Four species of native fish are listed as endangered under the Endangered Species Act (ESA) in the Colorado River basin in the State of Colorado. A Recovery Program has been established to fulfill the goal of bringing populations of these four endangered fish back to self-sustaining levels. Recovery Program efforts may affect stream flow regimes and reservoir operations throughout the West Slope of Colorado. The four fish are the humpback chub (Gila cypha), the bonytail (Gila elegans), the razorback sucker (Xyrauchen texanus) and the Colorado pikeminnow (Ptychocheilus lucius,formerly called the Colorado squawfish.) These are warm water fish, residing primarily in lower elevation stretches of the Colorado River west of Rifle, on the White River in Rio Blanco County and in the Yampa River in Moffat County.