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Fish-Killing Parasite Forces 180 Mile Closure Of Yellowstone River

Yellowstone River, MT
Wormwould (CC-BY-NC-2)
Montana Fish, Wildlife and Parks closed about 180 miles of the Yellowstone River downstream from Yellowstone National Park without a timeline for reopening. The closure could last months.

A microscopic parasite killing tens of thousands of fish forced state wildlife officials to close a portion of the Yellowstone River Friday morning.

Montana Fish, Wildlife and Parks closed about 180 miles of the Yellowstone River downstream from Yellowstone National Park without a timeline for reopening. The closure could last months.

"Our fish health specialists say this is unprecedented in Montana in terms of its magnitude."

Andrea Jones with FWP says in the past week officials have documented over 2,000 dead mountain whitefish, and have received reports of the kill beginning to affect some rainbow and Yellowstone cutthroat trout. No dead fish have been found inside Yellowstone National Park itself.

"Whitefish may be the canary in the coal mine. They tend to succumb or be more susceptible early to these kinds of parasites. We may begin to see larger numbers of trout, and we are doing our best in trying to limit the risk to other fish populations in the Yellowstone as well as reducing the chance of spreading parasite to other waters."

Jones says this disease has shown up in Montana twice in the past 20 years in isolated areas. But never to this extent.

The parasite causes kidney disease in fish. And the disease is made worse by stress factors:

"Environmental conditions primarily. The low stream flows, water temperatures but also, the recreational impact."

Jones says the peak daily temperature of the Yellowstone River since mid-July is hovering near 70 degrees. Ideally, for whitefish and trout, water temperature are in the mid 50s.

The closed section of river stretches from the Yellowstone National Park’s northern boundary at Gardiner downstream to Laurel.

Buddy Holcombe with the Flying Pig Adventure Company launched a fly fishing trip on the Yellowstone River around 6:30 Friday morning. A few hours later they were stopped by a FWP warden.

"He was really cool about it. We had already seen a few dead fish and kind of knew about the problem. But he just let me know that about a half an hour prior they had shut down the Yellowstone. They’re just trying to figure this thing out, I guess. I think a big thing with it is they’re worried about what kind of stuff people have on their boats. I image when I get back to town. I’m going to have to go to some kind of cleaning station."

Holcombe says there are other rivers he can take clients to, but he’s going to lose business.

"It's a pretty unique and special experience to float down the Yellowstone and catch fish. I’m not entirely sure how I’m going to handle that. I’ve got a lot of people to call and talk to. And people, this is their vacation, they’ve had these plane tickets and reservations booked for up to a year. And if somebody is getting on a plane today that’s coming on out here and fishing tomorrow, they’re just kind of SOL."

In Yellowstone and Park Counties, near the infected area, visitor spending totals nearly $200 million a year. And in Park County, just over a quarter of all jobs in the county are impacted by tourism.

Governor Steve Bullock says the state cannot afford for this disease to spread.

"A threat to the health of Montana’s fish populations is a threat to Montana’s entire outdoor economy and the tens of thousands of jobs it sustains."

Bullock says Montana’s outdoor recreation economy supports more than 64,000 jobs in Montana and generates nearly $6 billion a year in economic activity.

FWP’s Andrea Jones says nothing should go into the infected water.

"People should not be entering the Yellowstone, nor should dogs, etc. - anything that could move this parasite."

Upstream from the closed section of river, the National Park Service’s Charissa Reid in Yellowstone says that section of the river is still open.

"In the park we have a little bit of a different situation. We are at a higher elevation and the risk of us having that particular parasite is lower. We have not identified that parasite anywhere in the park and we haven’t had any dead fish reported inside Yellowstone."

In an aim to prevent the spread of the parasite officials are asking people to clean, drain and dry all of their equipment when moving between bodies of water.

FWP has two aquatic invasive species decontamination stations set up along I-90 near the affected areas.

Fishing guide Buddy Holcombe says his season of work is almost over, and although it could be a financial hit, he’s okay with having to leave the river early.

"You know it's whatever they got to do to maintain the longevity of this place. I think that is what people are worried about. Not necessarily losing a few days of work, but fishing is one of the things that makes this place great, and it is terrifying to have that put into jeopardy."

Recent outbreaks of this disease have been spotted in Washington, Oregon and Idaho.

Because of the environmental influences impacting the disease, the Yellowstone River could be closed for the rest of the season.

The parasite does not pose a health risk to humans.

Corin Cates-Carney manages MTPR’s daily and long-term news projects. After spending more than five years living and reporting across Western and Central Montana, he became news director in early 2020.
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