According to Explore Big Sky, the Montana Fish Wildlife and Parks (FWP) closed the Yellowstone River and its tributaries on August 19, 2016. The bryozoan releases parasite spores into the river which enter the fish through its gills, Eileen Ryce, an FWP fisheries biologist, explained.
The FWP officials spoke to a crowd of about 50 people - anglers, local lawmakers, the media and business owners - at a fishing access site where the stench of dead whitefish rotting on the riverbank wafted through the air. The ban includes all river activities, including fishing and rafting.
This combined with near-record low water flows, summer high temperatures and recreation activities has worsened the situation.
Readers may remember reading about Laurie, Labrador Oscar and I traveling to Yellowstone National Park over the July 4th weekend and spending a couple nights at Chico Hot Springs resort near Emigrant.
Sheppard is calling it a crisis, putting it in simple terms, he says that a pet owner cannot even throw a stick into Yellowstone River; the situation is that serious.
According to experts, they are still trying to find out whether the parasite infestation has also affected other parts of Yellowstone River downstream as well as its primary tributaries.
The most recent major die-offs have been in eastern Idaho on the South Fork of the Snake River and the Henry's Fork in eastern Idaho, where the parasite was first discovered in 2011 and is said to be causing substantially fewer fish kills each year.
"We've got to get to the bottom of it", Senator Steve Daines said.
"We're not looking at it being a permanent closure", said Jeff Hagener, FWP director.
Reports of the Yellowstone river fish kill began pouring in more than a week ago.
"What we mean by that is that the immune response that the fish are expressing would suggest that they have not been exposed to this parasite previously", she said. However, Dave Moser, a biologist with FWP fisheries, says that the microscopic organism was from other waters, most likely, carried in from unclean boats that were not drained and dried properly, possibly even from waders. According to news accounts, the parasite has been seen in Washington, Oregon, Idaho, Canada and Europe. "Why that's a concern is that the sheer volume of parasites that's out there makes it very easy for the parasite to be spread to other waters".
Fish, Wildlife and Parks spokeswoman Andrea Jones said that the entire week, crews are going to collect fish on the Yellowstone downstream of Springdale and on tributaries, including Boulder, the Shields, and Stillwater rivers.
"That's something we can't say, but we can help them understand why it is closed to this extent", she said. In other rivers, outbreaks of the disease persisted until water temperatures dropped months later. However, if the fish are given time to adapt they may build up some immunity to the parasite and recover.