Idaho fought invasive lake trout; a decade later adult numbers were down 64%

An aggressive campaign using commercial nets and angler bounties helped turn around a decade-long fight against non-native predators in northern Idaho’s largest lake. By 2016, ten years after the Idaho Department of Fish and Game (IDFG) began its suppression programme on Lake Pend Oreille, the number of adult lake trout had fallen by 64 per cent. According to research published by the United States Geological Survey (USGS), the sharp drop in lake trout allowed native rainbow trout and landlocked sockeye salmon, known locally as kokanee, to recover. For decades, Lake Pend Oreille was known for producing world-record trophy trout. But the accidental introduction and rapid spread of non-native lake trout (Salvelinus namaycush) later threatened the entire food chain. Lake trout feed heavily on kokanee salmon, which are a key food source for native bull trout and the lake’s prized Gerrard strain rainbow trout.