With extreme drought conditions reducing the cold water supply available, California Department of Fish and Wildlife (CDFW) are moving the last rainbow trout out of the American River Hatchery to avoid future losses of young fish to rising water temperatures. CDFW biologists predict that by mid-summer the temperature of the water entering the hatchery will exceed tolerable temperatures for the growing fish, causing extensive — if not total — loss of all fish in the hatcheries. The Fall Run Chinook salmon and steelhead from Nimbus Hatchery have all been released into State waterways.
“We are taking proactive actions to avoid catastrophic fish losses,” said Dr. William Cox, CDFW State Hatchery Program Manager. “It is an unavoidable change, and we need to look for unique opportunities to avert major losses. We will track all changes involved in the evacuation and evaluate how fish react to being released early. Ultimately we could develop new release strategies based on what we learn.”
American River Hatchery operations focus on taking rainbow trout eggs, while Nimbus Hatchery takes both salmon and steelhead eggs. Both hatcheries raise fish to release size. This will be the first time all stocks of fish at both hatcheries have been evacuated. By the end of this week all fish from both hatcheries will be released with nearly 430,000 fingerling steelhead from Nimbus Hatchery released into the American River, six months ahead of the normal February release time.
The remaining 20 state-managed hatcheries are expected to make it through the summer months and into the winter season without having to evacuate fish.
Normally CDFW would call on the Bureau of Reclamation to draft water from what is known as the “Deep Water Pool,” in the depths of Folsom Lake. The transfer of cold late water helps to keep hatchery waters acceptably cool. However, this year, the length and intensity of the drought is so extensive that little, if any water, in the lake is expected to be cool enough to utilize during sizzling summer months. CDFW predicts water temperatures will exceed 78 degrees in the hatcheries – far too warm for the young trout and salmon to survive.
Throughout the fall and winter CDFW workers mark hundreds of thousands of steelhead trout at Nimbus Hatchery. Unique markings will enable biologists to evaluate what happens to the fish throughout their life cycle and how the drought conditions will ultimately affect each type of fish.
Fall and winter rains, if received in sufficient amounts, will cool water temperatures enough to allow both hatcheries to come back online and resume operations.
Governor Brown has called on all Californians to reduce their water use by 20 percent and prevent water waste – visit SaveOurH2O.org to find out how everyone can do their part, and visit Drought.CA.Gov to learn more about how California is dealing with the effects of the drought.
Andrew Hughan, CDFW Communications, (916) 322-8944
William Cox, CDFW Fisheries Branch, (916) 358-2827