The razorback sucker, which has declined in abundance in the upper Colorado River primarily because of man's impact on the environment, has been recommended for listing as "threatened" in the U.S. Department of Interior's list of threatened or endangered species. During the present investigation, razorback suckers were nevertheless found in relatively large concentrations at two restricted locations -- the mouth of the Yampa River and a flooded gravel pit connected to the Colorado River near Grand Junction, Colorado.