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Trout disease in hatcheries leads to lack of the fish in area lakes

It’s summertime and the fish aren’t jumping. At least not the trout in Southern California.

A contagious, potentially fatal bacteria has infected trout in the three state-run hatcheries that provide the fish to public lakes in Southern California and the eastern Sierra. The California Department of Fish and Wildlife expects to euthanize all 3.2 million trout in those hatcheries this week.

The disease, which never before has seen in California, was first identified at the Mojave River Hatchery in Victorville in April, and then at the Black Rock and Fish Springs hatcheries in the Owens Valley in June.

Quarantines were immediately put in place but biologists have been unable to eliminate the illness, known as Lactococcus garviae.

“This bacterium is resistant to all the treatment options we have available for fish,” said Jay Rowan, program manager for the Department of Fish and Wildlife hatcheries. “The fish losses were getting worse despite our treatments. The best option we have available that will get us back to planting fish from these hatcheries in the shortest timeline … is to start over.”

While some trout will be diverted to Southern California lakes from hatcheries elsewhere in the state, it takes two years for a trout to grow to a catchable size and Rowan estimated it will be 2022 before trout stock in the area’s lakes returns to usual levels.

“There’s no way to make up for those fish,” he said. “It’s going to take time to get back to where we were.”

So far, the bacteria has not been found in fish already in lakes. But Rowan said it may just be a matter of time before fish there begin showing symptoms of bulging eyes, lethargic swimming and premature death, as trout were planted in lakes before the disease was identified.

“It’s probably likely we released infected fish,” he said. “If there are sick fish and fish are dying, we’ll hear about it pretty quickly from anglers and from Fish and Wildlife biologists.”

For anglers eager to hook trout, Rowan recommended keeping an eye on the fish planting schedule on his department’s website and noted that trout tend to get fished out quickly. As of Tuesday, July 28, the only fish stocking scheduled in the greater Los Angeles area was at Big Bear Lake, where the planting is listed as ongoing this week through Saturday, Aug. 1.

Other fish, including bass and blue gill, are at their normal levels in most lakes. Privately stocked lakes with trout may also be at normal levels.

Human infection?

It’s unknown how the bacteria made its way to California, but it’s been found in bird feces and Rowan said one theory is that birds brought it to the state.

The disease has recently been identified in Washington and the Midwest in recent years. Historically, it “has been reported in cattle and poultry farms as well as fresh and salt water fish and shell fish hatcheries around the world,” according to the Department of Fish and Wildlife website.

“Fish-to-human transmission of this bacteria is rare and unlikely but there are several documented instances associated with immuno-compromised people consuming infected raw fish and unpasteurized milk products,” according to the website.

It’s uncertain how the department would respond if the bacteria begins showing up in fish already in lakes.

“There are so many variables to a situation like that that I can’t say with a lot of certainty what our response would be,” Rowan said. “How we respond would depend a lot on how wide spread in the environment it was, if fish in the water or waters were exhibiting symptoms or if they were just asymptotic carriers, etc.”

In the meantime, the diseased hatchery fish will be euthanized by injecting CO2 into the water.

“It’s painless,” Rowan said. “They just fall asleep.”

Source: Orange County Register

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