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Nonnative Trout

Brook trout capture
Hoop nets containing enclosures seeded with mature brook trout were effective in capturing large numbers of adult brook trout

Non-native trout have been extensively stocked in many lakes and streams for recreational fishing. Considerable published information now exists to demonstrate that non-native trout have caused altered aquatic ecosystems and displaced native species.

Studies conducted by Pacific Southwest Research Station scientists in high elevation lakes in the Sierra Nevadas and in the Klamath-Siskiyou Wilderness Areas have demonstrated that trout have caused major changes in abundance and distribution of native amphibians, zooplankton, and benthic invertebrates, which threaten the future survival of some species. Moreover, amphibian declines caused by trout introductions have led to declines in predators that rely on these species as prey (example: the mountain garter snake, the only snake native to high elevation ecosystems).

Thus, trout introductions have resulted in major disruption and cascading effects throughout the ecosystem. When trout are not native to aquatic ecosystems, and their introductions result in substantial environmental changes, they can be considered invasive species. Future work will target developing ways to manage fish stocking to minimize deleterious effects and restore native species.

Non-native fishes, such as brook trout, brown trout, and rainbow trout, were introduced to the Rocky Mountain region to promote recreational fishing, with similar effects on aquatic communities throughout the Inland West. Changes in aquatic systems produced by climate change also suggest that large numbers of non-native coldwater fishes and other kinds of invasive aquatic organisms — crayfish, mussels, amphibians, macroinvertebrates, and nonindigenous pathogens — will become issues in the future. The Rocky Mountain Research Station has identified priority research topics for aquatic invasives and is exploring the interacting effects of Cutthroat Trout and Climate.