Fears of potentially deadly water temperatures have forced California officials to evacuate fish from two hatcheries into state waterways, in the hopes of avoiding “catastrophic” fish losses.
California’s extreme drought and high temperatures have led to fears that, by the middle of the summer, water temperatures would be too high in hatcheries for young fish to survive. Too-warm water could cause “extensive — if not total — loss of all fish in the hatcheries,” California officials said, so over the past several weeks two of the state’s hatcheries have been releasing rainbow trout and steelhead from two state hatcheries into rivers and lakes. This is the first time these hatcheries have been forced to completely empty out their stocks, said William Cox, California’s Department of Fish and Wildlife’s State Hatchery Program Manager.
“We are taking proactive actions to avoid catastrophic fish losses,” Cox said in a release. “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.”
Usually, steelhead are raised in hatcheries until they’re about a year old, at which time they’re released into the American River where they make their way to the ocean. This year, the steelhead are being released into the river at about 6 months old, making them ill-prepared for life in the river, Cox told ThinkProgress. When steelheads reach a year old, they’re physiologically and instinctively prepared to travel to the ocean — at six months, they don’t have that drive to swim out to the ocean, so they’ll try to make it in the river. But high water temperatures, low water flow, and clearer-than-normal river water that makes the young fish easier for predators to spot all make it unlikely that these fish will survive.
The young rainbow trout — some of which are only about two to four inches long — are being sent to lakes, where they have a better chance of survival than the steelhead do in the river.
CREDIT: U.S. Drought Monitor
Peter Moyle, professor and associate director of the Center for Watershed Sciences at the University of California, Davis, said he expects a very low survival rate for the fish, especially for the steelhead.
“These fish are very unlikely to make it,” Moyle said of the steelhead. “They’re releasing 450,000 fish all at once into a river which is full of other fish, including other predators. These fish are hatchery fish — they’ve never experienced anything but life in a cement trough — so they are ill-equipped for surviving in the wild.”
Cox said he thought the evacuation of the steelhead likely wouldn’t have an impact on local economies, but releasing the rainbow trout all at once into lakes may have an impact on towns that rely on fishermen to visit throughout the summer to fish. Since the fish are all being released into these lakes at once, the fishermen may come all at once and then stop coming later in the summer.
In non-drought years, when water temperatures look like they’re going to get too high (78°F can be lethal to fish), California’s hatcheries can request that the Bureau of Reclamation pull cold water from the depths of Foltsom Lake for the hatcheries to use. The addition of cool water helps bring the overall temperature of the hatcheries’ water down, but this year, the extensive drought means that there isn’t enough cold water at the bottom of Foltsom Lake to use. Cox said there aren’t any other practical ways to cool the hatchery water — large water chiller would work, but they’re expensive to buy and use, due to their high energy demand. But, he said the Department of Fish and Wildlife is considering buying some small-scale coolers or investing in other measures to cool water in local streams to help wild fish survive.
California’s extreme drought has put major pressure on the state’s fisheries this year. Low flows and high temperatures in the state’s rivers have forced officials to truck about 50 percent more young hatchery-raised salmon out to sea than usual. And wild fish aren’t faring well either — low stream levels are making migration difficult for the state’s endangered Coho Salmon, leading to fears of extinction for the species. Moyle said more won’t be known about the Coho’s status until late summer, when it’s more clear how the state’s water has been allocated.