Inside Yellowstone National Park is a great green-blue lake, one that is much larger than the rest and mostly void of people. It’s pristine and wild, switching from calm and peaceful to thrashing and violent, from cold summer lake to frozen winter expanse.  

Its location in the world’s first national park is the foremost reason Yellowstone Lake has been preserved this way, a remnant of an undeveloped West. But just as the park has protected the lake, the lake has protected something too: Yellowstone cutthroat trout.

An estimated 42 species of wildlife, including grizzlies, ospreys and otters, have come to depend on the fish — a small but important resource.

The lake has long provided those fish a refuge. Its cutthroat populations have been robust, even as cutthroats around the country suffered from dams, overfishing and pollution. But even in its remoteness, Yellowstone Lake couldn’t protect the fish forever. In the 1990s, park officials began to realize it was no longer a cutthroat haven. The fish were at risk, and with them, an ecosystem.

It was likely more than a thousand years ago that cutthroat crossed the continental divide at Two Oceans Pass — a point where one creek splits into two and sends each half to different oceans. The cutthroat swam Atlantic Creek, which eventually flows into the Yellowstone River, which in turn flows through Yellowstone Lake.

There these cutthroat found a home, one that initially had no other fish to prey on them or compete with them for food. Over centuries, the trout became specifically tailored to live in the lake, and at one point it held as many as 4 million Yellowstone cutthroat. Wildlife came to depend on the fish, either as the vast majority or part of their diet.

Humans, too, would eventually find the good fishing.

Early park explorers like Gustavus Doane told great stories about the fisheries they found, as John Byorth, a historian and writer, described in his article, “Trout Shangri-La: remaking the fishing in Yellowstone National Park.”

In 1870, Doane wrote that the Yellowstone trout numbers were “perfectly fabulous” and noted that, with grasshoppers as bait, “the most awkward angler can fill a champagne basket in an hour or two.”

He and other explorers found “not only a wondrous place,” Byorth wrote, “but the kind of fishing paradise that prevents grown men from returning to their loved ones on time.”

As fishermen’s stories about the park spread, Yellowstone began to gain a reputation as an ultimate fishing destination. The reality, though, was that 40 percent of the park’s waters were devoid of fish, Byorth wrote.

To supplement the fishing, early park superintendents asked the U.S. Fish Commission to “see that all waters are stocked so that the pleasure seeker can enjoy fine fishing within a few rods of any hotel or camp.”

As part of that late 1800s effort, lake trout were introduced in the park’s Lewis Lake. The superintendents of that time couldn’t have known that in another century, the ancestors of those same trout would be putting the nearby Yellowstone Lake ecosystem at risk.

John Varley, a fisheries biologist and former chief of research for the park, sat in his office recently and recounted a day in 1993 that he remembers well. Now retired from the park and working as a Montana State University researcher, he still shakes his head when telling the story.  

He was giving a tour to Yellowstone’s new superintendent, Mike Finley, and telling him about issues the park was facing. Then Finley, a fisherman, asked Varley how Yellowstone Lake was faring.

“You’re in your mother’s arms,” Varley told him. “That baby’s on cruise control.”

Looking back, Varley sees how wrong he was. Just the next year, he and other biologists learned the devastating news that a lake trout had been caught in Yellowstone Lake — an introduction that would pose a serious threat to cutthroat.

In their book Yellowstone Fishes, Varley and Paul Schullery wrote, “nature didn’t do this. It was almost beyond question an intentional, illegal transplant.”

As Varley explained recently in his office, the discovery of lake trout was tragic to those who understood the value of Yellowstone Lake.

“That lake is as close to pristine as you get in the modern world,” Varley said. “As such it’s a jewel of extraordinary value.”

And suddenly, it was tarnished.

Not that lake trout are bad fish, they’re just in the wrong place — one known as a stronghold for Yellowstone cutthroat.

“Everybody who works in fisheries considers (Yellowstone Lake) to be the largest remaining concentration of Yellowstone cutthroat that exists throughout its range in the West,” said Todd Koel, a supervisory fisheries biologist for the park.

Varley remembers urging families to bring their children to the lake because it was one place where any kid could reel in a cutthroat.

“It used to be the greatest cutthroat lake in the world as far as fishing goes, and it isn’t anymore,” Varley now says matter-of-factly.

Since lake trout were discovered in Yellowstone Lake, cutthroat numbers have decreased by 75 percent. A large lake trout will eat an estimated 90 cutthroats each year, and because cutthroat evolved with no predators, they’re “just not genetically programmed to handle that,” Koel said. Lake trout also live longer, produce more eggs, and compete with cutthroat for food.

For years, biologists have measured cutthroat numbers at Clear Creek, one of their spawning grounds. In the 1980s, the decade before lake trout became a strong presence, the total run of spawning cutthroat there averaged 55,000.

In the past few years, that number has dropped to the hundreds.

As Varley put it: “There were 14 subspecies of cutthroat trout when white men trampled into the West, and now most of them are gone or barely hanging on. Yellowstone cutthroat were assured for most of the 20th century… Then they joined the rest on the dust heap of our natural heritage in the West, and that’s not right. It’s not right.”

But it’s not just the cutthroat Yellowstone Lake stands to lose. At stake are an estimated 42 species that, to some degree, depend on the lake’s cutthroat.

They include coyotes, bobcats, cougars, black bears, raccoons, grizzly bears, shrews, mice, squirrels, chipmunks, ermines, weasels, minks, martens, skunks, wolverines, badgers, white pelicans, mergansers, herons, gulls, grebes, loons, terns, cormorants, hawks, eagles, ospreys, kingfishers, jays, crows and ravens — an ecosystem of wildlife.

