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Claudia Mayo, left, and Jay Held with the Russian River Salmon and Steelhead Monitoring group, dip coho smolt from a fish trap as they prepare to count, measure, weigh and tag the fish, Wednesday, April 13, 2022 near the confluence of Felta and Mill Creeks. Mayo is an intern and environmental sciences intern from Sonoma State University and Held is a lab assistant/fisheries biologist with the monitoring group. (Kent Porter / The Press Democrat) 2022

Endangered coho salmon battered by 3rd year of drought. Here’s why it matters

They were once abundant in the cold, clear water of North Bay creeks and streams. Now, the survival of coho salmon is being challenged like never before.

The coho has a three-year life cycle that takes it from stream to ocean and back to stream to spawn the next generation.

But the changing climate now threatens the species at every life stage, raising new questions about their recovery.

A coho smolts to be measured weighed and tagged, Wednesday, April 13, 2022 in Mill Creek near Healdsburg as part of the Russian River Salmon and Steelhead Monitoring program. (Kent Porter / The Press Democrat) 2022
A coho smolts to be measured weighed and tagged, Wednesday, April 13, 2022 in Mill Creek near Healdsburg as part of the Russian River Salmon and Steelhead Monitoring program. (Kent Porter / The Press Democrat) 2022

It’s not just a species at stake. At risk is the very resilience of the forest and watershed that evolved around them, fed by marine nutrients brought upstream and deposited inland by adult spawners that, after reproducing, die and decompose.

“Salmon are a keystone species, which means they perform a really important ecosystem service,” said Sarah Nossaman Pierce, a California Sea Grant fisheries biologist with the Russian River Monitoring Program. “Salmon and steelhead (trout) bring marine-based nutrients into the system and essentially feed the forest, plants, birds and wildlife.”

The challenge, she said, is “ecosystem resilience”

“People say, ‘Why do you care about the salmon?’ Unfortunately, if they can’t survive, human beings aren’t far behind,” she said.

Rains bring false hope

Recent rains in the Russian River watershed swelled streams as the peak migration of yearling coho salmon, called smolts, was getting under way in early May. But stream levels are beginning to decline again to levels of a few weeks earlier, when the young fish faced the lowest stream flows ever seen so early in the year.

Some creeks ran dry, requiring an annual smolt rescue and relocation program — fish and wildlife personnel pull stranded fish from isolated puddles and pools and transport them to survivable streams — to begin earlier than ever.

“It’s not happy news,” said Mariska Obedzinski, an expert with California Sea Grant and coordinator of the Russian River Salmon and Steelhead Monitoring Program.

Zac Reinstein, with the Russian River Salmon and Steelhead Monitoring group, transports coho salmon in an aerated water canister to another location, helping the smolts through low water flows in Mill Creek, Wednesday, April 13, 2022 near Healdsburg.  Reinstein is a fisheries biologist.  (Kent Porter / The Press Democrat) 2022
Zac Reinstein, with the Russian River Salmon and Steelhead Monitoring group, transports coho salmon in an aerated water canister to another location, helping the smolts through low water flows in Mill Creek, Wednesday, April 13, 2022 near Healdsburg. Reinstein is a fisheries biologist. (Kent Porter / The Press Democrat) 2022

The Russian River’s once celebrated salmon populations have long been imperiled by logging, development, gravel mining and other human activities that have eliminated flood plains, channelized river and stream flows, and limited the woody debris and shade that keeps the water cool enough for young fish to survive.

More intense and frequent droughts have further eroded conditions, not just for the coho, but for steelhead and chinook salmon, both listed as threatened under the federal Endangered Species Act.

Dry years once were viewed as a threat primarily to tiny fry summering in small, coastal streams.

But recently, streams have been low for so much of the year that adult fish sometimes struggle to swim upstream to spawn in the winter. The gravel nests, or redds, where they deposit their eggs may become stranded and dried out before the eggs hatch.

