Idaho poisoned the Snake River to kill an invasive mussel. Some call the results ‘heartbreaking’

The invasive quagga mussels found in an Idaho river in 2023 were microscopic. But to state officials, their presence was enormous.

Though the mussels couldn’t grow much larger than a nickel, state officials said an infestation would devastate Idaho’s economy and ecosystem, clogging water pipes and stealing food from native species. Biologists typically kill off the mussels with chemicals, adding just enough of a lethal dose to infested waters. But treating mussels in a river had never been done before. Moving water would let the toxic chemicals travel beyond the treatment area.

State officials took the risk.

Only two weeks after that first mussel detection, the state spent $3 million to flood the Twin Falls area of the Snake River with over 40,000 pounds of the prescribed copper-based p