SACRAMENTO (AP) — Workers evacuated rainbow trout on Tuesday from a hatchery on the American River as part of rescue efforts prompted by concerns that California’s drought will increase water temperatures and kill the fish.

The state Department of Fish and Wildlife was using tanker trucks to remove trout from the American River Hatchery and have been taking fingerling steelhead from an adjacent hatchery, spokesman Andrew Hughan said.

The hatcheries are located about 20 miles east of Sacramento. The fish will be released at a much younger age and smaller size than usual.

The operation, which has been going on for several weeks, will continue on Wednesday. In total, about 2 million fish, including 430,000 fingerling steelhead, are being released months before they normally would.

“The set of circumstances dictated that we take this fairly drastic action,” Hughan said.

The evacuation is the latest effort to save fish during the dry conditions.

Millions of young Chinook salmon have been trucked to the ocean to spare them the dangers of migrating through depleted rivers and streams. In addition, state regulators have shut down recreational angling on portions of the American and Russian rivers due to concerns about salmon and steelhead trout.

The hatchery evacuations were prompted by concerns that water temperatures at the hatcheries could rise above 78 degrees because there’s so little mountain runoff. The temperature is considered lethal to the fish. The state’s remaining 19 hatcheries are expected to be OK.

“It just seemed like the right thing to do to get these fish out of the hatcheries and give them a chance and give the anglers a chance to have something,” said William Cox, the Department of Fish and Wildlife’s State Hatchery Program Manager.

State officials would normally call on the federal Bureau of Reclamation to tap a pool of cool water in Folsom Lake to reduce water temperatures at the two hatcheries. But they say the drought has been so severe that little, if any, water in the lake is expected to be cool enough.

The Department of Fish and Wildlife plans to monitor the released fish to see how they fare.

Cox said the smaller fish are definitely more vulnerable.

“The larger the fish are the better they do,” he said. “By releasing smaller fish, we know some will fall prey, they’ll not all survive.”