WATERS.BEST

Muir Woods launches endangered salmon restoration project

 by WILL HOUSTON | whouston@marinij.com | PUBLISHED: July 31, 2023 by Marin IJ

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Researchers Tim Smoot, left, and Bentley McNeill work to capture and relocate fish

as part of a habitat restoration project at Redwood Creek in the Muir Woods National Monument on Tuesday, July 25, 2023. (Sherry LaVars/Marin Independent Journal)

Visitors at Muir Woods National Monument will see more construction work than usual this summer as the National Park Service undertakes a habitat restoration project for endangered coho salmon.

The agency aims to restore 750 feet of Redwood Creek through the popular redwood forest. The project is intended to rectify the damage caused by work performed during the 1930s.

At the time, the Civilian Conservation Corps was reshaping the park, including adding a new trail network, as part of President Franklin D. Roosevelt’s New Deal. To prevent flooding and erosion that could damage trails and redwood trees, the corps built rock walls along the banks of Redwood Creek to stabilize it.

While well-intentioned at the time, the alterations disrupted the natural habitat and cycles that coho salmon and other species need to reproduce. The rip-rap walls impaired the creek’s ability to meander and create floodplains during storms, leading to swift currents that damaged habitat and washed away young fish.

The removal of logs from the creek led to fewer pools where newly hatched salmon could take refuge from predators and the fast winter flows during their 16-month rearing period in fresh water.

Park crews are winding back the clock by removing the rock walls and placing large logs in the creek to rebuild the natural habitat.

“What we are seeing is management has to change and evolve over time. We have better information and data now,” said park ranger and site supervisor Jules Cooch. “We’re managing for the whole ecosystem, not just the redwood trees but for all of the species in the ecosystem.”

Marin County is home to the largest population of Central Coast coho salmon from Monterey Bay to the Sonoma-Mendocino County line, with Lagunitas Creek holding the most. Redwood Creek has historically had salmon runs, but now only has a handful of spawners return each year.

The $1 million project is the second phase of Redwood Creek restoration as part of the “Redwood Renewal” project. Launched in 2017, the project also aims to protect sensitive habitats by relocating and enhancing trails, bridges, parking lots and wastewater systems in the national monument.

A map of the National Park Service’s Redwood Renewal project in Muir Woods National Monument. (Provided by the National Park Service)

In 2019, the park completed a separate $1 million project to restore about a third of a mile of the creek, according to project manager Carolyn Shoulders.

The second phase will restore another 750 feet just downstream closer to the park entrance. Crews will remove 510 cubic yards of rock from the creek — enough to fill about 35 dump trucks — and put it to other uses in the park, according to Cooch. The project will also remove about 400 feet of asphalt trail.

Both projects are fully funded by park entrance fees, according to Shoulders.

National Park Service biologist Mike Reichmuth said this section of the creek is ideal habitat for spawning and rearing coho salmon.

“Because you have the redwood trees, it keeps it nice and cool with the shading that goes on,” Reichmuth said. “Even in drought years, it usually maintains flow in that section of the creek compared to lower down in the watershed where there is less forest canopy, and sometimes we see drying during the summertime.”

The restoration work has shown success so far, Reichmuth said. Following the torrential downpours that occurred this past winter, Reichmuth said surveys conducted this summer found young coho salmon residing in deep pools where before they would have likely been washed downstream.

“They gave them that refuge from the high flows,” Reichmuth said.

But working in a habitat that is home to protected and endangered species requires meticulous work before heavy equipment can be used. In the first weeks of the project, Reichmuth and other staff worked to capture more than 1,500 critters, including juvenile coho salmon, steelhead, sculpin and others for relocation to pools in other areas of the creek.

The section of creek will be drained and diverted using a pipeline to allow for construction crews to move in but still maintain the creek’s flow, Cooch said.

Reichmuth said the initial approach is to use seine nets, which capture the majority of the animals. For species that are left behind or harder to catch, biologists can use a tool known as a backpack electrofisher. Resembling the proton pack from the “Ghostbusters” movie, the device allows a surveyor to place a metallic probe in the water to create an electric current.

“You put a current in the water and once the fish get within a couple of feet from this probe they are actually drawn toward the probe,” Reichmuth said. “Then within a foot, they are briefly stunned. It’s pretty quick. You don’t have a fish that’s floating on the top of the water. It’s just enough time for someone to take a net and scoop them.”

Cooch said crews are also focused on potential impacts on the life around the creek. As part of the project, crews are salvaging plants in the project site and cultivating native plants at a nursery in the Marin Headlands. About 3,000 plants will be placed at the site at the end of the project, Cooch said.

The project will result in a closure of one bridge and a temporary closure of Bohemian Grove, with alerts being posted on the park’s website.

“A lot of management that happens in the National Park Service we try to do in ways that visitors don’t see because we don’t necessarily want to impact their visit,” Cooch said. “However, this is one that is such a great opportunity for people can see conservation in action.”

More information about the Redwood Renewal project can be found at nps.gov/muwo/getinvolved/redwood-renewal-begins.htm

Photo courtesy, Aldaron Laird