Several streams in the Trout Creek Mountains are home to trout, including the rare Lahontan cutthroat trout subspecies. These include Willow Creek, Whitehorse Creek, Little Whitehorse Creek, Doolittle Creek, Fifteen Mile Creek, Indian Creek, Sage Canyon Creek, Line Canyon Creek, and some tributaries of McDermitt Creek. Lahontan cutthroat trout live in small, isolated populations that are often confined to individual streams, many of them in the Trout Creek Mountains. These populations have significant genetic differences due to their history of isolation. For most of the 20th century, the trout's numbers declined considerably. It was listed under federal law as an endangered species in 1970 and was reclassified as threatened in 1975. Reasons for the fish's decline included habitat degradation from cattle grazing, drought, overfishing, competition with other fish, and hybridization with introduced rainbow trout, which decreased the number of genetically pure Lahontan cutthroat trout. However, reductions in cattle grazing in riparian zones since the 1980s allowed fish habitat and populations to start to recover.