Salmon, steelhead spawn freely in restored American River gravel

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Technician Liz Smith, left, and biologist Ben Rook survey a school of chinook salmon fry Thursday on the American River dowstream from Nimbus Dam in Rancho Cordova.​

New fish spawning areas in the American River are bristling with fresh nests of steelhead eggs – so many that officials urge anglers and others not to wade in the area.

Salmon and steelhead breed by laying eggs in riverbed gravel. They use their powerful tails to sweep out circular nests in the gravel to hold their eggs.

Appropriate gravel is in short supply, however, due to a century of dam building, mining and other activities.

To address this problem, hundreds of truckloads of gravel were spread in two riverbed areas just downstream from Nimbus Dam over past the two years in a joint project by the Sacramento Water Forum and U.S. Bureau of Reclamation.

The project has succeeded in coaxing more fish to lay eggs in the American River. Salmon and steelhead have created at least 347 gravel nests – also called "redds" – in the restored areas, according to surveys by Cramer Fish Sciences, a consultant hired to monitor the project.

Joe Merz, a senior scientist at Cramer, said the salmon and steelhead redds counted this year could produce nearly 800,000 young fish.

Walking through those redds, however, could crush the eggs or cause them to be dispersed before they hatch.

"Trampling all over the redds may help (anglers) get to fish this year, but if they are killing the eggs, there may not be as many fish in years to come," said Sarah Foley, deputy director of the Water Forum.

The agency asks people not to wade through the area at least through April, when steelhead hatch. New signs along the river help point out areas to avoid.

Historically, small gravels washed out of the mountains with river flows to continually renew spawning habitat. The construction of dams blocked this movement, causing gravels to be depleted or clogged with sediment.

In 2008 and 2009, the project added 17,500 tons of fine gravels to two large areas adjacent to the Department of Fish and Game's Nimbus Hatchery and Sailor Bar recreation area.

The two projects, funded by the Bureau of Reclamation to atone for the dams' negative effect on fish populations, cost about $750,000.

Increasing the number of wild-spawning salmon and steelhead is considered important to the survival of those species. Recent research suggests most of the salmon in the Central Valley are hatchery fish, which are considered less resilient.

Reclamation and the Water Forum plan to add more gravel in a third location on the river later this year.

John Montgomery, left, Jesse Anderson, Liz Smith and Ben Rook assemble data on the American River on how fish use recently spread gravel to build nests.​

Fisheries biologist Jesse Anderson navigates the American River just downstream from the Nimbus Fish Hatchery. Scientists say that salmon and steelhead nests, or "redds," counted this year could produce 800,000 young fish.​

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