They were carried in pairs, sloshing around inside Yeti coolers, from a water tank truck idling in the Muir Beach parking lot to the muddy shores of Redwood Creek. Volunteers used wheelbarrows to transfer them to biologists who hoisted them into the creek using nets.
After a couple of hours, 188 adult coho salmon were released into the creek, where they paused before traveling upstream. Locals lined the pedestrian bridge to cheer them on.
The fish, plucked as juveniles from this exact location in 2014, were reared at the Warm Springs Hatchery in Lake Sonoma. Now they’re ready to return home and, to the delight of the dozens of biologists and others present at the release, engage in fruitful spawning.
Since 2014, several federal, state and local agencies have collaborated to harvest and release coho into Redwood Creek in hopes of boosting the endangered population. In a written statement, the state Department of Fish and Wildlife said the long decline of coho in the creek has been “accelerated by recent periods of poor ocean survival combined with the prolonged California drought.”
In the years leading up to this effort, fewer than 10 adult coho salmon were estimated to have returned to the creek to spawn.
Coho are anadromous, which means they return to the freshwater streams in which they were born in order to procreate. But unlike other Pacific salmonids, coho spend an extra year as juveniles in their freshwater origins, exposing them to dangers caused by habitat degradation and poor water quality. Then, if and when they make it to sea, they are confronted with predators and pollutants.
Biologists believe that removing the ocean phase in their lifecycle is essential for rejuvenating populations.
Coho populations have dropped not just in Redwood Creek, but across West Marin and statewide. Since the early ‘90s, all commercial and recreational fisheries for coho were closed, and the species was listed as endangered.
According to Eric Ettlinger, an aquatic ecologist with the Marin Municipal Water District, coho in the nearby Lagunitas Creek have averaged about 300 adults in the last decade, compared to anecdotal observations of over 5,000 in the early ‘60s.
This is the second consecutive year that coho were returned to Redwood Creek—last year’s release numbered at 106 salmon—and the project will be repeated for one more year.
Each participating agency has a defined role: Golden Gate National Parks Conservancy corrals dozens of volunteers, a scientist from NOAA’s National Marine Fisheries Service studies collected tissue samples and biologists from both the California Department of Fish and Wildlife and the National Park Service oversee the captive breeding program.
“The biggest source of death for salmon is the ocean,” Darren Fong, an aquatic ecologist with the Golden Gate National Recreation Area, said. “They have a less than 1 percent survival rate, while this method has over 80 percent survivorship.”
Mr. Fong acknowledged that it’s an upstream battle for reviving coho populations in Marin, but optimism was tangible last Friday.