Colorado River Native Fish Population Increasing

December 5, 2005 -- Efforts to increase the native fish population in the Colorado River by removing non-native fish are working, according to fish removal crews. More than 17,000 non-native fish have been captured and killed this year.

The process involves sending a 5,000-watt pulse into the water and scooping out the temporarily stunned fish. Native fish are scanned for IDs or tagged and released near the Little Colorado River confluence by teams of biologists and volunteers. Non-native trout are killed and used as fertilizer at a downriver Indian reservation. Warmer weather could also help account for increased native fish populations, according to Clay Nelson, an Arizona Game and Fish Department biologist.

Several National Research Council reports address issues related to non-native species. Downstream: Adaptive Management of Glen Canyon Dam and the Colorado River Ecosystem identifies specific improvements for the Grand Canyon Monitoring and Research Center and areas of study, including the role of non-native species in the ecosystem. Endangered and Threatened Fishes in the Klamath River Basin: Causes of Decline and Strategies for Recovery and Atlantic Salmon in Maine examine how to help endangered native fish, including decreasing competition from hatchery-grown and non-native fish. Nonnative Oysters in the Chesapeake Bay discusses the risks in introducing disease-resistant Sumino oysters from Asia to offset the decline of native oysters in the Chesapeake Bay.

• Downstream: Adaptive Management of Glen Canyon Dam and the Colorado River Ecosystem 1999
• Endangered and Threatened Fishes in the Klamath River Basin: Causes of Decline and Strategies for Recovery 2004
• Atlantic Salmon in Maine 2004
• Nonnative Oysters in the Chesapeake Bay 2004

• Arizona Game and Fishing Commission
• Colorado Division of Wildlife
• Utah Division of Wildlife Resources