Whitefish mortality observed in upper Yellowstone River 

Initial test results indicate PKD as likely cause 

LIVINGSTON – Montana Fish, Wildlife & Parks fisheries biologists are monitoring an area of the Yellowstone River where several dead mountain whitefish have been observed.  

Anglers first reported seeing a small number of dead fish over Labor Day weekend. On Sept. 8, FWP staff floated between the Grey Owl and Mallard’s Rest fishing access sites and observed 57 dead whitefish. They collected several dead and dying fish to submit them for testing.  

Tests that have been completed so far on some of the collected fish indicate they likely died of proliferative kidney disease, or PKD — a condition caused by a parasite affecting salmonids, such as mountain whitefish and trout. PKD has affected fish in the Yellowstone River in recent years, the most significant outbreak happening in 2016. 

Biologists will continue to monitor conditions on the Yellowstone River. No trout mortality was observed during monitoring efforts to date. At this time, no closures or restrictions are expected for the Yellowstone River or its tributaries.  

Anglers can help reduce stress for fish by following these practices when catching and releasing fish, though fish mortality may still occur:  
• Land the fish quickly.  
• Wet your hands before handling the fish.  
• Keep the fish in water as much as possible.  
• Remove the hook gently. Using artificial lures with single and barbless hooks can make hook removal faster and easier.  
• Let the fish recover before releasing it.