A parasite is being blamed for the dead mountain whitefish have been reported from across the Upper Snake Region, including the Henrys Fork, South Fork Snake River, Teton River and main Snake River as far south as Firth. Exactly why these fish are dying had been a mystery until now. Preliminary results obtained by IDFG’s Fish Health Laboratory in Eagle show that a parasite called PKD or Proliferative Kidney Disease may be behind the deaths. This rare parasite has not been documented in Idaho’s wild fish before, although it has been reported in both wild and hatchery trout and salmon in North America and in Europe. This may be the first time the parasite has been detected in any whitefish species. The life cycle of the parasite is not well understood, but involves a freshwater sponge as well as a fish. Transmission and disease signs are linked to elevated water temperatures, which have been common in area waters this summer. There are no known health risks to humans or other warm-blooded animals.