Rainbow trout and steelhead are being evacuated from two hatcheries on the American River amid concern California's drought will cause the water to become warm enough to kill the fish.
The Sacramento Bee reports the state Department of Fish and Wildlife will use tanker trucks on Tuesday to remove about a million trout from the American River Hatchery.
The fish will be planted in lakes throughout the state as usual, but at a much younger age and smaller size.
The department will also release 430,000 Central Valley steelhead from Nimbus Hatchery into the American River - about six months earlier than usual.
Water temperatures of 78 degrees are considered lethal to the fish.
Officials say temperatures in the American River could become that warm later this summer because there's so little mountain runoff.