The Razorback sucker was once common throughout the Gila River watershed regions of Arizona. Commercial fishing together with dam building decimated the fish stock, which were unable to breed due to lower water temperatures in the reservoirs while dams blocked their movement into smaller channels (Nabhan 1988:553). They are now federally listed (USFWS October 23, 1991) as an endangered species with provisions for the protection of its critical habitat. Ongoing conservation efforts are taking place throughout the Upper and Lower Colorado River Basins. The largest and most genetically-diverse population is found in Lake Mohave, Arizona/Nevada border.