Nonnative Fish in Lake Powell
Nonnative Fish in the Colorado River below Glen Canyon Dam
Rainbow trout (Oncorhynchus mykiss) were stocked in the water released from the dam in the Lees Ferry area in the 1970’s. Native fish are unable to reproduce in the cold water released from the dam, but rainbow trout have flourished. Now, the 15-mile stretch from the Glen Canyon Dam to Lees Ferry is a world-famous rainbow trout fishery.
In 2014, Glen Canyon NRA and Grand Canyon NP collaborated with partners, especially Arizona Game and Fish, to develop the Comprehensive Fisheries Management Plan. This plan established goals and evaluated alternatives to managing the rainbow trout fishery to keep the population healthy, with high catch rates and large fish, while also protecting and enhancing native fish populations in Grand Canyon.
In recent years, the brown trout populations have expanded in the Lees Ferry reach to levels much higher than seen in the past. Brown trout are predatory on rainbow trout and are demonstrated to have negative impacts on native fish, including the endangered humpback chub. Examples exist where brown trout have displaced rainbow trout fisheries. More information on the management of brown trout to save the rainbow trout fishery is available at the Lees Ferry Fisheries Monitoring link below.
Green sunfish exist in Lake Powell and occasionally survive passing through the dam. Green sunfish are highly predatory and have been shown to impact native fish populations in other waters. Some backwater areas in the river below the dam warm in the summer enough that green sunfish can reproduce. The NPS has partnered with other agencies to removed green sunfish populations in backwaters and develop long-term strategies to prevent green sunfish and other non-native warm-water fish from establishing below the dam and impacting native fish.
The river below the dam and into Grand Canyon is considered sacred by several Native American tribes. Fisheries management activities can be offensive, especially when many fish must be killed. To mitigate the negative tribal impact from taking fish in management actions, the NPS and partners identify beneficial uses for the removed fish. Most commonly the fish are provided to a tribal aviary to feed injured eagles.