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Hypostomus plecostomus, Pterygoplichthys spp.

Armored Catfishes

Synonym(s): Suckermouth Catfish, Algae Eaters
Class: Actinopterygii
Order: Osteichthyes
Family: Loricariidae

Photographer: United States Geological Survey
Source: United States Geological Survey


The armored catfishes (Family: Loricariidae. Also known as plecos or algae-eaters) feed on algae (algivorous), are mostly nocturnal, and have a noticeable sucker located on the underside (ventral surface) of the head. Loricariids can range in size from 3 inches to over three feet in adequate conditions. Their flattened ventral surface allows the fish to use their suckers on most substrates. The adipose fin, which is the fin located between the dorsal fin and the tail, has a spine, and pectoral fins have thick, toothed spines that are used in male-male competition and locomotion.

There are several species of loricariids now established in Texas. These include Hypostomus plecostomus (Common Pleco) and several Pterygoplichthys species: P. anisitsi (Paraná Sailfin Catfish), P. disjunctivis (Vermiculated Sailfin Catfish) and P. multiradiatus (Orinoco Sailfin Catfish), although there are more records of P. anisitsi. They are easily confused with one another because the black-lined patterns on these fish species can vary significantly and resemble one another.

Ecological Threat: With the over-abundance of loricariids in freshwater ecosystems, local indigenous species can be out-competed and reduced. This could lead to a collapse of freshwater fisheries in addition to the obvious ecological dangers. While the loricariids were introduced to control algae populations, it is unknown how effective these fish are at controlling them. These species also dig burrows in banks, which can cause erosion and bank destabilization.

Biology: Loricariids are cavity builders, digging burrows into banks, and can lay more than 300 eggs in their nests. Males guard the nest and the eggs hatch within 4 to 20 days depending on the species. In addition to their successful breeding strategies, loricariids are hearty fish that can withstand a wide range of ecological conditions. In fact, the fish can gulp air and survive out of water for a day or more. Fishes in the genus Pterygoplichthys have been found to survive salinities up to 10ppt, allowing them to invade brackish habitats as well.

History: Loricariids are native to tropical South America, Panama, and Costa Rica. However, their range is increasing due to intentional human and accidental introductions throughout the world. Loricariids are frequently released into freshwater bodies in the United States and throughout the world by natural resource managers to remove algae and control aquatic plants and are found in numerous states in the U.S. However, their effectiveness in controlling algal and plant growth in natural systems is undocumented.

Plecos are common in the aquarium trade, and aquarium dumping is a primary introduction pathway in the United States.

U.S. Habitat: In the U.S., loricariids are found primarily in freshwater habitats such as rivers, bayous, and canals but may also inhabit brackish waters.


Native Origin: Central and South America. Loricariids can be found in most freshwater habitats in tropical Costa Rica, Panama, and South America, but many species have small natural ranges. They can also be found in some brackish water habitats.

U.S. Present: FL, NV, TX, and possibly WI.

Distribution in Texas: Reproducing populations of loricariids occur in spring-influenced habitats of the San Antonio River (Bexar County), Comal Springs (Comal County), San Marcos River (Hays County), and San Felipe Creek (Val Verde County) as well as in the bayou and canal systems in the Houston area.

Hypostomus plecostomus was found in the headwaters of the San Antonio River in 1962, after individuals escaped the San Antonio Zoo. It and has maintained an obvious presence with a stable population since 1990. This species is also now found in the San Marcos and Comal rivers.

Pterygoplichthys anisitsi has been found in the Buffalo and Brays Bayous systems in Houston, TX since 2001 and there are numerous other records in the Houston area. As of 2016, survey efforts have shown reproductive populations are being maintained in these bayou systems.

Pterigoplichthys disjunctivis has also been found in the San Antonio River and there are isolated records of P. multiradiatus in the San Antonio River and the Houston area.

Because all of these species have been found in isolated cases around the state, and because aquarium owners may dump their aquarium anywhere in the state, it is important for Texans to remain vigilant and to report sightings of these fish to TPWD.


Superficially resemble catfish, but lacking the barbels (tentacle-like projections growing from the mouth) that are so characteristic of catfish. In addition, unlike catfish, the armored catfish have scaly skin and dark spots/lines on their bodies.


Management often focuses on the aquarium trade and advising owners to avoid releasing loricariids is paramount in curbing the invasion. By being a responsible pet owner you can prevent the spread of these pests in our Texas freshwater systems. Follow this link to learn about alternatives to dumping your tank when you no longer want your aquarium pets.

Biologists working in Harris County started aggressive fishing strategies in Buffalo and Brays Bayous in 2016 but the current status of these efforts is unknown (2020). There have also been control efforts in the San Marcos and Comal rivers under the Edwards Aquifer Habitat Conservation Plan.

Text References

Podkowa, Dagmara, and Lucyna Goniakowska-Witalińska. "Morphology of the air-breathing stomach of the catfish Hypostomus plecostomus." Journal of Morphology. 257.2 (2003): 147–163.

Power, Mary. "Resource Enhancement by Indirect Effects of Grazers: Armored Catfish, Algae, and Sediment." Ecology. 71.3 (1990): 897-904.

Shafland, P. L. "The Continuing Problem of Non-Native Fishes in Florida." Fisheries. 1.6 (1976): 25

Dan Foley, PhD. - Sul Ross State University - Rio Grande College -
Krista Capps -

Online References

SEARCh Online

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Last Updated: 2020-08-18 by Monica McGarrity, TPWD. (Original: Amber Bartelt - Sam Houston State University)