The Santa Ana sucker (Catostomus santaanae) is a freshwater ray-finned fish, endemic to California. It is closely related to the mountain sucker and has dark grey upper parts and silvery underparts. It grows to a maximum length of 25 cm (10 in), but most adults are much smaller than this. It feeds on algae, diatoms and detritus on the floor of shallow streams with sand, gravel or cobble bottoms. It is found in only a few streams in southern California, and many of these in the Greater Los Angeles metropolitan area have been restricted to concrete channels. Because of its small area of occupancy and vulnerability, the International Union for Conservation of Nature has rated this fish as "endangered".