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Coho Salmon Back from the Brink

coho salmonEndangered coho salmon rebound in Scott Creek

A few miles north of Davenport, Scott Creek winds through steep coastal mountains that time forgot, past old farmhouses, redwoods and pines.

A rare Bay Area watershed spared from development, the creek has become the front lines of the fight to save the endangered Central California Coast coho salmon, where the federal government, the California Department of Fish and Wildlife and a nonprofit fish hatchery have partnered to pull the fish from the brink of extinction.

If these coho salmon were to stage a comeback anywhere south of the Golden Gate Bridge, it would be in Scott Creek, says Erick Sturm, research fisheries biologist with the National Oceanic and Atmospheric Administration (NOAA), a federal agency.

Hundreds of thousands of coho once swarmed the waters between Humboldt County and Santa Cruz, enough to be fished with pitchforks, according to the NOAA website. But development, logging, overfishing, climate change, water diversion, and other factors led to their decline, from around 99,000 statewide in the 1960s to 6,000 in the 1990s, Sturm says. The fish was federally listed as threatened in 1996, then as endangered in 2005.

In 2009, fewer than 500 Central Coast coho lived in the wild, and this past May, NOAA listed it as one of eight ocean species most at risk of extinction.

Scott Creek is at the southern border of the coho’s range, where the species is vulnerable, says Sturm.

“They’re living life on the very edge, so that’s somewhat difficult for them,” Sturm says. “And historically, because you’re on the southern edge of their run the disturbances in their natural habitat, be it natural or manmade, can really have a greater effect on their life cycle.”

 

Turning Tide

In lower Scott Creek, a NOAA fish monitoring station counts the coho each rainy season.

The fish follow a three-year cycle. Eggs are laid in the creek in winter and hatch in the spring. Juveniles spend a year in freshwater, then swim to the ocean, spending a year or two there before returning to the creek to spawn and die.

In 2002, 400 spawning adult coho returned to Scott Creek, a figure that dropped to 330 in 2005 and 11 in 2008. In 2011, only three adults were counted.

But thanks to a breeding program led by NOAA, the California Department of Fish and Wildlife and local hatchery nonprofit Monterey Bay Salmon and Trout Project, the fish are making a resurgence.

Last winter, around 150 spawning adults returned to the creek, the highest number in a decade.

What’s more, this fall NOAA divers counted around 7,000 juvenile coho in the creek, a high number considering this summer was the fourth summer in a drought.

“We hope we’ve turned the corner and we’re on the upward trajectory on the species, but we need another two or three years to tell,” Sturm says. “As far as delisting, we’re nowhere near that.”

To be considered no longer endangered, not only does Scott Creek need a 12-year average of more than 500 spawning adults each winter, but 27 other watersheds farther north to Humboldt County need similar gains.

 

Scale of a Tale

Six miles north of Davenport, along a wooded tributary of Scott Creek sits the Monterey Bay Salmon and Trout Project’s Kingfisher Flat Hatchery, where around a dozen tanks hold thousands of young coho raised on-site.

Since 2002, the volunteer-run hatchery has led a coho breeding program supported in part by NOAA and state fish and wildlife. In the last two years the hatchery has released around 40,000 juvenile coho in Scott Creek.

Mark Galloway, the hatchery’s manager, points to an incubator which will house around 130,000 fertilized eggs this winter.

“It’s like a fridge,” he says. “The eggs like it cool and it uses very little water.”

When the eggs hatch and develop eyes, they are moved to water trays covered with screens.  Over the following weeks, the tiny fish slowly digest the yolk sack bulging from their abdomens until they start nosing the screen, hungry for real food.

As the fish grow, hatchery staff and volunteers move them to larger tanks, until eventually at one year old, they are tagged and released in Scott Creek.

Outside, Galloway flung food pellets into the hatchery’s two largest tanks, each holding 10,000 fish destined for a carefully timed release this spring. As the fish head to the ocean, it’s crucial that their food source—seasonal krill fueled by wind-driven ocean upwelling—is there to meet them.

“If that upwelling current is not generated and their food source crashes, the population will crash,” Galloway says.

In 2017, the hatchery hopes to increase its release numbers by 10,000 fish, thanks to a new system completed recently, built mostly by volunteers and funded by the state, that allows it to return water to the creek. Until now, the drought levels in the creek have been the hatchery’s biggest limitation, since creekwater is used for all the tanks.

Another key part of the program is the captive broodstock—around 400 fish culled from each year’s batch, genetically selected to remain at the hatchery and artificially spawn the next generation.

To check for sexual maturity, each of these 400 fish is individually anesthetized and scanned with ultrasound, similar to a pregnant woman in an obstetrician’s office.

Without the hatchery program and biologists’ devotion, the coho would be extinct, says Galloway. Only the Russian River in Sonoma County has similar resources devoted to the coho.

The record numbers of spawning adults returning to Scott Creek last winter were all tagged and released by the hatchery two years prior.

“The key is that they were able to spawn voluntarily,” says Galloway. “They didn’t need our help to find a habitat or choose a mate. The drought conditions probably did affect their survival somewhat. The creek dried up, but it didn’t prevent the significant production that federal survey crews found.”

 

From the Banks of Scott Creek

Unlike the San Lorenzo River, which has thousands of private landowners along its banks, Scott Creek is sparsely populated, making it some of the best coho habitat south of the Golden Gate Bridge.

But the creek isn’t exactly untouched, and more can be done to improve the coho’s chances, says Jon Ambrose, salmon reintroduction coordinator at NOAA.

At the creek’s mouth, a Highway 1 bridge built in 1939 straightened the creek, damaging an important estuary where coho once fed. Talk of replacing the bridge and restoring the lagoon began more than a decade ago, but funds are still being sought.

Also, in recent yearsCalifornia Polytechnic State University, which owns and manages the lower section of Scott Creek, led important restoration projects.

Levees built in the 1940s and 1950s meant to prevent flooding only prevented fish from accessing floodplains during winter storms. To improve coho winter survival, the campus breached the levees.

In the last 35 years all large trees were removed from lower Scott Creek, which halted the formation of deep pools next to fallen logs—key for maintaining large coho populations.

The university anchored large logs in the stream, directly making fish habitat and further keying the coho’s survival.

Ambrose says it’s not just one thing, but many interacting factors upstream that impact the coho.

What’s important for people to know, he says, is that there’s hope.

“That little hatchery, a little bit of habitat restoration, a little bit of oversight by the county, and the regulatory agencies are making a difference,” he says. “If we really put our backs into it, we can really bring this fish back.”


ALL GROWN UP Erick Sturm, NOAA research fisheries biologist who helps to scan fish with ultrasound, holds a large Central California Coast coho salmon. PHOTO: MARK GALLOWAY

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