Flannelmouth Sucker, Catostomus latipinnis
Flannelmouth Sucker, Catostomus latipinnis. Fish caught from the San Juan River, Farmington, New Mexico, October 2023. Length: 29 cm (11 inches). Catch, photograph and identification courtesy of Chris Moore, Peoria, Arizona.
Flannelmouth Sucker, Catostomus latipinnis. Fish caught from the San Juan River, Farmington, New Mexico, October 2023. Length: 51 cm (20 inches). Catch, photograph and identification courtesy of Chris Moore, Peoria, Arizona.
Flannelmouth Sucker, Catostomus latipinnis. Fish caught from the San Juan River, Farmington, New Mexico, October 2023. Length: 53 cm (21 inches). Catch, photograph and identification courtesy of Ben Cantrell, Sebastian, Florida.
The Flannelmouth Sucker, Catostomus latipinnis is a member of the Sucker or Catostomidae Family and is known in Mexico as matalote boca de franela. Globally, there are twenty-eight species in the genus Catostomus, of which seven are found in all freshwater systems of Mexico.
The Flannelmouth Sucker has a cylindrical elongated body that tapers gradually to the rear. Juvenile fish are silvery in color that transition to light gray, tan or greenish-brown dorsally and lighter ventrally with maturity. Some fish have dark blotches on the under sides and some fish are uniformly dark dorsally. Both sexes of breeding fish have orange fins. Their head is short, thick, rounded above and flat below with horizontal mouth that has a large lower lip with thick and flesh lobes. They have large fins. They have 20 to 44 gill rakers on the first fill arch. Their and fin has 7 rays and their dorsal fin has 10 to 14 rays. Their lateral line is complete and they are covered with small scales.
The Flannelmouth Sucker are found at depths up to 6 m (20 feet) within the rocky pools, runs, riffles, and backwaters of medium to large freshwater rivers, and less often in small rivers and creeks with large amounts of cover and shade during daylight hours. They are absent from impoundments. Young usually are in shallower water faster flowing waters than are adults and will enter cold hypolimnetic water released from major dams that makes them more susceptible to predation by game fish. They have a thermal tolerance of up to 32°C (90°F). Spawning occurs in riffles, margins of rapids, or in low-gradient mouths of tributaries, usually over a substrate of coarse gravel or gravel-cobble. Young suckers that exit warm tributaries and enter cold hypolimnetic water released from major dams may experience increased susceptibility to predation by rainbow trout and other predators. They are one of the largest suckers and reach a maximum of 56 cm (22 inches) in length and 920 g (2 lbs 0 oz) in weight. They are bottom feeding herbivores and omnivorous that consume diatoms, algae, plant fragments, see and benthic invertebrates. Sexual maturity is reached in 4 to 7 years. Reproduction involves spring migrations to shallow water up stream. Released eggs are quickly externally fertilized by males, become sticky, and adhere themselves to rocky structure. Once hatched the larvae are carried downstream as they mature. Their lifespan is unknown. In general, the Flannelmouth Sucker is poorly studied with very limited information available about their lifestyle and behavioral patterns including specific details on age, growth, longevity, movement patterns, diet, habitat use, and reproduction.
The Flannelmouth Sucker has historically been found in the Colorado River system of the western United States and northern Mexico in the state of Sonora. There are several reports that they have now been extirpated in Mexico, however there are also literature suggestions that this needs to be validated.
The Flannelmouth Sucker is similar to the Little Colorado Sucker, Catostomus Sp., juvenile and hybrids of the Razorback Sucker, Xyrauchen terxanus and the Sonora Sucker, Catostomus insignis, but can be distinguished by their very large lower lips.
From a conservation perspective the Flannelmouth Sucker is currently considered to be of Least Concern with stable widely distributed populations. There have been significant declines in both numbers and distribution within their southern range that is attributed to the building of impoundments, flow alterations, habitat loss and predation by the introduction of non-native game fish. They are known to hybridize with the Razorback Sucker, Xyrauchen terxanus and the introduced White Sucker, Castostomus commersoni. They have also been eradicated by programs to remove trash fish. They are pursued as a game fish at a nominal level. They have been designated as a Species of Greatest Conservation Need in the state of Arizona and are included in several multi-state conservation plans.