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Thousands of fish are dying by parasite-caused kidney disease in the Salt River south of Alpine in yet another example of an anomalous summer for waters in western Wyoming.
Wyoming Game and Fish announced on Sept. 2 that possibly thousands of fish had died of the parasite that causes “proliferative kidney disease,” or PKD, in mountain whitefish, but spares trout.
“We always assumed we would be maybe a little bit more insulated from it. But then, like everything we’ve experienced this year, this is pretty unprecedented,” said Darren Rhea, Jackson region fisheries supervisor.
While there could be other factors, mass die-offs like this are correlated with stressors such as low flows and warmer water, a result of this year’s drought, Rhea said.
PKD has been documented in other states such as Idaho and Montana; however, this is the first instance of it causing significant fish mortality within Wyoming. A large outbreak in 2016 on the Yellowstone River resulted in temporary river closures.
In 2026, the state has seen a record-low snowpack, record-low lake levels, near-record warm water, and the state’s first voluntary fishing closure on the Snake River and its tributaries.
Anglers alerted Game and Fish to the sight of belly-up fish about three weeks ago. Managers suspected a parasite. Then, the state collected samples, performed some DNA tests with its Fish Health Lab and the Wyoming State Veterinary Laboratory, and confirmed the microscopic parasite –Tetracapsuloides bryosalmonae – was to blame.
The Salt River remains open for fishing, for now. And though the parasite is not dangerous to humans, the state advises anglers to seek other waters to spare fish the added stress. It will continue to track the species to determine impacts.
