The desert sucker or Gila Mountain sucker (Catostomus clarkii), is a freshwater species of ray-finned fish in the sucker family, endemic to the Great Basin and the Colorado River Basin in the United States. It inhabits rapids and fast-flowing streams with gravelly bottoms. It is a bi-colored fish with the upper parts olive brown to dark green, and the underparts silvery-tan or yellowish. The head is cylindrical, tapering to a thick-lipped mouth on the underside. This fish can grow to 31 in (79 cm) in Arizona but is generally only about half this size elsewhere. There are three subspecies, found in different river basins, and some authorities allot this species its own genus Pantosteus.