For generations, the management mindset of our national parks maximized quantity over quality- give as many people the opportunity to encounter wildlife, regardless of the quality of the experience. For anglers, this meant stocking loads of non-native species- mostly brook, brown, and rainbow trout- that competed with natives for space and resources.
Whether wolves or native trout, when you remove species from a landscape the ecosystem becomes unstable, less resilient to disturbance. Since the 90’s, priorities at the National Park Service (NPS) have shifted towards restoring native landscapes and their associated ecological funding. Undoing damage in aquatic ecosystems has been slower to take hold, but Glacier National Park staff have recently have recently implemented plans to restore native westslope cutthroat and bull trout to creeks within the park. Both species have been largely eliminated from their native range in the intermountain west, both are indicators of high-quality aquatic habitat, and both are a prey item for innumerable organisms within their native ecosystems. Read more about the project here.