Rainbow trout and steelhead are being evacuated from the American River and Nimbus fish hatcheries amid drought concerns.
The state Department of Fish and Wildlife says low amounts of mountain runoff could lead to a rise in water temperatures that would be lethal.
So, about a million trout will be planted in lakes at a much younger age and smaller size than usual.
More than 400,000 Central Valley steelhead will also be moved into the American River.
So far, only the two local hatcheries have been affected, and the 20 other state-run hatcheries will be able to make it to the winter without having to evacuate.