Overview
The Flannelmouth Sucker (Catostomus latipinnis) is an iconic native big-river fish of the Colorado River system, famed for navigating the roaring whitewater rapids and deep desert canyons of the American West. It takes its descriptive common name from its enormous, fleshy, velvety lobed lips, which resemble heavy flannel fabric and function as an exquisite tactile organ for grazing on algae and aquatic insects.
Biology and Physical Characteristics
The Flannelmouth Sucker has an elongated, cylindrical body with a slender caudal peduncle and large, sickle-shaped fins. Its coloration ranges from olive-green to yellowish-brown on the back with pale golden flanks and a cream-colored belly. Its defining feature is a colossal, downward-facing subterminal mouth with exceptionally broad, fleshy lips covered in dense papillae, with the lower lip deeply divided into two large, pendulous lobes.
Behavior and Ecology
A powerful swimmer adapted to sediment-laden, turbulent desert rivers, the Flannelmouth Sucker migrates dozens of kilometers each spring to spawn over shallow gravel shoals in tributary mouths. It uses its heavy flannel lips to vacuum thick films of periphyton algae and stonefly larvae off slippery canyon boulders in roaring currents.
Conservation and Human Impact
Assessed as Least Concern globally, the Flannelmouth Sucker has been eliminated from significant portions of its historical lower Colorado River range due to cold-water hypolimnetic releases from Glen Canyon and Hoover dams, channelization, and predation by invasive gamefish like smallmouth bass and striped bass.
Interesting Factoid
The Flannelmouth Sucker’s lips are so enormous, fleshy, and velvety that early river explorers thought they looked like thick flannel cloth, perfectly designed for vacuuming slick canyon rocks in roaring rapids.