A native Yellowstone cutthroat trout is released after being caught last week on a fly in a tributary of Yellowstone Lake. Mail Tribune / Mark Freeman

Battle for Yellowstone Lake

YELLOWSTONE NATIONAL PARK — Mike Finley traveled earlier this month from his Medford home to his old stomping grounds to fish for one of America's more treasured trout in one of its most picturesque places.

Native cutthroat trout in the streams of Yellowstone National Park, where Finely was park superintendent for seven years, were more than willing to take turns biting Finley's barbless flies floated on creek surfaces.

"I'd catch maybe 10 and leave the hole for the next guy," Finley says. "I had 25-fish days. It's incredible."

Those cutthroats weren't there for Finley or that next guy a decade ago, instead fueling the massive cutthroat-eating machines of illegally introduced lake trout patrolling Yellowstone Lake for the past two decades.

Anglers like Finley can thank their lucky gillnets for the turnaround.

Nearly five years and $10 million into a massive effort to remove millions of invasive lake trout from Yellowstone Lake, the park's signature cutthroats are forging a comeback after literally being munched to the brink of extinction.

Intensive commercial gillnetting in the lake at the heart of this nearly 3,500-square-mile park has culled more than 1.4 million predatory lake trout. Yet biologists says they're only halfway toward hammering the lake trout population to a point where the population can be controlled long-term.

A key $5 million grant from the Yellowstone Park Foundation for trout-removal ends this fall, yet those striving to rebuild the cutthroat population hope to find funding from federal and private entities to continue doing to lake trout what the trout do to native cuts.

Groups such as Trout Unlimited are adding money and muscle to the effort to keep cutthroat, named for their tell-tale orange throat markings, among bison, grizzlies and wolves as apex fauna in America's signature national park.

"When it comes to native Yellowstone cutthroat trout, we won't make a five- or six-year commitment and say we're done when we're not done," park Superintendent Dan Wenk says. "This is the home to cutthroats. We have to deal with this fishery and we are."

The stakes are not just high for fly-fishermen, who help fuel a growing wave of visitors expected to hit 4.1 million this year.

Studies show spawning cutthroat missing from hundreds of miles of lake tributaries each fall, along with the resulting loss of progeny that rear in these streams, disrupt the natural food web involving 40 Yellowstone species ranging from grizzlies to otters and eagles.

"Lake trout suppression and native-fish protection is one of the top, if not the top, priorities," Wenk says. "Is there anything else more important? No. But there are other issues that are as important."

Biologists don't know exactly how lake trout ended up in Yellowstone Lake. The first was discovered by anglers July 30, 1994, and subsequent netting uncovered more. Tests showed the fish were from nearby Lewis Lake, where federal authorities first stocked lake trout for anglers in 1890.

Finley, who was superintendent in 1994, immediately launched netting programs to take on the lake trout and installed catch-and-release rules for cutthroats in hopes of stemming what seemed to him as the inevitable.

"I was distraught," Finley says. "I knew their capabilities. I knew how it would impact the ecosystem."

Cutthroat use the lake and its tributaries the way wild salmon use the ocean and coastal rivers. They feed in the lake then move as far as 40 miles up tributaries to spawn, and their progeny rear in those creeks before moving like smolts to the lake.

That creates a veritable buffet for adult lake trout, which quickly became so good at finding and eating cutthroat trout that full year-classes of young cuts began to all but disappear. Lake trout can live 30 years and are known to swallow fish two-thirds of their own body length.

"These fish are limited only by how far they can open their mouths," Park Service biologist Patricia Bigelow says.

Within a decade, the invasive trout whittled the cutthroat population down to 5 percent of its historic range, according to the Park Service.

"It's really good lake-trout habitat with no natural predators," Bigelow says. "We're trying to be that predator."

The Park Service and the coalition each pitched in $1 million a year for commercial fishermen to ply the lake for trout with 30 miles of gillnets set to target the invaders and avoid cutthroat. The effort has removed more than 300,000 lake trout annually the past four years and more than 200,000 so far this year.

"The idea is to get them into a death spiral," says Scott Christensen, the coalition's conservation director.

The big female lake trout can drop as many as 10,000 eggs when they spawn, Park Service biologist Todd Koel says.

"For every one that escapes us, that's the punishment she inflicts upon us in the fall," Koel says.

Once the lake trout population gets carved down by netting, biologists plan a regular assault on lake trout spawning grounds.

Thanks in part to more than $1 million in Trout Unlimited grants, biologists used radio-telemetry systems embedded in lake trout to find where they spawn in the fall. These so-called "Judas fish" led to the discovery of 12 specific shallow-gravel shoreline areas where lake trout are spawning.

The Park Service plans to use anything and everything from intense electro-shocking and suction dredging to cloaking the beds with the bodies of dead and decaying adult lake trout to render spawning areas as inhospitable as possible.

"It's all experimental now," Koel says. "The idea is to make those spawning beds really, really negative place for lake trout to be." 

But computer modeling shows it could take another five to seven years of aggressive netting to get to that point, Koel says.

While the fight against lake trout continues, the early results have proven promising to anglers like Finley, who hopes the assault on lake trout that started on his watch eventually will see native cutthroat swim free of their nonnative nemeses.

"I look at restoration projects as one of the most important things we do," Finley says.

Reach Mail Tribune reporter Mark Freeman at 541-776-4470 or Follow him on Twitter at

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