The Idaho Department of Fish and Game says biologists have confirmed thousands of dead whitefish on the South Fork of the Snake River in southeastern Idaho.
Biologists suspect it's an outbreak of proliferative kidney disease, the same pathogen responsible for killing thousands of whitefish in the Yellowstone River last month and which prompted the temporarily closure of large sections of that acclaimed river in Montana.
The same disease was responsible for whitefish die-offs on the South Fork of the Snake River in 2012.
The agency said in a news release Friday the outbreak is unlikely to affect the river's overall fish population.
It said fisheries biologist Brett High boated a stretch of the river and saw thousands of dead white fish in eddies and along the banks, mostly in the upper river.
High said they also confirmed that "healthy whitefish and trout are still very abundant, and only a small percentage of fish showed signs of disease."