Nimbus Hatchery on the American River trapped 2,281 steelhead this season as drought continues

Anglers fish the American River below Nimbus Fish Hatchery on the opening day of steelhead season of 2022. Photo by Dan Bacher. | 

By Dan Bacher | 

GOLD RIVER - Nimbus Fish Hatchery, located on the upper section of the Sacramento Metropolitan Area’s crown jewel, the American River, has finished spawning steelhead for the season. The run was relatively robust this season, although steelhead fishing has been poor for most anglers as the record drought continues in California.

 “Steelhead seem to have enjoyed climbing the new ladder--we collected 2,281 fish this year; more than 3 times what we saw last year,” reported Gary Novak, hatchery manager, referring to the new hatchery ladder that went into operation in November 2021.  “Now that spawning has finished, the fish ladder has been drained and will remain empty until the salmon return in the fall.”

During the best years the hatchery has seen since Nimbus and Folsom dams were built, steelhead counts at the facility have numbered from 3,000 to 4,000 fish. 

The hatchery staff this year had no problem in gathering enough eggs to reach their annual production goal of 430,000 steelhead yearlings that are released into the river in January and February every year.

Despite the comparatively high numbers of steelhead this season, fishing has been tough for most fishermen, due to clear water conditions on the river for most of the season. 

Before the Gold Rush and the genocide of the Nisenan (Southern Maidu) and Miwok Tribes in the region that ensued, the steelhead and salmon runs on the American River likely numbered in the millions or hundreds of thousands. After Folsom Dam was built and before Folsom and Nimbus Dams were finished, much smaller numbers of native steelhead passed over Old Folsom Dam’s fish ladder every month of year except August and September and the run peaked in May or June.  

The completion of Nimbus Dam in 1955 and Folsom Dam in 1956 prevented native salmon and steelhead from reaching most of their historic spawning areas in the main river and the river’s north, middle and south forks and tributaries. The Bureau of Reclamation, the agency that built the dams, also built and funds the Nimbus Fish Hatchery to mitigate for the loss of spawning habitat.

After Nimbus Fish Hatchery went into operation in 1955, the native runs of steelhead apparently did not adapt well to the new conditions found on the river. Only several hundred fish returned each year to the facility in the spring migration months of March, April, May and June.

Because of the small number of eggs collected, the CDFW introduced Eel River-strain steelhead to replace the native strain and those became the predominant strain of steelhead, “In 1958-1959, eggs from Snow Mountain Egg Collection Station on the Eel River were transferred to the hatchery,” wrote Dennis Lee, fishery scientist, in his blog. (   

“In 1956, James A. Hinze, the first manager of the Nimbus Fish Hatchery, prepared the hatchery annual report. He wrote some steelhead passed the city of Folsom every month of the year except August and September. The peak of the run occurred in May or June,” said Lee.

Later, the California Department of Fish and Game in their 1990 Central Valley Salmon and Steelhead Restoration and Enhancement Plan reported “American River spring-run steelhead was extirpated and the fall-run steelhead, which provided a fishery beginning in September in the American River, was severely decimated by Nimbus Dam”.

The steelhead on the American are now the largest strain of steelhead found in the Central Valley. Several Eel-strain steelhead in the 19-pound to 20-pound class were caught in the 1980s and 1990s on the American, including one weighing exactly 20 pounds that was caught by a client of guide Barry Watson on January 1, 1990.

The largest-ever steelhead/rainbow trout documented on the American was a 25.02-pound wild fish (weighed on a digital scale) caught below Nimbus Hatchery in February of 2002. The fish may have been a wild rainbow that washed over from Lake Natoma or a steelhead living on the abundant forage below the dam, but since it was considered a wild steelhead under CDFW regulations, the angler had to release it.   

“Nimbus seeks to perpetuate the Eel River strain of steelhead by only spawning returning, hatchery-origin fish,” according to the CDFW. “Unlike salmon whose life cycle ends at spawning, steelhead potentially can spawn over multiple years and are returned to the American River almost immediately after spawning at Nimbus.” 

Scientific data are collected before the fish are set free – measurements, scales and tissue samples – “to better understand and inform the management of the American River’s steelhead,” the CDFW noted.

The average size of steelhead on the American River before Folsom Dam was built was apparently larger in size than other Central Valley stocks, according to my interviews with one of the few anglers who fished the river below the Nimbus Dam.

