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March 8, 2017 – Nearly a half million young steelhead recently started their journey to the ocean thanks to the California Department of Fish and Wildlife (CDFW). Staff at Nimbus Fish Hatchery nursed the young steelhead through several potentially devastating conditions, including drought-induced high water temperatures in the hatchery last summer and winter flood conditions that nearly cut off usable water supplies and carried dangerous levels of silt into the hatchery’s normally clean water distribution system.
“The fish we released will be returning to the American River over the next two to four years, and we are proud and relieved to have brought them this far,” said Gary Novak, the Nimbus Hatchery manager. “Steelhead are hardy, but considering their size and the number of environmental obstacles cropping up in rapid succession, they still needed human intervention in the hatchery to ensure a better chance of survival in the wild.”
All 420,000 young steelhead were released into the American River just upstream of the I Street Bridge in Sacramento. Due to the high water conditions, the juvenile fish are expected to make excellent time traveling down the Sacramento River to the Bay and eventually on to the Pacific Ocean. Losses to predators are believed to be lower during turbid water and high flow conditions.
During January and February 2017, water releases from Nimbus Dam reached 80,000 cubic feet per second (cfs), which is well above the normal 6,000 to 10,000 cfs. The high flows created conditions that dislodged exceptional amounts of debris, clogging the intake structure at Nimbus Fish Hatchery and creating near-lethal levels of nitrogen in the water. Hatchery staff worked around the clock over a month-long period to keep the water intake open, clear water distribution points, tanks and raceways of silt, and install aerators to lower nitrogen levels.
Fish health assessments by CDFW pathologists found the steelhead to be in satisfactory condition and near the average weight for fish their age prior to release. It remains to be seen how the stressors of living in turbid water and enduring some periods of high nitrogen levels will affect the fish. Annual returns of mature steelhead to Nimbus Hatchery have varied widely in recent years, from a high of 3,409 in 2013 to a low of just 150 the following year.
All the fish in this release were marked with an adipose fin clip.