HELENA, Mont. – Montana Fish, Wildlife and Parks is destroying half a million hatchery trout because of disease concerns.

In a press release Friday, the department said that a temporary loss of power May 12 had affected control and monitoring of water levels behind the Rainbow Dam Reservoir. Officials have no way to confirm Missouri River water didn’t enter an area of the adjacent Giant Springs Fish Hatchery where 450,000 rainbow and 50,000 brook trout were housed. The river is infected with a parasite that can kill young trout and possibly with other pathogens.

Trout from U.S. Fish and Wildlife Service and other state hatcheries will replace the Giant Springs trout, which are used to stock waters across Montana.

Once the fish are destroyed, Giant Springs hatchery areas will be disinfected.