The number of steelhead showing now at Nimbus Fish Hatchery on the American River continues to be much better than last year, in spite of continuing low releases of 500 cfs from Nimbus Dam. If the El Niño storms continue, expect to see a lot more steelhead move into the river when the flows go up.
Last season hatchery workers counted only 154 steelhead trapped at the facility from December through mid-March.
In contrast, the hatchery has trapped a total of 320 adult steelhead to date. ‘”We also released two wild girls and one wild boy,” said Gary Novak, Nimbus Fish Hatchery manager.
“There are lots of steelhead in the hatchery now. We’re seeing about 80 fish in the trap every Tuesday before we spawn,” stated Novak.
The hatchery has spawned 73 pairs and taken 491,717 eggs, well on the way to their goal of releasing 430,000 steelhead yearlings into the river system.
However, to put the current steelhead run in perspective, banner years for steelhead on the American have seen up to 2,000 adult steelhead counted by this time of year. During the best seasons I’ve fished for steelhead – 1980, 1995, 1999, 2002, 2003, 2004, 2011 and 2013 – anywhere from 2,000 to 4,000 steelhead have been counted at the hatchery.
Novak’s working theory for the much larger numbers of steelhead seen this year is that many of the fish didn’t come back to the river and stayed out in the ocean for an extra year. Most of the fish seen at Nimbus are three-year olds in the majority of years.
This year there appear a larger number of four-year-olds than usual, but we won’t know for sure until the scale samples of the fish are analyzed. Most of the fish this season range from 8 to 12 pounds.
The hatchery workers continue to see larger amounts of eggs per steelhead female, 7,000 compared to around 6,000 eggs per fish last year.
The hatchery last year was able to take only 192,278 eggs the entire season. To boost the numbers of fish they raised, they obtained 168,838 eggs from Coleman Fish Hatchery, Novak noted.
This year CDFW staff will release 291,000 steelhead yearlings into the system.
American River steelhead are the largest ones found in the Central Valley system, due to their Eel River ancestry and excellent forage conditions found on the river. A fisherman tossing out a Little Cleo in February 2002 caught and released a wild steelhead/rainbow weighing 24.02 pounds, the largest ever documented on the American.
After just hundreds of the river’s native steelhead returned to Nimbus Fish Hatchery in the first few years after Folsom Lake was completed in the 1950s, the DFW introduced Eel River steelhead to the hatchery, boosting annual steelhead returns to the hatchery in the thousands every year.
Genetic analyses conducted since then indicate steelhead from both the hatchery and the river are genetically more similar to Eel River steelhead than other Central Valley steelhead stocks.
In a presentation before the Save the American River Association in December 2014, Dr. Ribert Titus, CDFW Senior Environmental Scientist, documented how steelhead in the lower American River 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 steelhead encounter every summer have spurred the outbreak, first documented in 2004, of an anal vent disease called “rosy anus” according to Titus.
The American River steelhead population, along with its Chinook salmon run, constitutes a unique urban fishery in the shadow of the State Capitol that we must fight to restore and preserve.