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FWP continues monitoring effort on Yellowstone, no restrictions or closures planned


Thursday, August 24, 2017

Monitoring floats on the Yellowstone River in the Paradise Valley on Thursday turned up 19 more dead mountain whitefish.

Additionally, Montana Fish, Wildlife and Parks’ crews discovered 1 moribund fish, which are live fish close to death. Moribund fish are important for histology testing to determine the cause of mortality.

Thursday’s monitoring floats follow similar efforts Monday and Tuesday on the Yellowstone between Livingston and Springdale. These floats turned up 76 dead whitefish, two dead suckers and one dead brown trout.

Official test results won’t be available until next week at the earliest and biologists don’t have enough information yet to determine the cause of these localized and limited fish kills.  

“We’re still collecting information at this point,” said Travis Horton, Region 3 fisheries manager. “We aren’t currently considering any closures or restrictions. However, we ask that anglers not target mountain whitefish.”

On Friday, FWP crews are planning to again search the stretch between Livingston and Springdale where they’ve found the bulk of the dead fish.

Thursday’s monitoring float focused on the stretch of Yellowstone from Grey Owl Fishing Access Site to Pine Creek. This stretch was hardest hit last summer by proliferative kidney disease, or PKD. In 2016, upwards of 1,900 dead mountain whitefish were found on one bank of the river.

PKD is caused by a microscopic parasite that exists in the river year-round. Though the reason the parasite will suddenly cause PKD is unknown, high water temperatures, low flows and general fish stress can be factors.

Last summer the PKD outbreak on the upper Yellowstone River led to an emergency closure by FWP and the death of thousands of mountain whitefish, which are native to the river. Historically low flows in the river coupled with high water temperatures last summer helped to exacerbate the impacts of PKD on whitefish.

Conditions this year are much different – water temperatures have remained cooler and flows are above average. In addition, the time of year is later with longer, cooler nights. These environmental differences could result in a much different scenario and outcome compared to last year’s fish kill.