From 1886 to 1968, more than 20 million fish were stocked in waters that became Rocky Mountain National Park; in 2026 crews treated 14.3 miles to remove non-native fish and restore threatened greenback trout

For more than 80 years, fish were deliberately introduced into the waters that would become Rocky Mountain National Park. According to the National Park Service (NPS), more than 20 million fish were stocked in waters that are now part of Rocky Mountain National Park between 1886 and 1968, most of them non-native trout. What was once intended to support recreational fishing eventually created challenges for native fish and aquatic ecosystems. In 2026, park managers are working to reverse some of those effects. As part of the Poudre Headwaters Project, crews treated waterways connected to the 14.3-mile Grand Ditch to remove non-native fish and prepare habitat for the recovery of the federally threatened greenback cutthroat trout.

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