Why are non-native fish so beloved in Montana?

Knapweed and leafy spurge don't have many fans in these parts. Nobody makes the drive from Texas to pose with them and post the photos on Instagram. Invasive species aren't usually something to celebrate, because they can wreak havoc on native ecosystems in ways impossible to undo. But other invaders have gotten a much warmer welcome. One listener wonders why some non-native species – like brown trout and rainbows – are so valued in Montana.