How Much Water Do Coho Salmon Need? Researchers Find Surprising Answer
July 9, 2018
Water Deeply by Alastair Bland
For California’s endangered Coho salmon, just a trickle of water may mean survival in the small rivers and streams where the fish spend their first year, researchers found.
In California’s small coastal streams, where hundreds of thousands of Coho salmon once returned each year to spawn, most wild populations now barely cling to survival. Habitat loss and intensive water use have pushed them to the brink; now climate change and increasing competition for water resources could send them over the edge.
However, recent research offers some encouraging findings – that juveniles of Coho salmon, an endangered species in California, can survive in creeks where just a trickle of water remains flowing. Since Coho spend their entire first year in fresh water before heading for the sea, it’s critical that their creeks don’t dry out in the summer.
Scientist Mariska Obedzinski and three collaborators – Sarah Nossaman Pierce, a California Sea Grant Extension specialist; Gregg Horton, a principal environmental specialist at the Sonoma County Water Agency; and Matthew Deitch, an assistant professor of watershed management at the University of Florida – found that less than 1 gallon per second of flow in small streams is all it takes in some creeks to keep pools interconnected.
“We were amazed that fish were able to make it through the summer with just a trickle of water running through [the streams],” Obedzinski, who is also a specialist with the California Sea Grant Extension, said in an interview.
This means that relatively small concessions by water users can have profound implications for struggling Coho runs, and Obedzinski said she hopes her published findings will help motivate water conservation among farmers and rural residents in coastal watersheds.
“Our hope is that people might be more inclined to sacrifice a little water now that they realize it’s not all that much and that it would be really meaningful for the fish,” she said.
A Little Matters a Lot
Obedzinski, whose paper was published in the journal Transactions of the American Fisheries Society, studied four tributaries of the Russian River between 2011 and 2013. She and her colleagues fitted juvenile Coho born in a United States Army Corps of Engineers fish hatchery with transponder tags and released them into their study creeks each spring. Months later the researchers walked the creeks with detection equipment, tracking down the tags and determining whether the fish that wore them were dead or alive.
They observed that fish survival rates were consistently lower in pools that had become isolated by dropping water levels, which caused water temperatures to increase and oxygen levels to fall – and the longer a pool had been disconnected, the fewer salmon had survived. They also observed that minute volumes of moving water would keep salmon alive for months.
“The results of this study have important implications for streamflow management and salmonid recovery efforts,” the scientists wrote. “Our observation that juvenile Coho salmon were able to survive at flows below [3 liters per second], so long as pools remained hydrologically connected, suggests that streamflow improvement projects contributing even a few liters per second could allow rearing juveniles to survive the summer bottleneck in intermittent streams.”
Coho salmon have fared much more poorly in the 20th and 21st centuries than their larger cousins, the Chinook salmon, which remain abundant enough to be fished rather intensively throughout their West Coast range. That’s mostly because Chinook salmon tend to spawn in large river systems that are much more resilient to drought and water diversions than the small creeks favored by Coho, which often go nearly dry in the summer – a natural characteristic which has been exacerbated by human consumption of water.
Also, whereas juvenile Chinook spend only a few months in fresh water – mostly during winter when rainfall is plentiful – before migrating to the ocean, Coho juveniles spend an entire year in the streams where they were born before heading for the sea.
“The fact that they summer in these little creeks makes them really vulnerable, since so many creeks now dry up each summer,” said John Green, a lead scientist with the Gold Ridge Resource Conservation District, in Sebastopol, Calif. His organization, as well as the California Sea Grant
Extension and several conservation groups, is part of a collective called the Russian River Coho Water Resources Partnership. The collaboration is arranged so that research from scientists like Obedzinski can be used to help refine onsite conservation actions. The Gold Ridge RCD, for example, is building rainwater catchment and storage systems for homeowners using scientific data to help set streamflow targets.
Green also said he and his colleagues had persuaded several landowners in the Green Valley and Dutch Bill Creek valleys to release stored water into tributaries when summer flows grow critically low.
