The upper Colorado River endangered fish recovery program will focus on northern pike, smallmouth bass and channel catfish in an experimental nonnative fish management project this spring and summer to determine if populations of these species in certain river reaches in Colorado and Utah can be reduced to a level that will enable endangered and other native fishes to coexist and thrive.
Biologists believe these nonnative fish species pose a significant threat to the endangered humpback chub, bonytail, Colorado pikeminnow and razorback sucker.
In Utah, work is currently underway on the Duchesne River and the White River. A more extensive project will take place from mid-July through mid-August in the Desolation and Gray canyons of the Green River.
Detailed information about the Green River project will be presented at public regional advisory council meetings May 19 in Vernal and May 20 in Green River.
Those with questions may also contact the Utah Division of Wildlife Resources.
"Nonnative fish have been identified as one of the factors limiting recovery of the native fish of the Colorado River Basin, including the Green River in Utah," stated Matthew Andersen, native aquatic species coordinator for the Utah DWR.
"Many researchers have identified nonnative fish as a threat to natives because they prey on native species, especially young natives. The nonnative fish also compete with the natives for food."
In the Green River and its tributaries, channel catfish and northern pike are especially harmful.
"Both species are aggressive predators who can consume many native fish in their lifetime," continued Andersen.
"Because the native fish did not evolve in a system that included these predators, they don't have the natural defense mechanisms needed to help them survive."
Andersen says it is unlikely all of the nonnative fishes could ever be removed from such an extensive system, but biologists hope active removal efforts will help native fish produce offspring, and that the offspring will have a greater chance of surviving in a habitat with fewer nonnative fish.
In eastern Utah, biologists will establish experimental treatment and control sections in the Green River in Desolation and Gray canyons.
On the Duchesne River between Myton Diversion and the Green River confluence and the White River (in Uintah County) from the Colorado state line to the Green River confluence a similar experiment will be performed.
In treatment sections, targeted nonnative fish species will be removed. In control sections, targeted nonnative fish species will be captured, marked or tagged and returned to the river.
Follow-up sampling will determine if management efforts reduced the numbers of targeted nonnative fishes in sections where they were removed. Monitoring of endangered and other native fishes will determine if numbers of these species increase.