The mountain sucker (Catostomus platyrhynchus) is a sucker found throughout western North America, on both sides of the Rocky Mountains, including the upper Missouri River, Columbia River, Sacramento River, and Colorado River. It is not limited to higher altitudes but is known from locations as high as 2,800 m (9,200 ft). It is a slender, streamlined fish typically under 20 cm (8 in) in length. It is generally olive green or brown above, with pale underparts, and breeding males have a lateral red-orange band and fins suffused with the same color. It is mainly herbivorous, feeding on algae and diatoms. Breeding takes place in late spring and early summer in gravelly riffles in small streams.