A Sacramento State geology professor and a team of students are playing a critical role in the ambitious – and successful – federal and state efforts to rehabilitate the American and Feather rivers and increase the salmon population.
The Sac State team monitors the minerals in what’s known as the “salmon gravel project.”
Legend has it that salmon once were so abundant in the American River that early Miwok Indians could walk on fish from bank to bank and never get their feet wet. That isn’t quite true, says Professor Tim Horner, who also chairs Sac State’s Department of Geology, but salmon certainly were more plentiful in the past.
“The rivers have changed, and the fish aren’t doing so well,” Horner says. “We’ve seen some really big declines over the last 50 years. It got to the point we were afraid of extinction in some rivers. The populations were so low six or eight years ago that we were worried about where things were going.”
The trouble was that the rivers no longer had the proper gravel for spawning.
“Salmon bury their eggs in the rocks and need gravel about the size of marbles and golf balls, but a lot of that finer material has been swept away by big floods and flows since the dams were put in,” Horner says. “The rivers have changed. We’re left with bowling ball-size rocks that the fish can’t move around to bury their eggs, and that’s a problem.”
Sac State partners with variety of agencies, including the U.S. Bureau of Reclamation, the U.S. Fish and Wildlife Service, the National Oceanic and Atmospheric Administration Fisheries, the California Department of Fish and Wildlife and the Sacramento Water Forum, along with hydraulic and civil engineers and fisheries biologists.
The students, most of whom are geology majors, help with the planning and design of new fish habitats. Once a river site is selected, bulldozers and front-end loaders remove the oversized rock on a quarter-mile stretch of river bed and replace it with suitable gravel placed at the correct depth to create a pleasing riffle for spawning salmon.
Since 2008, Sacramento State and its partners have created six new fish habitats between Nimbus Dam and River Bend Park on the American River. The Sac State team also monitors five sites on the Feather River, with plans to add new gravel to three of those habitats next summer.
So far, the results of this work have been astonishing, Horner says.
“We have a lot of information about how many fish spawn at each of these sites. We get that from a series of air photographs. The Bureau of Reclamation hires a contractor to fly over the river and take low-level photos that are of such high quality that you can see individual salmon nests, or redds,” he says.
A year before the first habitat was rehabilitated at Sailor Bar, adjacent to the Nimbus Fish Hatchery, aerial photos showed fewer than 30 spawning salmon. But within a few weeks of the new gravel’s installation, the fish count had multiplied tenfold.
“It was a night-and-day difference,” Horner says.
He and a group of students were on the American River recently to evaluate two sites near Sailor Bar, a Sacramento County park. They tested the depth of the gravel and the velocity and oxygen levels of the water, all the while surrounded by hundreds of salmon.
“Salmon are an integral part of our heritage,” says Katy Janes, who will graduate in December with a master’s degree in geology. “As scientists, we are restoring specific parts of this river to bring those populations back. Salmon are a proxy for the health of our rivers, and we’re helping to bring them back to their full glory.”
The team’s efforts on behalf of salmon also help steelhead, which have similar needs. Steelhead are considered “threatened” under the federal Endangered Species Act. Salmon are not listed despite their declining numbers.
The salmon gravel project is a perfect training ground for students because it allows them to work on real-world problems, Horner says.
“We’ve had funding since 2002 that supports students – usually geology majors and a few from other departments – and I usually have master’s students who are working on their thesis project,” he says. “They are the project managers. I just watch it all happen when we get out there.”
For media assistance, contact Sacramento State’s Office of Public Affairs at (916) 278-6156. – Dixie Reid