FWP: Parasite that closed Yellowstone River could persist for years

LIVINGSTON — The closure of the Yellowstone River and all its tributaries to all recreational activities continues until further notice following identification of a parasite contributing to a mountain whitefish die-off.

Montana, Fish, Wildlife and Parks has also recently received reports of the kill beginning to affect some rainbow and Yellowstone cutthroat trout, according to information released by FWP. 

FWP will hold a public town hall meeting in Livingston at 6 p.m. on Wednesday at the Park County Fairgrounds. 

FWP officials will provide information on fish kill and closures and answer questions. 

FWP closed the Yellowstone River, as well as all named and unnamed rivers and streams that flow into it, from Gardiner to near Laurel on Friday morning after tests revealed a microscopic parasite was contributing to the die-off of tens of thousands of native mountain whitefish.

The closure was put in place to help limit the chance of the spread of the parasite to adjacent rivers through boats, tubes, waders and other human contact and minimize further mortality in all fish species.

Removing human activity in the impacted area also allows fish to take refuge in pools without additional stressors, which gives them the best chance of survival, according to FWP. 

The parasite, along with additional fish health stress from high water temperatures, near-record low-water flow, and disturbances caused by recreational activity, is responsible for the fish kill, Eileen Ryce, FWP fish hatchery bureau chief and supervisor of the Fish Health program, said Monday. 

There are several strains of the parasite, called Tetracalsula bryosalmonae, which causes Proliferative Kidney Disease in whitefish and can sometimes affect other fish with varying degrees of severity, Ryce said. 

But it’s early in the fish kill and much more information must be gathered, she said. 

Where the parasite came from is still a mystery that may never be solved, Ryce said. It’s found in rivers in Europe, Canada and the American Northwest. Most of the written information about the parasite is from research conducted in Europe. 

Once the parasite is in a watershed, it tends to persist, but often the worst of the fish kills happen in the first few years and then can gradually subside, Ryce said. 

But it’s too soon to tell, she emphasized. 

“Different strains seem to have different infection and susceptibility rates,” Ryce said, adding that environmental stress can exacerbate susceptibility. 

In Montana, the disease has been documented previously in two isolated locations in central Montana over the past 20 years. Recent outbreaks have occurred in Washington, Oregon and Idaho. In trout, research has shown the disease to have the potential to cause 20 to 100 percent mortality, the FWP update stated. 

And for anyone who might have fish in their freezers from before the die-off, those fish are safe for human consumption if cooked according to standard safe food handling instructions, the FWP fact sheet stated.

FWP spokeswoman Andrea Jones said FWP’s informational campaign to combat aquatic invasive species, “Clean, Drain, Dry,” is especially important now. 

Mandatory boat-cleaning stations were in place this weekend east and west of Livingston, Jones said, with additional sites on other area rivers likely in order to protect other watersheds. 

The fish kill extends from the northern boundary of Yellowstone National Park at Gardiner to Grey Bear Fishing Access Site, west of Big Timber — nearly 100 river miles.

The stretch of the Yellowstone from Loch Leven Fishing Access Site north of Emigrant to Springdale, east of Livingston, appears to be the hardest-hit area at this time.

So far, fish inside Yellowstone National Park have not been documented to be affected, the FWP fact sheet stated. 

FWP encourages the public to contact the agency with reports of multiple dead fish found outside of the identified area of impact or dead trout found in any location.

On Sunday between Livingston and Gardiner, the river was barren of drift boats and rafts. Fishing access sites, where parking lots typically overflow with trailers and cars, sat empty.