A new fish ladder on Auburn Ravine in Placer County is proving its value for salmon returning from the ocean to spawn.
Biologists with the California Department of Fish and Game say 150 fall-run chinook salmon have surmounted the ladder near Lincoln in the past three weeks. Officials have also counted 13 spawning sites, or redds, in the gravel creekbed upstream of the ladder.
"That ladder is a godsend and it is working very well," said John Rabe, a board member of Save Auburn Ravine Salmon and Steelhead, a nonprofit that has worked for more than three years to restore salmon in the creek. "It really exceeds anything we had dreamed of in our wildest dreams."
Auburn Ravine is one of hundreds of small Sacramento River tributaries that once hosted salmon runs. Today, the creek enters the Sacramento River via the Natomas Cross Canal, a flood-control channel. It then winds for miles through small farms and suburbs outside Sacramento, Roseville and Lincoln, finally reaching the Sierra Nevada foothills near Auburn.
The creek in recent years has been blocked by numerous small agricultural dams which, by law, must be removed in the fall for fish passage. This obligation has not always been met. Rabe's group has helped educate landowners about clearing these barriers each year.
The group also persuaded the Nevada Irrigation District to install the fish ladder at its Lincoln Gauging Station,and helped raise money for the project. The gauging station, a flow-measuring device built in 1981, was a solid concrete wall, about 6 feet high, that spanned the ravine.
A few hardy salmon could usually surmount the wall each year. But it was a barrier to most fish.
The irrigation district built the fish ladder in 2011 at a cost of more than $800,000. It paid $250,000 toward the job. The rest came from Placer County, state and federal agencies, and nonprofit groups.
"The work they did out there did a tremendous job to bring salmon farther upstream," said Mike Healey, a staff environmental scientist at Fish and Game who was counting salmon and surveying habitat along the ravine on Friday. "It's a surprise to see salmon above the Lincoln Gauging Station, because that had been a pretty good barrier at lower flows."
The ladder's success reinforces the importance of small streams to restoring Central Valley salmon, Rabe said. His group is working to next construct a fish ladder at Hemphill Dam, a much-larger barrier farther upstream. It will be more expensive, but the Nevada Irrigation District has been supportive of the project.
It will also be important to ensure enough water flow in the creek to sustain young salmon. They will hatch in about one month, Healey said, and the juvenile salmon will begin to migrate toward the ocean a few months later.
Winter rains ought to provide enough flow to sustain the fish in normal years. But in dry years, water agencies might have to release additional water from dams upstream to protect the fish.