Bear food

Yellowstone cutthroat trout provide a food source for animals like grizzly bears and ospreys. The fish's decline has forced such species to look elsewhere for a meal.

Yellowstone National Park officials say they’re making a significant dent in the lake trout population in Yellowstone Lake, clearing space for the park’s native cutthroat trout.

Yellowstone and contract crews culled 282,960 fish this year, according to a park news release.

The total is smaller than last year and the year before that, signaling a decline in the overall number of lake trout. That’s good news for Yellowstone cutthroat trout, which suffered a major decline after the detection of the nonnative 25 years ago.

But the fight against lake trout isn’t over. A panel of experts told the park in May that it would need at least another five years of suppression work to hit its goal of a population under 100,000.

“There is a considerable amount of work yet to do to build on this progress,” Yellowstone Superintendent Cam Sholly said in the release. “This will continue to be one of our conservation priorities.”

Lake trout were first detected in Yellowstone Lake in 1994. The population grew across the waterbody in the southern part of the park and started taking bites out of the cutthroat population. The release said Yellowstone cutthroat are “the park’s most ecologically important fish and the most highly regarded by visiting anglers.”

Work to kill lake trout began the same year the species was detected. The release said Yellowstone has spent more than $20 million on recovering cutthroat there over the past 20 years.

So far, more than 3.4 million fish have been removed, according to the park.

This year’s lake trout catch is 29% lower than the total from 2017, when more than 396,000 fish were netted. Crews are also finding a decline in the number of fish per net — coming in at 2.9 this year compared to 4.4 in 2017.

Population models suggest there are 73% fewer lake trout 6 years old and older in the lake now than at the population’s peak in 2011, according to the release.

The park is also working on new ways to hobble lake trout growth, like suffocating their eggs and preventing reproduction. The technique is producing promising results so far, according to the release, and the park may expand it in the future.

As they’re seeing the decline in lake trout, park biologists are also finding more and more cutthroat. Fisheries staffers found a lot of cutthroat in the Thorofare region this past July — something they wouldn’t have found 10 years ago, according to the release.

Todd Koel, who leads Yellowstone’s Native Fish Conservation Program, said in the release that there are a lot of benefits from all this work.

“The park will never completely eradicate lake trout, but the return on investment is the ecological restoration of Yellowstone cutthroat trout, sustainable angling, and a chance to glimpse a river otter, osprey or bear catching a cutthroat,” Koel said.

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