ALPINE, Wyo. — The Wyoming Game and Fish Department (WGFD) has identified the reason behind a widespread fish die-off in the Salt River between the Salt River Range and the Palisades Reservoir: Proliferative Kidney Disease (PKD).
A Wednesday news release from WGFD stated that the disease is triggered by a microscopic parasite called Tetracapsuloides bryosalmonae. Current findings show that mountain whitefish are the primary species affected by this PKD outbreak. The agency’s Fish Health Lab conducted specialized laboratory tests on fish from the river and confirmed the presence of the parasite and evidence that the mortality was caused by the parasite.
“This event marks the first documented instance of a PKD outbreak causing significant fish mortality within Wyoming,” WGFD Jackson Region Fisheries Supervisor Darren Rhea said in a statement. “While it is difficult to get an exact count, we suspect that total mortality may number in the thousands.”
The Salt River remains open for fishing and recreation at this time, according to WGFD. However, the agency could implement emergency closures if fish continue to die at a rate that threatens long-term river health. Anglers are encouraged to fish in other areas, if possible, to reduce stress on the Salt River’s fish during this period.
Outbreaks of this disease have been documented previously in neighboring states, including Idaho and Montana. In 2016, an outbreak occurred on the Yellowstone River, resulting in a large-scale fish mortality event that temporarily closed the river. According to a 2023 research article in the International Journal for Parasitology, PKD is more likely to emerge in warm water temperatures. There is no confirmed correlation at this time, though area river temperatures soared in late July and early August.
Research is being conducted across the region to better understand the relationships between “various organisms and the environmental triggers that lead to severe clinical symptoms in fish populations.” Jackson Region fisheries managers have long-term data from the Salt River, and biologists plan to conduct follow-up surveys next year to assess the overall impact on whitefish populations.
WGFD asks recreationists to do their part to prevent the spread of diseases and invasive species: Clean, drain, and dry all watercraft and gear between trips, and never move live fish from one body of water to another.
