Rio Grande Sucker, Catostomus plebeius
Rio Grande Sucker, Catostomus plebeius. Fish caught within steams of the Jemez Mountains, New Mexico, July 2017. Length: 13 cm (5.1 inches). Catch, photograph, and identification courtesy of Ben Cantrell, San Diego, California.
The Rio Grande Sucker, Catostomus plebeius, is one of the smaller members of the Sucker or Catostomidae Family, and is known in Mexico as matalote del Bravo. Globally, there are twenty-six species in the genus Catostomus, of which nine found in all freshwater systems of Mexico.
The Rio Grande Sucker has a cylindrical or terete shaped body that is flattened. They are brownish-green dorsally transitioning to white ventrally. They have dark blotches along their backs and sides. The sexes are dimorphic with females being larger than males and the breeding males have brilliant black and red stripes on their sides and tubercles on their anal and caudal fins. Breeding females have tubercles on the caudal peduncle. Their head has a broad snout, a very large prominent ventral mouth that is fleshy, subterminal, and protractile that is equipped with pharyngeal teeth. Their anal fin has 7 rays with an elongated base; their caudal in is deeply forked with a deep peduncle; their dorsal fin has 8 to 10 rays and is short and triangular; their pectoral fins have 14 to 15 rays and are bluntly pointed; and, their pelvic fins have 8 to 10 rays and are oval.
The Rio Grande Sucker is found in small to large, middle elevation streams and rivers with rocky pools and gravel and cobble and limited water flow, low turbidity and a high level of aquatic vegetation that have water temperatures of less than 24oC (75oF). The adults are known to collect in glides and pools and they spawn in riffles. They are small in stature reaching a maximum of 20 cm (7.9 inches) with females being longer than males. They have a highly developed sense of hearing, smell, and taste and are omnivorous bottom feeder that primarily consume algae, that they scape off rocks, detritus and aquatic invertebrates. They rely on counter-shading patterns to avoid predation. Reproduction is oviparous and polygynandros (promiscuous). Spawning occurs after spring high water episodes with the water temperature between 11oC (51oF) and 16oC (61oF). It occurs in gravel bars involving one female and two or more males. They spawn in large aggregations with each female broadcasting eggs onto gravel bars and the eggs are simultaneously fertilized by the males. They have lifespans of seven years.
The Rio Grande Sucker is distinguished from other members of the Catostomus Genus by coloration, head and body shape as well as fins and sexual differences.
The Rio Grande Sucker are native to the Rio Grande drainage in the Southwest United States and Northern Mexico. In Mexico they are found in the Pacific drainage in the states of Chihuahua, Durango, Nayarit and Zacatecas. They have been transported outside of their native range to new locations via bait bucket releases and intentional introductions.
From a conservation perspective the Rio Grande Sucker is currently considered to be Data Deficient because the species has declined in the northern part of the range in the United States whereas much of its range is in Mexico with limited information about population trends being unknown. Current populations are estimated to be in excess of 10,000 individuals. In the United States their populations have been in significant decline with a significant reduction in known range which has been attributed to the introduction of non-native species, dam building, habitat degradation including sedimentation, changes in water flow and the addition of herbicides and pesticides to their environment, and the loss and significant aquatic ecosystem changes. In some areas the introduced non-native White Sucker, Catostomus commersonii, with which they hybridize, and the Yaqui Sucker, Catostomus bernardini, have been able to out compete the Rio Grande Sucker causing their extirpateration and they have been eliminated. They are currently a major rehabilitation subject in the Southwestern United States with strong efforts trying to reestablish populations to native area. They are small in stature and are of limited interest to most.