“One of our objectives is to get to where we have fewer of those years where the streams dry out in the summer,” Green explained.
The conservation district has built rainwater catchment and storage systems in more than two dozen locations – mostly in the drainage of Salmon Creek, which enters the ocean about 5 miles south of the Russian River’s mouth. Over time these projects, though individually small, should have detectable benefits.
“We expect to see a pattern of less dried-out streams in midsummer,” Green said.
A Changing Landscape
Half-a-million or more Coho may once have spawned in the Russian River and its tributaries. In the 1990s, Green said, the number of returning adults dwindled “down to the double digits.” Some estimates placed the population at less than 10 fish at its lowest point.
Now the fish are bouncing back, at least a little.
“They’ve been given a new lease on life, and that’s thanks to the conservation hatcheries [that rear juvenile fish in tanks and release them into the wild] and the work people have been doing to keep these rivers flowing,” Green said.
Habitat loss, largely from development and logging, has been the main cause of the Coho’s decline, and intensive use of water – for both residential use and agriculture – continues to threaten California’s Coho.
Conventional road-building methods harm the fish, too. Ditches and culverts intercept rainwater and channel it directly into streams. This causes gushing floods in the winter that damage fish habitat. Because less water is able to percolate into the soil and seep later into creeks, it means watersheds dry out more rapidly and more completely in the summer.
“We need to address road networks in these drainage systems because they intercept so much of the water, and we’re working with private landowners now to modify their ditches and culverts,” Green said.
Farther north, in Mendocino, Humboldt and Del Norte counties, Coho salmon have been similarly impacted. Scott Bauer, an environmental scientist with the California Department of Fish and Wildlife, has closely monitored Humboldt County’s cannabis industry and its toll on the environment. For many years, it was standard practice for illegal growers to draw water directly from creeks for summer irrigation, causing the streams to dry out.
County regulations now forbid the direct withdrawal of water from creeks, said Bauer, who believes stream conditions may be improving for Coho.
“It’s amazing what’s happened in the last couple of years,” he said. “People have learned they need to be more careful with water and that they can’t divert directly from streams anymore, and they’re installing storage tanks that they fill up in the winter.”
He said it was already well understood that “every gallon per second matters” for Coho salmon in small creeks. Still, quantifying this information in published data, as Obedzinski and her colleagues have done, “helps to educate the public and bring awareness to the problem,” ultimately generating social changes that benefit the environment, Bauer said.
Bauer would like to see research go a step further and explore not just how much water salmon smolts need to survive, but how much they need to thrive.
“Big fat Coho babies that go to the ocean have a better chance of survival than a skinny fish that barely squeaked by,” he said.
Obedzinski and her coauthors acknowledged that that aspect was not covered in their analysis. “We did not evaluate the size or condition of the fish, nor determine their fate to the smolt and/or adult stages,” they wrote.
While the minuscule amount of flowing water needed to protect young Coho was an encouraging discovery, Obedzinski warned that the results of her work should not be interpreted incorrectly. Coho, she said, may be able to survive a dry summer with just a trickle of water flowing through a stream.
“But that’s the minimum amount of water it takes to keep a population from going locally extinct, not what it takes to have healthy populations,” she stressed. “For the fish to thrive, we need lots more water.”
Salmon season cut short due to drought
June 29, 2018
KCBX By Erika Mahoney/
Time is running out to buy salmon caught in the Monterey Bay. This year's commercial salmon season is short because of the recent drought.
Early Tuesday morning, six people pack a commercial kitchen in downtown Santa Cruz. They work for the Community Supported Fishery (CSF) Ocean 2 Table. This morning, they’re prepping fresh King salmon. They pack coolers with ice and the fish filets, which they deliver to homes and restaurants.
Charlie Lambert is co-founder of Ocean 2 Table.
“We're hoping to have one more delivery out before the season is up, hopefully at the end of this week if not early next week,” Lambert says.
The Monterey Bay’s commercial salmon season ends this Saturday, June 30; a total of just 19 days this year.
Harry Morse is with the California Department of Fish and Wildlife. He says salmon seasons can sometimes last six months. That was the case back in 2014.
