Hundreds of dead mountain whitefish have washed ashore the Yellowstone River in Montana, launching an investigation into the cause of death.
Although the mortality has yet to be confirmed, park officials speculate the fish died due to proliferative kidney disease (PKD) – a parasite found lurking in the waters.
Biologists on the case have counted around 200 bodies along the river between Big Timber and Livingston.
Incident reports began at the end of August, with the largest group discovered over a nine-mile stretch – a total of 149 dead fish were collected.
Proliferative kidney disease can be spotted by a swollen kidney and spleen, along with pale gills – all of which results in the fish becoming anemic.
The mountain whitefish is a slender silver creature found in the rivers and streams of Yellowstone, and favors deep pools and clean, clear water.
Park officials note that this fish is also very sensitive to pollution.
Montana Fish, Wildlife & Parks (FWP) noted that reports of dead fish began to surface at the end of August.
Biologists investigating the deaths have since observed hundreds of more across several areas of the river that stretches 700 miles through Wyoming, Montana and North Dakota.
The team spotted seven in one day over about nine miles from the Springdale Bridge Fishing Access Site to the Grey Bear Fishing Access Site, upstream from Big Timber.
The following day, 149 dead whitefish were found between the Pig Farm Fishing Access Site and the Springdale Bridge Fishing Access Site, downstream of Livingston.
And then they counted 38 dead whitefish over 20 miles between the Pine Creek Fishing Access Site and the Highway 89 Bridge Fishing Access Site, upstream from Livingston.
‘FWP will continue to monitor conditions on the Yellowstone River,’ the statement reads.
‘At this time, no closures or restrictions are expected for the Yellowstone River or its tributaries.
A similar incident occurred in 2016 at the park that forced officials to close a 183-mile stretch of the Yellowstone River.
However, at this time there were thousands of dead fish washing up on the shore.
‘This kill is unprecedented in magnitude. We haven’t seen something like this in Montana,’ Fish, Wildlife and Parks spokeswoman Andrea Jones said in 2016.
Wildlife officials have documented more than 2,000 dead mountain whitefish and believe the total number killed is in the tens of thousands.
The closure was put in place to stop fishing, rafting and other activities prevent the spread of the parasite, which may be the solution to the current problem if the death toll continues to rise.
DailyMail.com has contacted Montana Fish, Wildlife & Parks for comment and has yet to receive a response.