Yellowstone Trout: Scientists Kill Off Millions Of Invasive Lake Trout

A Yellowstone trout invasion appears to be waning after scientists spent decades fighting off a non-native species of fish that took over lakes and pushed out native fish.

Someone illegally introduced non-native lake trout into Yellowstone Lake in 1994, and the fish spread quickly across the 132-square-mile body of water. Since that time crews have taken on great efforts to capture and kill the fish, which can grow to several feet long and weigh as much as 30 pounds.

Government scientists now say the Yellowstone lake trout are on the decline, but a debate has been forming over whether the efforts are worth the $2 million annual cost. In many places across the United States, lake trout are prized as a sport fish.

But backers say the invasive Yellowstone trout have been cutting into the population of cutthroat trout, one of the most important native species in the first national park in the United States. A number of animals including grizzly bears, bald eagles, and osprey feed on the cutthroat trout.

The native cutthroat trout also propped up a $30 million recreational fishing industry in Yellowstone Park.

Each year biologists have netted and killed close to 300,000 Yellowstone lake trout, but they say the fish have been harder to catch in the past few years. They take that as a sign that the efforts are working.

“The goal was to crash the lake-trout population to a point where they are no longer adversely affecting Yellowstone cutthroat trout,” said Dave Hallac, chief of Yellowstone’s Center for Resources. “We have evidence now that our suppression program is sufficient to cause the population to decline.”

There also appears to be an increase in the numbers of young cutthroat trout, scientists say, giving them optimism for the future.

“I’m very encouraged by some of our recent successes,” Hallac said. “The goal is to crash the population of lake trout to a point where they are no longer adversely impacting Yellowstone cutthroat trout.”

Biologists say they still have more work to do to eliminate the invasive Yellowstone trout, but believe they’re going in the right direction.