Cooperative Fish and Wildlife Research Units Program: Kansas
Education, Research and Technical Assistance for Managing Our Natural Resources

The Upper Colorado River Basin (UCRB) has one of the most threatened fish faunas in the United States (Tyus and Saunders 2000). There are only 14 native fish species in the UCRB and most have declined in their range and abundance in the last 100 years (Carlson and Muth 1989; Valdez and Muth 2005). Native fishes in the Colorado River Basin have been adversely impacted by modifications to natural flow regimes, physical habitat, stream temperatures and other human-induced agents of environmental change, in addition to the negative effects of invasive species. Therefore, the development of criteria for conservation will aid future considerations to protect aquatic species in the basin.