JACKSON, Wyo. – An extensive effort to capture and kill non-native lake trout in Yellowstone Lake is showing progress with fewer of the invasive fish being found.
“In 2018 so far, we’ve caught basically 155,000 lake trout, and that’s 63,000 less than this time last year,” Yellowstone National Park fisheries chief Todd Koel told the Jackson Hole News & Guide. “That’s huge. It’s a real signal that this population is finally crashing. It’s what our science has predicted and the population modeling has predicted, and now we’ve finally started seeing it on the ground, which is great.”
The effort against the lake trout is the centerpiece of a long-term fight to help Yellowstone’s native cutthroat trout. Lake trout feed on cutthroats, causing the native fish population to decline.
The decline in lake trout is showing up in the size of the fish being caught, Koel said.
“There have been less and less large lake trout out there for many, many years,” he told the newspaper. “Now we’re seeing declines in the smaller fish.”
The lack of 2- and 3-year-old lake trout showing up in gill nets suggests that the slaying of larger lake trout slowed down reproduction several years ago.
The National Park Service had been predicting the crash of Yellowstone’s lake trout population for several years. Entirely eliminating lake trout in the 136-square-mile (352-square-kilometer) lake is believed to be impossible, and so the suppression efforts, in some form, will likely continue in perpetuity.
A 2015 Montana State University dissertation predicted that it would take another 14 years of intensive lake trout killing to rebound native cutthroat trout to conservation goals sought by managers.
“We have no intention of letting off on the netting pressure at all,” Koel said. “In fact, we’ve been talking about increasing it more. We want to put the nail in the coffin of these lake trout.”
Yellowstone’s netting program costs about $2 million a year.
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