Researchers say no sign in 2 years of proliferate kidney disease that ravaged Yellowstone River
Nate Howard — Enterprise Staff Writer
Wednesday, September 18, 2019
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Enterprise photo by Nate Howard

Patrick Hutchins, a biologist with the U.S. Geological Survey, collects a water sample from the Yellowstone River. In the background are two cages stocked with rainbow trout for the scientist’s research.

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Enterprise photo by Nate Howard

Hatchery-raised trout are taken from a cage in the Yellowstone River and placed in a bag before being studied for PKD.

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Enterprise photo by Nate Howard

Scott Opitz, a biologist with the Montana Department of Fish, Wildlife and Parks, is photographed along the bank of the Yellowstone River at Mayor’s Landing Fishing Access.

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Map courtesy of Montana Department of Fish, Wildlife and Parks

This map shows the PKD mortality monitoring sections of the Yellowstone River in 2018. 

On a late summer day, Patrick Hutchins drives south on East River Road, going from one fishing access to the next along the Yellowstone River collecting hatchery rainbow trout from cages.

Beyond Hutchins, granite mountain peaks rise, holding what has long made the Yellowstone prime trout habitat. Each spring, the snowmelt comes rushing down the steep mountains, creating the critical element of the trout’s survival — cold, clean water.

Hutchins, a molecular biologist with the U.S. Geological Survey, and his team planted two fish cages at four sites on the Upper Yellowstone — between the Grey Owl and Mallard’s Rest fishing access sites in Paradise Valley, which was the “kill zone” hotspot of fish mortalities during the 2016 outbreak of proliferative kidney disease that killed tens of thousands of fish.

Hutchins is trying to answer the question: Why was there a fish kill on the Yellowstone in 2016 when nearly identical conditions were present on other rivers?

And he’s hoping that those caged trout might have the answer. One thing they do know: For two years, no cases of PKD have been found in the trout placed in the Yellowstone. But questions about the devastating disease remain.


Each week, Hutchins and his team remove 20 rainbow trout from each of the eight cages that hold 40 hatchery-raised rainbow trout apiece.

They then freeze the fish before dissecting them and taking DNA samples for a bryozoan called Tetracapsuloides bryosalmonae, or “Tbryo,” the native parasite that causes proliferative kidney disease in fish.

The team is comparing the Yellowstone to five other rivers: the Madison, Ruby, Big Hole, Jefferson and the South Fork of the Snake River in Idaho, where a fish kill caused by PKD occurred in 2012.

“There’s very little data on the Yellowstone,” said Hutchins.

Hutchins is trying to change that. His team samples the water flow, makes observations and collects “e-DNA,” or environmental DNA, and samples from soil, water and air.

Stream flow and temperature readings have been collected for decades, but those numbers do not give biologists the full picture of what’s actually living in the river.

“If I had trout kidneys from 50 years ago, I could solve a lot of questions,” said Hutchins.

Perfect storm

The Yellowstone River is the longest free-flowing river in the United States. It’s clear, cold waters make for a blue ribbon trout fishery that brings anglers from across the world who spend $70 million a year in Park County.

In August 2016, a “perfect storm” struck the river, said Scott Opitz, a biologist with the Montana Department of Fish, Wildlife and Parks. The warmest waters ever recorded in the Yellowstone and decreased flows led to an outbreak of Tbryo, resulting in the unprecedented closure of 183 miles of river from Gardiner to Laurel by FWP.

Opitz said the groundwork for the fish kill was laid in the spring of 2015 with extremely low water levels and warm temperatures. In 2016, warmer spring temperatures brought rain instead of snow, leading to decreased flows. Snowpack is a slow, steady cold water release, while rain causes an immediate rise in water levels but adds no late-season water, explained Opitz.

The fish kill affected mostly mountain whitefish.

Mountain whitefish, which historically have been paid less attention than the popular sport fish species of trout, are an indicator species of river health — a canary in the coal mine, Opitz said.

So when whitefish started turning belly-up in the Yellowstone, something was clearly wrong. They’re more sensitive than nonnative trout species such as brown, brook and rainbows, which died in much fewer numbers Opitz said.


This past spring, FWP continued sampling fish populations at Mallard’s Rest Fishing Access, and Opitz was pleased to find that after two years of trout decline, primarily in large, older trout or members of the salmonid family, these fish populations are on the rise again.

“Each year we’re seeing more and larger fish, especially brown trout,” Opitz said.

