The flannelmouth sucker, Catostomus latipinnis, is a freshwater fish species found primarily in the Colorado River basin and its associated tributaries across the southwestern United States and northern Mexico. It is a relatively large-bodied fish belonging to the family Catostomidae, commonly known as suckers. It has adapted to the dynamic conditions of large river systems in arid regions.
Physical Characteristics
The flannelmouth sucker has distinct physical attributes. It has a long, thick body that tapers towards the tail, with a relatively short and thick head. A prominent feature is its fleshy mouth, particularly the enlarged lower lip, which is how it earned its common name.
This fish has large fins but relatively small scales. Its coloration ranges from dark brown to greenish, fading to orange or yellow on its sides, with a lighter, almost white underside. During the spawning season, males exhibit a more vibrant orange hue and develop small, pearl-like bumps called tubercles on their anal and caudal fins. Adults reach lengths of up to 28 inches and weigh as much as 8 pounds, making it one of the largest species within its genus.
Natural Habitat and Life Cycle
Flannelmouth suckers are native to the freshwaters of Arizona, Colorado, New Mexico, Nevada, Wyoming, and Utah, and historically occurred in California. These fish prefer larger rivers and deep riffles and runs, although they can also be found in smaller streams and occasionally lakes. Young flannelmouth suckers, or larvae, inhabit shallow areas or slower current velocities like backwaters, eddies, and side channels. Adult flannelmouth suckers, conversely, seek deeper waters that provide ample cover and shade during daylight hours.
The diet of the flannelmouth sucker is omnivorous. They are benthic feeders, meaning they forage near the river bottom, consuming detritus, mud, inorganic substances, planktonic organisms, and algae. Spawning occurs in the spring and early summer, from March through July, when water temperatures reach around 13-18 degrees Celsius (55-64 degrees Fahrenheit). Females release adhesive, demersal eggs over sand and gravel bars in shallow water, where they are then fertilized by males. After hatching, the larvae drift downstream with the current as they mature.
Conservation and Ecological Role
While the flannelmouth sucker is not currently listed as endangered by the IUCN, its populations have been declining, prompting its designation as a sensitive species in Nevada and a species of special concern in Utah. A primary threat to this species is habitat alteration, particularly the construction and operation of hydroelectric dams. These dams modify river flows and temperatures, creating cold, clear tailwaters that are unfavorable for native fish reproduction and survival. Blockage of migration routes by dams also affects spawning grounds.
Another significant challenge comes from non-native species, which prey on or compete with flannelmouth suckers. Hybridization with introduced suckers, such as white suckers and bluehead suckers, also poses a genetic threat to flannelmouth populations. The flannelmouth sucker plays a significant ecological role; its sensitivity to water quality and environmental conditions makes it an indicator species for the overall health of rivers like the Green River and San Juan River. Conservation efforts, such as the Grand Canyon Protection Act of 1992, aim to regulate water releases from dams to mitigate negative impacts on their habitats.