Greenhorn Creek is a tributary to the upper Ruby River. In 2013, a fish barrier was constructed in the lower reaches and non-native trout were removed from above the barrier using piscicides. In 2016, genetically pure westslope cutthroat trout from six adjacent drainages were used to repopulate the stream. It is currently estimated that over 15,000 genetically pure westslope cutthroat trout occupy the 26 miles of Greenhorn Creek and its tributaries above the barrier.