“We set the seasons to try and avoid harvest on stocks that are threatened or endangered,” Morse says.
And this year, California’s salmon population is threatened.
“This all coming back to the drought,” says Morse.
Salmon are struggling in the wake of the drought. That’s because salmon reproduce in rivers. And when local rivers were running low, predators could more easily spot and eat young salmon. So the stock that’s just now old enough for harvest is small.
“You know, you can only harvest so many fish when you need to make sure you have enough that come back for reproduction,” Morse says.
This year’s commercial salmon season is the shortest it's been in the past 7 years.
EPA fines NorCal gravel miner for dumping on endangered salmon
June 15, 2018
San Francisco Chronicle By Ted Andersen
The U.S. Environmental Protection Agency hasn't exactly been known for its teeth as of late, but don't tell that to a Humboldt County gravel miner who just got bit by the feds for dumping pollution on endangered salmon.
In court documents filed Monday, Jack Noble agreed to pay a $10,000 fine and undertake extensive remediation efforts to undo an elaborate dumping operation into the protected waters off of the Eel River.
Noble, who owns Van Duzen River Ranch, was originally cited in a 2016 federal complaint for illegally dumping pollution and debris into the Van Duzen River, a major tributary of the Eel River, causing harm to endangered salmon, steelhead and their offspring.
The gravel operations along the river includ dumping "concrete, asphalt, rebar, trees and vegetation, gravel, excavated soil and other construction debris" into the river and on its banks, all without a permit, according to documents on the U.S. Department of Justice website.
Tribe’s salmon protection effort highlighted in new exhibit
June 14, 2018
The Yurok Tribe’s award-winning stewardship of the Klamath River is featured in a new California Academy of Sciences exhibit called “Giants of Land and Sea.”
“Giants of Land and Sea” is set to premiere on Friday at the California Academy of Sciences in San Francisco. On June 12, Yurok Tribal Council Representative Joe James and Yurok Office of Self Governance Director Javier Kinney participated in several opening events at the museum.
“It is an honor to participate in this amazing project. I would like to thank the California Academy of Sciences for sharing our story with the world,” said James, who represents the Tribe’s East District. “As Yurok people, we have an obligation to be strong stewards of the Klamath River, the lifeline of our tribe. This exhibit will help us raise awareness about what is being done to address the struggling salmon runs on our river.”
“Giants of Land and Sea” is a celebration of Northern California’s natural history and is largely comprised of interactive displays centered on “the epicness of the state’s iconic landscape — a place of constant change where people and climate are shaping the future.”
“Since time immemorial, the Yurok people have been the protectors of the Klamath River and that legacy continues to this day,” James said. “When settlers arrived on our shores they were astonished by the natural beauty. They didn’t know that what they were witnessing was shaped by human hands, Yurok hands, and was the result of our cumulative traditional ecological knowledge. Today, we are working very hard to restore the Klamath River and the forests that surround it.”
The Yurok Tribe’s portion of the California Academy of Sciences exhibit, titled “Yurok Voices,” is comprised of a series of three videos, in which Yurok political leaders and fisheries biologists detail the tribe’s enduring effort to revitalize the Klamath’s once substantial salmon runs. The river’s late
summer/early fall run of Chinook salmon, presently the most populous stock, has reached record-low levels in the past three years, according to a press release from the Yurok Tribe. In 2016 and 2017, fewer fish returned to the river than any other time in modern history. Driving the downturn are four fish ladder-less dams, which create poor water quality conditions and block access to hundreds of miles of fish habitat. However, there is a genuine cause for optimism about the future of the Klamath salmon, the press release states.
In 2021, those four dams are slated for removal in what will be the largest watershed restoration project in U.S. history. For nearly two decades, the Yurok Tribe and neighboring tribes have led a campaign to bring the dams down and reopen 250 miles of historic salmon spawning habitat, the press release says. This ecological success story is highlighted in one of the videos included in the exhibit.
“We believe the health of our environment and the health of our river is a direct reflection of the health of our people,” said Louisa McCovey, the Yurok Tribe Environmental Program director, in an exhibit film clip called “Salmon Sanctuary.”
