DENVER, March 13 (UPI) -- The endangered coho salmon of Tomales Bay, north of San Francisco, are getting assistance from a stream restoration effort that could help rescue them from near-extinction locally.
Through the project, fish ecologists hope they can restore habitat to rebuild decimated populations of the historic fish, which once was a staple of indigenous diets and later California commercial fishing.
Central California coast coho salmon formerly were plentiful on the West Coast, but the population has shrunk so low that the fish is listed as endangered in California, Oregon and Washington under the federal Endangered Species Act. It is now illegal to catch coho salmon in California. Cohos are not protected in Alaska.
The fishes' spawning grounds are becoming hard to find. Unlike Chinook salmon, which lay eggs in rushing rivers, coho prefer small streams.
Where once the coho spawned in almost 600 natural small streams and rivers in California, that habitat has now mostly disappeared. Most small tributaries have been encroached by housing development or dammed for drinking-water reservoirs.
Still, the cohos are beloved in the region. In the Lagunitas Creek watershed, tourists come from San Francisco and beyond to watch the salmon run every winter along the stream beds. The fish swim 26 miles upstream from the ocean to spawn in December and January.
"They're big fish, 24 to 30 inches, in their red spawning colors," said Chuck Schultz, a member of the local Golden Gate Trout Unlimited chapter.
During the yearly salmon run, the fish leap up a series of waterfalls called the Inkwells, "about 6 or 7 feet in the air," Schultz said. "Seeing a big fish like that in a small stream is really something."
Usually, about 400 to 500 leaping coho make the annual trip to the spawning grounds, but this year's numbers were dangerously small, with fewer than 90 fish making the trek -- among the lowest counts in 25 years, according to the Marin Municipal Water District.
"We've seen the coho population bounce back after disappointing runs and we're hopeful that improving ocean conditions will mean higher returns in coming years," said Eric Ettlinger, aquatic ecologist for the water district.
This summer, earthmovers will remove the remnants of a man-made fish barrier, possibly making it significantly easier for cohos to return to their spawning grounds in west Marin County.
"Historically, there were thousands of these fish, and the numbers are now dismally low," said Todd Steiner, executive director of the Olema-based Salmon Protection and Watershed Network. More than 95 percent of their population has been lost, said Steiner, a wildlife biologist.
In June, the network and the California Department of Fish and Wildlife will create a new path for coho in the San Geronimo Creek, which runs through a shuttered golf course north of San Francisco.
A concrete and metal structure called Roy's Pools will be replaced by a $2 million project that will create a free-flowing channel for the salmon, as well as steelhead trout and other stream wildlife. Volunteers also will replace native plants, including redwood seedlings. A visitor bridge will allow fish viewing.
The life of the wild coho is a round-trip journey between fresh and ocean waters.
The fish live for three years. As juveniles, they grow to about 3 inches long in freshwater streams, and then make the trek through the bay to the Pacific Ocean, where they grow to 2 feet long and with weights of 8 to 10 pounds
They make one trip back to their birthplace to spawn and die. Wild coho will not mingle or breed with fishery-raised coho salmon that are stocked in other local river habitats.
Still, the restoration project alone might not be enough to restore the coho population, the salmon group's Steiner said.
"We're taking down a tiny dam, not big at all, but it is one of the only streams left for coho to reach the headlands," Steiner said. "We may not be able to bring them back from brink of local extinction. The science of habitat restoration is new, and we learn every time we do a project. There are no guarantees in this line of work."