Montana Is Facing An ‘Emergency’ As ‘Zombie’ Trout Have Begun Appearing In Rivers Across The State

Published September 12, 2023
Updated September 13, 2023

The trout, blinded by infection and often covered in fungus, have begun appearing as native fish populations throughout Montana have declined.

Montana Zombie Fish Fungus

Big Hole River FoundationA diseased “zombie” trout discovered in Big Hole River in Montana.

The zombie apocalypse is in motion in Montana — and it’s waging a war against the trout population.

The Big Hole River is one of the top trout fishing regions in the world. But the trout population this year is at its lowest-ever recorded level. State biologists and guides say a disease making the fish resemble zombies is partially to blame.

“I have a video of [someone] netting a fish, could not see out of its left eye and was missing a chunk of its gil plate. I mean it looked like something out of The Last of Us,” said Wade Fellin in an interview with Montana Public Radio.

The Fellin family owns the Big Hole Lodge, which takes fly fishers out on the river. The family opened the lodge in the 1980s and has seen firsthand the effects of climate change in the region.

In addition to the dwindling numbers of the trout population, “we’ve seen whirling disease, red sores and lesions on fish, and brown trout with cauliflower fungus,” Fellin told the New York Times.

No one knows what specifically is causing these trout to become zombies. Montana Governor Greg Gianforte said tests on the affected trout have shown no unusual diseases or pathogens.

But experts and residents in the region aren’t satisfied with the state’s response to the crisis. They have called on Gianforte for years to create a task force on the threats to the region. Gianforte has thus far ignored their request, opting to delegate research responsibilities to state fisheries.

“We have an emergency in southwest Montana’s rivers, and we need to act immediately to avoid a total collapse of those trout fisheries,” wrote the nonprofit organization Save Wild Trout, formed by the Fellins and other local guides and researchers. “This is an all-hands-on-deck moment.”

When the Fellins opened the lodge in 1984, the river in the Beaverhead mountain range was clogged with ice until late spring. Back then, fly fishing season wouldn’t begin until June. Now, the river is often ice-free by April.

Big Hole River

Mike Cline/Wikimedia CommonsThe Big Hole River in January 2015. Experts say the river and surrounding ice used to melt into June. Now, they say, all the ice is gone by April.

Another effect of climate change in the region is the loss of key species, like the salmonfly, that make up a critical food source for the fish. A study on a Colorado river found that the salmonfly accounts for just over half of the trout’s diet.

Montana has warmed 2.7 degrees Fahrenheit since 1950. Temperatures in the high Rocky Mountain range are increasing at least twice as fast as the rest of the nation. Cold winters and springs are crucial to the Big Hole River to provide the fish with the cold, clear water they need to thrive.

“There is an ongoing aridification of the West,” said Steven W. Running, a professor emeritus of ecosystem and conservation sciences at the University of Montana. “As it warms up, evaporation increases and precipitation is not increasing, the snow melts earlier. Once you’ve melted through that snowpack, there is nothing to cool that water down” as it travels to the rivers.

Warmer water also has lower levels of dissolved oxygen, which has a huge negative impact on the fish.

The Save Wild Trout plans to gather experts to study the declining trout population, identify causes, and propose solutions. As of June, Brian Wheeler, director of the Big Hole River Foundation, is the only person collecting data in the region.

After reading about the bizarre “zombie” trout in Montana’s rivers, learn about another fish that looks like it came from a horror movie: the mysterious football fish. Then learn about the strange and ethereal barreleye fish that hunts in the shadows of the deep sea.

Hannah Reilly Holtz
Hannah Reilly is an editorial fellow with All That's Interesting. She holds a B.A. in journalism from Texas Tech University and was named a Texas Press Association Scholar. Previously, she has worked for KCBD NewsChannel 11 and at Texas Tech University as a multimedia specialist.
Matt Crabtree
Matt Crabtree is an assistant editor at All That's Interesting. A writer and editor based in Salt Lake City, Utah, Matt has a Bachelor's degree in journalism from Utah State University and a passion for idiosyncratic news and stories that offer unique perspectives on the world, film, politics, and more.
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Holtz, Hannah. "Montana Is Facing An ‘Emergency’ As ‘Zombie’ Trout Have Begun Appearing In Rivers Across The State.", September 12, 2023, Accessed June 14, 2024.