the last notable year was 2006, when a handful were spotted. Only one was seen in 2012, then another in 2018. Two were seen in 2019, Miller said.

But this year’s major storm, October 24, changed everything.

For humans, this atmospheric river was perilous. A concentrated plume of moisture hit the bay area with rain and high winds, chopping down trees and chocking cars.

For the fish, however, it was a godsend – perfectly timed for their courtship rituals.

“All the fish were waiting for water and lower temperatures,” Holmes said. “So when this atmospheric storm hit and the flows increased, they started to go up. “

The recent storm triggered the migration of chinook salmon into the lower Alameda Creek at Fremont. They are prevented from going upstream by a cement spillway, but construction of a fish migration ladder is nearing completion. (Photo courtesy of Dan Sarka, Alameda Creek Alliance)

It was brief, he added. In a window of two or three days, some have gone far. But most of the others, lagging behind, are still waiting.

Hopes are now based on a successful storm parade. Each could set off a large pulse of water, the biologists said, giving other fish a safe route to spawning grounds.

“If the flows are right and the fish are in the right place on the river, they’re going to kind of hopscotch,” Holmes said.

But if the storms don’t come, those pools will shrink and today’s abundant chinook will be trapped in the standing water tomorrow.

“We’ve had a good storm, but the majority of the fish are still in the bay, waiting,” said Holmes. “We really need more.”


Help count the fish

South Bay: The South Bay Clean Creeks Coalition begins monitoring fish populations. An introductory organizational meeting will be held on Tuesday, November 30 at 6 p.m. at the Campbell Community Center at 1 W. Campbell Ave. There is also a Facebook Live option: https://www.facebook.com/FriendsLGCreek/photos/a.564801383558771/4795046380534229/

Alameda County: If you see any fish in the Lower Alameda Creek Flood Control Channel that you suspect are salmon or rainbow trout, November through April, please contact Jeff Miller, Alameda Creek Alliance, jeff@alamedaacreek.org.

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