“We almost lost our native fish.” Sarah Nossaman Pierce

Summer heat has left young fish trapped in shrinking pools of warm and oxygen-poor water until they die from heat or suffocation as those pools evaporate. Those that survive may be challenged to find sufficient flows to get downstream when spring comes.

The threat to multiple life stages at once for an already vulnerable species is alarming, especially over successive years.

A helping hand

The region’s coho were on the brink of extinction 20 years ago when a few hundred wild juveniles were collected from West Sonoma County’s Green Valley Creek and other small streams. That effort led to the Coho Recovery Broodstock Program at Lake Sonoma, which hopes to rebuild a self-sustaining population.

A coho salmon smolt is measured, Wednesday, April 13, 2022 in Mill Creek near Healdsburg as part of the Russian River Salmon and Steelhead Monitoring. (Kent Porter / The Press Democrat) 2022
A coho salmon smolt is measured, Wednesday, April 13, 2022 in Mill Creek near Healdsburg as part of the Russian River Salmon and Steelhead Monitoring. (Kent Porter / The Press Democrat) 2022

The Russian River Monitoring Program, meanwhile, was established to gauge the recovery program’s effectiveness and identify bottlenecks to reproduction. Teams from California Sea Grant, Sonoma Water and other partners trap and measure smolts, count young fish, survey salmon in later stages of development and assess stream conditions. Individual fish also are tracked through transponders implanted inside them.

Nossaman Pierce took part in collecting young fish for the initial broodstock and remains cautiously optimistic.

“We almost lost our native fish,” she said recently at the edge of Green Valley Creek, while a crew tended to a smolt trap there. “Literally, this population would have been gone a few years after we started this program.”

Late last summer, members of the monitoring program mapped 36 streams in the lower Russian River watershed. They found that pools that had hosted about half of all coho and steelhead juveniles in earlier surveys remained wet. Another 40% were completely dry; about 10% were intermittent.

It’s not known how many fish perished, Nossaman Pierce said.

A coho salmon smolt is scanned to see whether the fish is tagged or wild, Wednesday, April 13, 2022 in Mill Creek near Healdsburg, as part of the Russian River Salmon and Steelhead Monitoring. (Kent Porter / The Press Democrat) 2022
A coho salmon smolt is scanned to see whether the fish is tagged or wild, Wednesday, April 13, 2022 in Mill Creek near Healdsburg, as part of the Russian River Salmon and Steelhead Monitoring. (Kent Porter / The Press Democrat) 2022

Come winter, abundant early season rain gave adult salmon and steelhead access to small tributaries they hadn’t had been able to reach for years, prompting cheers in the wildlife community.

But the ensuing months were so dry that streams quickly receded, leaving many of the gravel nests they had created at the edge of shallow riffles high and dry, along with the eggs.

“It was a close call. I mean, if this rain didn’t happen, it could have been pretty much a complete loss, or near a complete loss, of a class of coho smolts.” Gregg Horton

Observations this spring were discouraging: 28% of the redds were dry or partially dry, Nossaman Pierce said.

Several hundred smolts and other young fish, meanwhile, were stranded in a tributary to Green Valley Creek, said Coho Salmon Recovery Coordinator David Hines, a senior environmental scientists with California Department of Fish and Wildlife.

Usually the problem is summer disconnection where a creek should meet up with the river but runs dry, Hines said. Any rescue, in which an electric shock is applied to the water and the fish quickly netted, is required in late May or early June, he said.

With each individual fish having only three years of life to rear in freshwater, swim to the ocean and mature enough to return upstream to spawn, a few years of drought could prove catastrophic for the coho population — most of which is hatchery born.

“That’s what we’re living with,” Nossaman Pierce said. “One poor year is impacting three year classes of fish. And if they keep taking these hits every year, you’re not going to be able to step away, even with the broodstock program. The conditions just can’t support this.”

Losing ground

Since the first release of hatchery offspring into the watershed, the number of adults returning to spawn has risen from a mere handful in 2004 to an estimated 763 in the 2017-18 season, according to the Russian River monitoring program.

