Yellowstone River Whitefish Die-Off

A microscopic parasite is destroying the fish population of the Yellowstone River, causing Montana Fish, Wildlife and Parks (FWP) to take the extraordinary step of closing a 183-mile stretch of the Yellowstone and its tributaries to all water-based recreation (fishing, wading, floating, tubing, boating). The closure affects the river from Gardiner, at the north end of Yellowstone Park, to Laurel, and includes major tributaries.












In the past 2 weeks, FWP has discovered over 2,000 dead Mountain Whitefish along this stretch of river, and expects that the total kill will climb to the “tens of thousands.” According to FWP, the kill is beginning to impact some Rainbow and Yellowstone Cutthroat Trout.

The parasite is tetracapsuloides bryosalmonaewhich causes proliferative kidney disease (PKD) in salmonids, one of the most serious diseases that can impact whitefish and trout. According to FWP, the disease can be 20-100% fatal in trout. Unfortunately, more scientific estimates are not available as the disease has not been widely present, and therefore rarely studied, in the Northern Rockies.

Read more about the PKD parasite on Montana FWP’s website, click here.

The closure will have a dramatic impact on Montana’s outdoor recreation economy, which is responsible for more than 64,000 jobs and nearly $6 billion in yearly economic activity. In stressing the urgency of the situation, Governor Bullock stated, “We must be guided by science. Our state cannot afford this infectious disease to spread to other streams and rivers and it’s my responsibility to do everything we can to stop this threat in its tracks and protect Montana jobs and livelihoods.”

FWP will continue to monitor the river and will lift the closure when stream conditions such as flow and temperature improve and fish mortality ceases. Unfortunately, this means we could be waiting until mid or late September for the river to open, given the typical growing season and water use patterns in Paradise Valley.

What Does the Yellowstone Whitefish Die-Off Mean for Montana’s Other Rivers?

The PKD parasite is native to the northern US, Canada and Europe, but outbreaks have not been common. According to FWP, there have been only two isolated PKD outbreaks in Montana in the last 20 years, and local reporters found records of a huge die-off in the Upper Snake about a decade past.

Why such a huge die-off, and why now?

According to the FWP report, the effect of the disease on Yellowstone’s fish populations is exacerbated by other stressors like near-record low flows, consistent high temperatures, and the disturbance caused by recreational activities. We also know that these stressors, here in Montana, are extreme:

  • The area of the Yellowstone River system that has suffered the PKD outbreak is suffering from extreme drought conditions. According to the Montana Department of Natural Resources and Water Conservation, Sweetgrass, Stillwater, and Yellowstone counties — the primary locations of the closure — are all suffering from extreme drought as of July, 2016.

  •  2014 and 2015 were the hottest years in recorded global history, and 2016 will set a new record. In fact, we have had over 30 consecutive months of record temperatures. These temperature increases have been felt in Montana. According to the federal government, average spring temperatures in the state have risen by almost 4°F over the last 55 years; summer temperatures have risen by over 1°F during the same period.

  • Drought and increased temperatures reduce river water flows. We see this floating our local stretches of the Gallatin, Madison, and Jefferson, and by looking at this years’ USGS stream flow gauges.

We must accept the scientific fact that these conditions are no longer temporary.  Indeed, droughts, warmer temperatures, and lower river flows have been consistently occurring in Montana for some years now, and are most certainly part of our future.

According to the article “Life cycle complexity, environmental change and the emerging status of salmonid proliferative kidney disease,” published in the journal Freshwater Biology in June, 2010:

“Environmental change is likely to cause PKD outbreaks in more northerly regions as warmer temperatures promote disease development, enhance bryozoan biomass and increase spore production, but may also reduce the geographical range of this unique multihost-parasite system. Coevolutionary dynamics resulting from host–parasite interactions that maximise fitness in previous environments may pose problems for sustainability, particularly in view of extensive declines in salmonid populations and degradation of many freshwater habitats.”

Some in Montana will say that this is an unfortunate chance outbreak of this disease.  The truth, rather, is that this isn’t chance. The Yellowstone’s die-off is what climate change looks like. It means that, as the conditions that encourage diseases like PKD become more prevalent, so will future outbreaks of these and other diseases.

Upper Missouri Waterkeeper sees the Yellowstone die-off as a pressing reminder that we must be vigilant in working to improve water resources management in SW Montana’s Upper Missouri River Basin.

This means, practically speaking, that we must use all the tools on our tool-belt to stop existing sources of pollution to our rivers while, on the other hand, working together to change broken aspects of our water management system which are now part of the problem, not the solution.  The consequences of inaction are plain: death by a thousand cuts, starting with the decline of our rivers.


*This article is taken from the writings of Montanan David Katz, author of Preserve the Beartooth Front. We thank David for his clear articulation of a complex issue and unswerving dedication to finding meaningful solutions to challenges confronting management of Montana’s natural resources.*