Looking back, the fish kill of 2016 was likely a double whammy on the fish.

Optiz said warmer water and low flow increases the stress on fish, weakening their immune systems.

It also creates crowding of fish and the parasite in less habitat, creating a higher chance for the fish to be in contact with the parasite.

As scientists investigated the cause of PKD, FWP and USGS personnel visited the water treatment plant in Gardiner.

They also looked at the water draw from the Yellowstone and its tributaries for agriculture.

But in all the studies, “they certainly don’t appear to be a source,” Opitz said.

With many questions still unanswered, all scientists like Opitz and Hutchins can do is build a base of information that can be used if another outbreak occurs.


Fishing industry on the rise after fish kill

By Justin Post — Enterprise Staff Writer

John Bailey still gets calls from anglers — from all over the world — asking if they travel to the area will they will be able to fish the blue-ribbon Yellowstone River.

The calls are a new thing. Ever since the massive mountain whitefish die-off of 2016, many anglers are more cautious when booking a river trip on the Yellowstone River, says Bailey.

“I think it’s still hurting,” he said. “We get calls — you would be surprised how many — ‘If we come will we be able to fish?’ When there’s doubt, people don’t do things.”

Bailey and others working in the area’s fly-fishing industry say conditions — primarily water temperatures — on the Yellowstone River have improved in the two years since the die-off, but the 2016 event still lingers in the minds of anglers from the area and beyond.

And it’s understandable why some anglers may pause during their preparations to visit the Yellowstone from far-flung areas.

The 2016 die-off led to the unprecedented closure of the Yellowstone River, stretching from Aug. 19 to Sept. 2, 2016 and with some sections shut down even longer.

Fishing guides were out of work. Fly shops lost business. Hotels and restaurants were also impacted by the closure. The University of Montana Institute for Tourism and Recreation Research estimated in 2017 that the 17-day closure had a negative impact on Park County to the tune of $676,000, The Livingston Enterprise reported in December 2017.

Today, Bailey said his phone rings a little less than it did in the immediate year or two after the closure, but people still call inquiring about the river in the wake of proliferative kidney disease, or PKD, which caused the 2016 die-off.

“August made me feel much better,” Bailey said, adding that river temperatures remained cool throughout the summer this year. “There were many more people here in August.”

For Bailey, the question all Montanans should be asking moving forward is how all river users, and not just sportsmen, will contribute financially to the future health of the river and fishing access sites.

“I just think everybody using it should participate in some form,” he said, adding that the growth of the region should be part of the larger discussion.

“The story is — what’s Bozeman going to do to everything?” Bailey said.

Bailey said sportsmen have long contributed to funding the Montana Department of Fish, Wildlife and Parks while recreational floaters and others don’t pay to enjoy the resource.

“All these other people have it for free,” he said. “I think that needs to change.”

Adam Wagner, a former science teacher and current owner of Sweetcast Angler in Big Timber, said the health and environmental conditions on the Yellowstone River weigh on his mind as each new summer season approaches.

While cool river temperatures with highs in the 60s have been the norm the last two years, Wagner said he’s concerned that another year with low streamflows and high river temperatures, such as in 2016, could return in the future.

“We’re kind of prisoners of Mother Nature in this situation because if we get a good winter with lots of snow I think we’re in good shape,” Wagner said. When I start worrying is when we don’t have snow in the wintertime. You never know what’s going to happen, especially after 2016.”

Wagner said his shop took a hit after the 2016 river closure, yet this summer he was pleased to witness a return of anglers to the region during the traditionally warm weeks of August.

“I think it took a little while to get some of that fall business back, but after a couple years we’re back to normal as far as guide trips and fishermen,” he said. “I think the fish are real healthy and the river’s healthy.” 

Dan Gigone, owner of Sweetwater Fly Shop in Livingston, said that in the years since the 2016 fish kill, he’s noticed more anglers seeking to fish in September and October rather than August.

Gigone said September and October are good bets for fishing the Yellowstone, as there is less pressure and river temperatures are cooler.

However, Gigone doesn’t think anglers have seen the last of PKD and its impacts on the Yellowstone River, especially if warm August temperatures return in the coming years.

“Climate change is the gorilla in the room and I do think, as climate change accelerates and continues, that we’ll have some rough times,” he said. “We’ll be lucky if we have a cold-water fishery, but if not, we’ll fish for smallmouth bass.”