NOAA partners The Nature Conservancy and Trout Unlimited report that endangered Central California Coast coho salmon are using NOAA-funded restoration sites. This coincides with a record-breaking spawning season.
By NOAA Fisheries
Thanks in part to NOAA’s 20-year investment in this species, Central California Coast coho salmon returned to Mendocino rivers and streams in record-breaking numbers last spawning season. Fish returning to these sites are bigger and healthier than other fish in the watershed.
NOAA’s Office of Habitat Conservation funds habitat restoration projects benefiting the endangered Central California Coast coho salmon and steelhead on the Mendocino Coast. In 2023, it awarded The Nature Conservancy and Trout Unlimited $14.5 million through the Infrastructure Investment and Jobs Act for projects being implemented over the next several years.
We recently checked in with our Mendocino Coast partners to ask how their work is progressing. They report that juvenile CCC coho salmon and steelhead have moved into recently restored habitats, including one where coho have been absent for 70 years or more.
The Nature Conservancy: Building Underwater Apartment Complexes for Coho
NOAA’s Office of Habitat Conservation is currently funding four The Nature Conservancy (TNC) restoration projects in the Ten Mile, Garcia and Navarro River watersheds.
Over the last 6 years, TNC has focused on restoring winter habitat for juvenile CCC coho salmon on the lower Ten Mile River. So far, the coho seem to like their new digs. “We’ve seen robust use of our restoration sites,” says Peter van de Burgt, North Coast Restoration project manager for TNC. “We’re also seeing that the fish using the sites are growing much faster than fish that aren’t. They’re fitter and better able to survive.”
The Ten Mile River saw record-breaking returns of CCC coho salmon over the 2023-2024 spawning season. The river surpassed its NOAA recovery target of 3,700 fish for the first time. If a longer term upward trend is established in multiple watersheds, CCC coho could be removed from the endangered species list.
Like other Mendocino rivers, Ten Mile lacks the type of habitat juvenile fish need to survive California’s climate extremes. Juvenile coho reside in freshwater for a year or two. They must persist through warm summers when streams may dry into a series of disconnected pools. During the winter, storms cause streams to swell into raging torrents. Young fish must be able to escape to slow-moving side channels and floodplains to avoid being swept out to sea. Coho also fatten up when they can eat terrestrial bugs in floodplain habitats. The bigger they are, the better the chance of their survival in the ocean.
“Studies indicate that only 5 percent of the historic winter habitat for salmon is still available,” says van de Burgt. “Winter habitat is usually functioning wetlands and floodplains, and it’s almost all gone now.”
In addition to rivers and streams being cut off from floodplains, much of the watershed lacks the stream complexity juvenile coho need. In a healthy redwood forest, streams would be crisscrossed with old tree trunks, root balls, and other woody debris. However, the massive old redwoods and fallen trees were removed in the last two centuries due to logging and other human activities.
“A stream without wood might be 6 inches deep, but when you have a huge tree in the water, it creates scour that can make the stream 6 or 8 feet deep,” says Jonathan Ambrose, NOAA Fisheries’ San Joaquin River Ranch branch chief. “The fallen tree creates something like an underwater apartment complex that can provide habitat to many more individuals than a shallow stream.”
Now, TNC and other partners like Trout Unlimited (TU) are putting wood back in the rivers and reconnecting floodplains to recreate healthy winter habitats. In June 2025, TNC will begin construction on its biggest ever restoration project on the Ten Mile River with NOAA funds.
“We will restore floodplain and instream habitat at a large scale along a critical section of the Ten Mile River,” says van de Burgt. “Implementing a project of this size makes a real difference in landscape-level habitat availability for coho, especially during the winter season.”
“This wouldn’t be possible without our partnership with NOAA staff,” says van de Burgt. “The assistance they provide goes way beyond funding. We consult with them from the very first idea of a project through planning, engineering, design, permitting, and implementation.”
Trout Unlimited: Salmonids Access Barrier Removal Site for First Time in Decades
Several years ago, NOAA staff members watched as an adult steelhead frantically tried to swim upstream at Dry Dock Gulch. The gulch is an offshoot of the lower Big River on California’s Mendocino Coast. Two undersized road culverts providing upstream access were perched impossibly high above the 4-inch-deep stream. The steelhead turned around and disappeared with no way forward to escape the harbor seal chasing it. Poorly designed road-stream crossings like the one at Dry Dock (and other stream barriers) threaten the survival of Northern California steelhead and CCC coho. These species need to be able to migrate up and down streams to spawn, escape predators, and rear as juveniles.
Anna Halligan, North Coast coho project director for TU, visited Dry Dock in the fall of 2023. The old road culverts had been replaced with a 10-foot-wide, 68-foot-long aluminum culvert with NOAA funding. Remarkably, the same scene NOAA staff witnessed earlier repeated itself: A battered steelhead with a seal in hot pursuit swam up to the culvert. Only this time, the steelhead made it through. Moreover, the TU monitoring team found a juvenile CCC coho above the new culvert.
“It’s possible fish have not had access to habitat above the culvert in 70 to 100 years,” says Halligan. “We worked on planning and design for 10 years, and it’s reassuring and exciting to see the fish respond as we had hoped.”
During the 2023–2024 monitoring season, teams caught 315 juvenile coho using the restored alcove and stream at Dry Dock. Some tagged juveniles were caught repeatedly and grew in size throughout the winter. At the start of the 2024–2025 monitoring season in November, a team found some of the same coho using the site, and a few newcomers.
NOAA’s Office of Habitat Conservation funds the Dry Dock project and six other barrier removal projects with TU. These projects improve access to historic spawning and rearing habitat as well as provide durable road infrastructure that benefit local communities.
This past summer, TU removed an 18-foot-high earthen dam and restored 1,600 feet of stream channel at Neefus Gulch, a North Fork Navarro River tributary. This project and a previous NOAA-funded effort to remove a nearby culvert opened up 1.3 miles of CCC coho and steelhead habitat.
On December 6, 2024, a TU team spotted the first juvenile steelhead using habitat above the old dam site. Like Dry Dock, salmon had not used this area in 70 years. Later, on January 6, TU Project Manager Nicole Herrara observed a female coho within the restored channel reach. They surveyed the channel and found 17 salmon nests in Neefus Gulch, including four above the project area.
In 2025, the TU team plans to address barriers at Duffy Gulch, part of the Noyo River watershed, and Cooper Mill Creek, a sub-basin of the Eel River.
“The NOAA Restoration Center is excited to share the results of these endangered fish recolonizing old habitats and using new habitats thanks to The Nature Conservancy, Trout Unlimited, and our other partners,” said NOAA Marine Habitat Restoration Specialist Joe Pecharich. “Teamwork makes the stream work.”
