Endangered fish recovery resumes

The Upper Colorado River Endangered Fish Recovery Program has resumed its work in sections of the Colorado, Duchesne, Green and Yampa rivers in Utah and Colorado.

The program is intended to help recover four species of endangered fish — the humpback chub, bonytail, Colorado pikeminnow and razorback sucker.

Biologists from the Utah Division of Wildlife Resources, U.S. Fish and Wildlife Service, Colorado Division of Wildlife and Colorado State University will combine their efforts on the program.

Management of non-native fish species is a primary goal of this year's research work. Northern pike and smallmouth bass have been identified as two non-native fish species that pose a significant threat to endangered species of fish and other native fishes.

Northern pike and smallmouth bass are active predators that eat other fish and compete for food and space in the river.

For nearly a decade, the program's researchers have worked to reduce the populations of these non-native fish species to a level where endangered and other native fishes can continue to co-exist and thrive.

"Although we still have a long way to go to manage non-native fishes in critical habitat in the Upper Colorado River Basin, we are encouraged by data that indicate we are making progress, especially with northern pike," said Bob Muth, recovery program director.

"We've seen a shift from large-sized, adult northern pike in a 70-mile reach of the Yampa River to smaller, juvenile fish. Last year, we noted that the overall abundance of northern pike in the Yampa neared its lowest level since our management efforts began in 1999."

Reductions of adult northern pike populations have also occurred in critical habitat areas of the Green River. Since the program's removal efforts began in 2001, northern pike numbers have decreased by more than 90 percent.

Management of smallmouth bass populations remains a problem, as researchers noted strong reproduction in 2006 and 2007 in sections of the Green and Yampa rivers. In 2008, the entire Upper Colorado River Basin experienced a return to higher and cooler water flows, and smallmouth bass reproduction diminished greatly in all rivers.

Efforts to remove smallmouth bass in 2007 and 2008 in the Yampa and Green rivers showed limited success. However, smallmouth bass populations on the Colorado River declined for the third consecutive year. This year, removal efforts will continue and crews will coordinate their sampling trips to address the movement of smallmouth bass.