By 2020-21, that number dropped back down to 214, with adults observed in only eight of 33 surveyed coho-bearing streams, the program reported. A similar, though less extreme, reduction in steelhead adults was observed as well.

From left, Jay Held, Claudia Mayo and Zac Reinstein, with the Russian River Salmon and Steelhead Monitoring group, tag, weigh, measure and collect DNA samples from coho smolts Wednesday, April 13, 2022 near the confluence of Felta and Mill Creeks. Held is a lab assistant/fisheries biologist, Mayo is an intern and environmental sciences intern from Sonoma State University and Reinstein is a fisheries biologist. (Kent Porter / The Press Democrat) 2022
From left, Jay Held, Claudia Mayo and Zac Reinstein, with the Russian River Salmon and Steelhead Monitoring group, tag, weigh, measure and collect DNA samples from coho smolts Wednesday, April 13, 2022 near the confluence of Felta and Mill Creeks. Held is a lab assistant/fisheries biologist, Mayo is an intern and environmental sciences intern from Sonoma State University and Reinstein is a fisheries biologist. (Kent Porter / The Press Democrat) 2022

Federal fisheries managers have established a target of 10,100 adult coho salmon returning each winter to the Russian River basin as the recovery baseline, so that leaves a long way to go.

And they appear to face another harsh summer ahead, though mid-April rainfall offered an unexpected buffer just as conditions appeared to offer little hope.

“It was a close call,” said Gregg Horton, principal environmental specialist with Sonoma Water. “I mean, if this rain didn’t happen, it could have been pretty much a complete loss, or near a complete loss, of a class of coho smolts.”

Instead, strong flows filled streams and reconnected tributaries with the main stem Russian River just in time for the peak coho smolt migration in early May, Horton said.

It may be enough to see the yearling fish through their out-migration, though stragglers in late June could struggle, he said.

It’s a different story for the young hatchlings that need to spend the summer feeding and rearing in streams with little moisture banked in the surrounding landscape to replenish them after three extremely dry months at the start of the year.

Zac Reinstein, from left, Jay Held and Claudia Mayo, left, with the Russian River Salmon and Steelhead Monitoring group, fix holes in a fish trap with river sand in Green Valley Creek, Wednesday, April 13, 2022.  Reinstein is a fisheries biologist, Held is a lab assistant/fisheries biologist and Mayo is an intern and environmental sciences intern from Sonoma State University with the monitoring group. (Kent Porter / The Press Democrat) 2022
Zac Reinstein, from left, Jay Held and Claudia Mayo, left, with the Russian River Salmon and Steelhead Monitoring group, fix holes in a fish trap with river sand in Green Valley Creek, Wednesday, April 13, 2022. Reinstein is a fisheries biologist, Held is a lab assistant/fisheries biologist and Mayo is an intern and environmental sciences intern from Sonoma State University with the monitoring group. (Kent Porter / The Press Democrat) 2022

That means over-summering “young of the year” — fish that emerged from gravel nests in March or so — will likely face the same dire conditions they did last year and during droughts past.

Field crews will be on hand to rescue those they can. But, said Horton, “it’s not an ideal management strategy.”

“These watersheds have been altered by years of development and various land uses, and they’ve lost some of their hydrologic resilience,” he said. “So the habitat is more fragile, essentially, and we have a lot of work still to do with the ecosystem to build resilience for a changing climate. Fish rescue is just a short-term effort to try to save the genetic material that we have out on the landscape right now.”

You can reach Staff Writer Mary Callahan at 707-521-5249 or mary.callahan@pressdemocrat.com. On Twitter @MaryCallahanB.

Mary Callahan

Environment and Climate Change, The Press Democrat

I am in awe of the breathtaking nature here in Sonoma County and am so grateful to live in this spectacular region we call home. I am amazed, too, by the expertise in our community and by the commitment to protecting the land, its waterways, its wildlife and its residents. My goal is to improve understanding of the issues, to find hope and to help all of us navigate the future of our environment. 

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