The less abundant winter steelhead would average around 7 pounds, while the more abundant spring-run fish that ascended the river and its tributaries from March through June averaged 3 to 6 pounds before the construction of Folsom Dam. 

Those of us who fish the river in the spring from April to June have caught and released wild steelhead that could be the original strain of spring-run steelhead, but no genetic analysis of these particular fish has been ever done.    

Cliff Clifton, who owned Hilltop Grocery in Half Moon Bay before he passed away in the early 1990s, used to regularly fish in the forks of the American River above what is now Folsom Lake in the spring and summer. He reported catching and releasing lots of steelhead smolts, along with resident river rainbows and browns, during the 1940s before Folsom Dam was built.

Those of us who fish the river in the spring from March through June have caught and released good numbers of wild steelhead that could be the original strain of spring-run steelhead, but no genetic analysis of these fish has been ever done. 

“I have fished the American for over 40 years,” said Thomas Cannon, California Sportfishing Protection Alliance (CSPA) fishery biologist. “Spring run steelhead were my main target. I have caught hundreds of wild 2-6 pounders into June, including many on dry flies.” 

The steelhead in the American are among the fastest growing trout found in any watershed – but also suffer significant mortality during the summer from disease spurred by warm water conditions.

Juvenile steelhead, while living in the river over the summer, need a daily mean water temperature of 65 degrees F or lower, according to Rob Titus, CDFW Biologist, during a presentation that he gave at a Save the American River Association meeting back in December 2013.  Titus emphasized that 65 degrees is the limit, not a preferred temperature, with 76 degrees being the lethal temperature for steelhead.

Chinook salmon spawning in the fall need water temperatures below 60 degrees for spawning and 58 degrees for egg incubation.

He also documented how steelhead in the lower American River, the ones that anglers like myself love to catch, may be the “fastest growing trout” in the world.

“There is a lot of food in the American – the fish average a growth rate of.82 mm per day. They grow really well,” he said.

He contrasted a slide of steelhead from the American River with one from Secret Ravine Creek, a tributary of Dry Creek. Whereas the American River fish is plump and healthy looking, the fish from Secret Ravine looks skinny and undernourished.

However, the same relatively warm conditions American River steelies encounter every summer have spurred the outbreak, first documented in 2004, of an anal vent disease called “rosy anus” associated with water temperatures of 65 degrees and above. 

The bottom line? “We need temperatures of 65 degrees or less at Watt Avenue to protect steelhead,” said Titus. “We also need to enhance the coldwater pool in Folsom Lake to maintain biodiversity of Chinook salmon on the American River. Finally, we need to balance temperature needs of Chinooks and steelhead.”   

The next anadromous run of fish to arrive in the American this year after the steelhead will be the American shad, a member of the herring family introduced from the Eastern Seaboard in the late Nineteenth Century. Shad should start moving into the American in mid-April and should show in large numbers by Cinco de Mayo.

That run will be followed by the fall run of Chinook salmon from September through December. 

In 2021, a total of 15,115 adult fall Chinook salmon and 7,188 two-year-old “jacks” returned to spawn at the hatchery or naturally on the river. Fifty percent of the total fish were natural spawners.

However, this is just a fraction of the number of fish that returned to the American in the fall of 2002, when a total of 150,000 Chinooks returned to the system. 

Between 2002 and 2021, the American River provided an average of 18 percent of total Sacramento River fall-run Chinook salmon spawning escapement.

A major problem with the management of the American River for fish at this time is that Folsom Dam is the closest major reservoir to the Delta. Folsom and Nimbus Dam releases are frequently used by the U.S. Bureau of Reclamation to maintain salinity standards on the Sacramento-San Joaquin River Delta as agribusiness interests, such as the Westlands Water District and Stewart and Lynda Resnick, the biggest orchard fruit growers in the world, export water to grow almonds, pistachios and other crops in the San Joaquin Valley. In addition, the American River serves many water users in a metropolitan area of over 1-1/2 million people. 

There are too many demands on the American River – and not enough water because of the overallocation of limited water resources  – and the steelhead, salmon and other fish inevitably end up suffering. The continuing drought in the West, the worst in 1200 years, according to climate scientists, only adds to the dilemma that we currently face:

Curious about what happens inside Nimbus Hatchery? Watch this 2019 video from PBS KVIE for an inside peek!

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