Native fishes of the upper Colorado River UCR basin are declining in abundance. Alteration of the natural riverine environment during the last 100 years by human actions including physical alterations and the introduction of nonnative species. Changes in the physical and biological characteristics of riverine habitat have contributed to the endangerment of four native fish species Colorado (pikeminnow, humpback chub, bonytail, and razorback sucker)....

Surveys of the Colorado River near Grand Junction, Colorado show that populations of Colorado squawfish (Ptychocheilus lucius) and razorback sucker (Xyrauchen texanus) are small and continue to decline. A potentially important factor in their decline is a reduction in the amount of available habitat. The fish are most commonly found in habitats of complex channel which may be affected by bank stabilizing activities and regulation of the river flow....