Lake trout cannot take the place of cutthroat, biologists say, because they are not adequate prey. They tend to live in deeper parts of the lake, as far as 60 to 70 feet below the surface. Birds can’t see them and scoop them up with their talons. Animals can’t often catch them from the shore. And lake trout spawn in the lake rather than creeks, where they would be vulnerable prey for bears and other animals.

If the cutthroat leave the lake, so will these birds and mammals. Already, grizzlies have abandoned the creeks where cutthroat spawning runs are now too few. Osprey nests are no longer common along the lakeshore.   

“Lake trout are affecting everything,” Varley said. “It’s changing away from how we’ve known it.”

But the park has a plan — one initiated in the 1990s that, revamped, may still be able to preserve the ecosystem.

When the lake trout were first discovered in Yellowstone Lake, the park called in a panel to evaluate what should be done. Its conclusion was the same as that of park biologists: there was no silver bullet to solve the problem.

So, the panel recommended a centuries-old technique: gillnetting. Since then, crews have been setting nets in the lake, reeling them in, and plucking out and killing the lake trout stuck in the mesh.

Basically, the goal of gillnetting has been to reduce lake trout numbers until their population is shrinking rather than growing. So far, the attempts have been like taking down an army’s front line, but the other hundreds of soldiers are still charging.

Not enough.

“Very naively, I thought that gillnetting would work with the program outlined,” Varley said. “I thought we would’ve broken the back of the lake trout population. That didn’t happen.”

In 2008, another panel was held. It advised park officials to double efforts by hiring commercial fisherman to help with netting. They did, and then four boats rather than two joined in the war against lake trout. Last summer, 150,000 of the fish were killed. Scientists can’t be sure how many lake trout there are in the lake, but they estimate there are hundreds of thousands.

This year, the park has again doubled efforts by hiring commercial fishermen for the full gillnetting season rather than half. By the end of the season, the crews hope to have killed a quarter million lake trout.

And this fall, what’s known as the “Judas” project might also begin. It would involve attaching trackers to lake trout to learn where their spawning grounds are. Then, netters could focus efforts there, killing fish before they lay their eggs. A panel that met in June made that project its number one recommendation, but it remains unclear whether the park will be able to fund it.

But will these ramped-up efforts be enough — or have park officials done too little, too late?

“I don’t know how any species could withstand this effort and make it,” Koel said. 
Varley, too, sounded optimistic.

“It’s still eminently doable,” he said. “I believe in the people who are in charge…They will follow through with this giant experiment.”

Still, Varley cautioned that eradicating or drastically reducing lake trout will take a sustained effort — and that means dedication to sustained funding. Currently, the work is one of the most expensive wildlife conservation projects in the park — at more than $1 million for this season. When so many fish are getting killed, it seems more worthwhile. But when the population finally starts declining and the netting still needs to continue, it’ll seem expensive to spend the money for just hundreds of fish killed each year, especially when there are many needs in other areas of the park.

“The last 20 will be million-dollar-a-piece fish,” Varley said. “That’s going to be a test of the agency’s resolve.”

Dan Wenk, the park superintendent, said the Yellowstone Lake project will continue to be a priority.

“Yellowstone cutthroat is an iconic species in its own right. It has defined the fishery of Yellowstone National Park as long as it’s been a national park,” he said. “It’s a species we must do all we can to restore to its prominence.”

He said he couldn’t guarantee that the project will always have an increased amount of funding each year or the same amount, but said it will be funded “to the level that we don’t lose ground and continue to gain ground.”

On a recent July day, Todd Koel navigated a skiff across Yellowstone Lake. Blue skies were overhead, and the only clouds hung near the still snow-capped peaks of the Absaroka range. Koel manages various fishery projects in the park, but he said this one forms the bulk of his work.

“There’s just so much riding on it,” he said.

This day he was heading out to check on the four gillnetting boats: the Kokanee, Sheepshead, Hammerhead and Freedom. Inside the latter, a net sat amassed on a long grey table, occasionally moving as fish jerked and writhed. Fisheries technicians Earl Drescher and Phil Doepke plucked fish out of the nets and, if they were lake trout, bopped them on the head and tossed them into nearby buckets.

“We’re saving the ecosystem,” Doepke said. “It’s like pulling dandelions in your yard.”

Sometimes cutthroat also get caught in the nets. At the end of the season, the average ratio of fish caught is 25 lake trout per one cutthroat. Of those cutthroat caught, about 25 percent live.

This day, only one cutthroat had been caught so far. A strong fishy smell filled the boat, and seagulls bobbed on the water nearby. Once the net had been cleaned and the fish buckets were full, the biologists planned to toss the lake trout overboard, where they would sink and settle at the lake bottom. That way, the fish’s nutrients stay in the lake system.

At another boat, the Hammerhead, workers told Koel they’d likely kill 800 to 900 lake trout by the end of the day. The number may seem small compared to the vast, unknown amounts that live in the lake, but each lake trout pulled from the deep, profound darkness is another chance for a cutthroat to live, and another chance to save a beloved ecosystem for future generations.

Eventually, Koel pulled his skiff away, back across Yellowstone Lake’s great expanse. Beneath the boat’s wake, cutthroat battle daily for survival against a growing population of lake trout. But in five years, Koel said things will begin to change, and Yellowstone cutthroat will start to regain their prominence.

“We finally need to get ahead and drive (the lake trout population) down into oblivion,” Koel said. “Enough is enough.”

Carly Flandro is a reporter for the Bozeman Daily Chronicle. She wrote this story for the Montana Quarterly.

Montana Quarterly

This article originally appeared in the fall edition of Montana Quarterly, which is available on newsstands. For subscription information, call 582-2676 or click here to visit the Quarterly's website.