“We are connected to this place. We care about it and we’ll do anything to protect it,” she said.
Earlier this year, the Yurok Tribe, with assistance from the Western Rivers Conservancy, reacquired a large tract of land in the Blue Creek watershed, one of the Klamath’s most important tributaries. The creek, which better resembles a river, contains prime spawning and rearing grounds for salmon steelhead trout and other fish species, the press release said. The tribe is working toward turning Blue Creek — where there is a history of industrial logging — into a salmon stronghold and returning its forests back into an old-growth, biodiverse ecosystem. This project is a primary theme in another “Giants of Land and Sea” video.
“The Yurok Tribe encourages everyone to visit the California Academy of Sciences to take advantage of the opportunity to deeply immerse in Northern California’s rich, natural heritage,” James said.
The museum is located in Golden Gate Park at 55 Music Concourse Drive.
A little water could make a big difference for endangered salmon
June 5, 2018
Even small amounts of running water--less than a gallon per second--could mean the difference between life or death for juvenile coho salmon in coastal California streams, according to a new study published in the journal Transactions of the American Fisheries Society.
The study, led by California Sea Grant Extension Specialist Mariska Obedzinski, shows that during dry periods, that amount of water was enough to keep pools interconnected, allowing young salmon to survive through the hot, dry summer months.
"The good news is that if we can get just a little bit of water back in these streams, we can make a really big difference," says Obedzinski, who leads a monitoring program for endangered coho salmon and steelhead in the small streams of Sonoma County that flow into the Russian River.
Saving the Russian River coho
Russian River coho salmon were listed as threatened in 1996, but despite efforts to improve habitat, the species had hit crisis levels by the early 2000's, and they became endangered in 2005 when scientists noted fewer than 10 fish returning to the Russian River each year to spawn. In response, local, state, and federal agencies teamed up to start a conservation hatchery program to breed and release the fish. California Sea Grant's monitoring program was set up to track the success of the hatchery releases as well as better understand the factors that were preventing recovery of the species.
Through their monitoring, Obedzinski and her research team found that low streamflow in summer is one of the biggest bottlenecks to coho recovery. She says, "After the hatchery fish are released, we see them migrating out to the ocean and coming back as adults to spawn. We even see their offspring in creeks in the early summer, but by late summer the creeks dry out, the young salmon die, and the next generation is not surviving."
How much is enough?
Water is a limited resource in the Mediterranean climate of central California. Population growth and development, combined with the impacts of climate change in the drought-prone region have made flow-impaired streams even less reliable.
While previous modeling studies have established water flow thresholds to support salmon in larger, snowmelt-fed streams such as those in California's central valley, the small coastal streams where Russian River coho prefer to spawn are a different beast.
These intermittent streams may swell over their banks during wet winter months but dwindle to a trickle or even dry up in sections during the hot, dry summer. While it was clear that young salmon needed more water to survive the summer months, the question was, how much?
"We didn't have a sense of how much water was needed," says Obedzinski. "The existing models are based on flows in much larger streams. When you try to apply them to our tiny coastal streams, they fall apart."
The new study provides a clearer link between salmon survival and water flow rates in Russian River tributaries, which could be useful for resource agencies and organizations working on salmon recovery, and land owners who want to help restore endangered salmon populations. The findings may also lend support for efforts that might seem small-scale in comparison to larger streamflow improvement projects in other watersheds.
John Green is a project manager for the Gold Ridge Resource Conservation District, who has already begun applying the new research to their work restoring flow in salmon streams. He says, "The big value in this research is that it has given us an idea of how much water is needed to improve fish survival. From that, we start to understand the kinds of projects we need to build and what their impacts will be."
The researchers stress that flows allowing for minimum persistence are not high enough to support full recovery. Obedzinski says, "Keeping a pool connected is the first step in preventing local extinction by keeping at least some of the fish alive, but we want fish to be able to grow and thrive as well. In terms of meeting recovery targets, more water means more habitat for fish, and more chance of bringing back a healthy population."