Clarias is a genus of catfishes (order Siluriformes) of the family Clariidae, the airbreathing catfishes. The name is derived from the Greek chlaros, which means lively, in reference to the ability of the fish to live for a long time out of water.^[1]

Quick Facts Clarias Temporal range: Lower Pliocene - recent, Scientific classification ...

Clarias Temporal range: Lower Pliocene - recent
Walking catfish, Clarias batrachus
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Actinopterygii
Order:	Siluriformes
Family:	Clariidae
Genus:	Clarias Scopoli, 1777
Type species
Silurus anguillaris Linnaeus, 1758
Species
Many, see text.
Synonyms
Chlarias Scopoli, 1777 Macropteronotus La Cepède, 1803 Clarias Cuvier, 1816 Cossyphus M’Clelland, 1844 Phagorus M’Clelland, 1844 Dinotopteroides Fowler, 1930 Prophagorus Smith, 1939 Anguilloclarias Teugels, 1982 Brevicephaloides Teugels, 1982 Clarioides Teugels, 1982 Platycephaloides Teugels, 1982

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Clarias has been found to be paraphyletic. A species of Heterobranchus (H. longifilis) clusters deeply inside the Clarias group.^[2]

They are found in inland waters throughout much of the Old World, and are one of the most widespread catfish genera in the world.^[3][4] The genus is found in Southeast Asia and East Asia westwards through India and the Asia Minor to Africa.^[5] The diversity of these catfishes is highest in Africa.^[6] Some (notably the walking catfish) have become pest species where they have been accidentally introduced, and particularly in Cuba, where their introduction was intentional.

Clarias species are recognized by their long-based dorsal and anal fins, which give them a rather eel-like appearance. These fish have slender bodies, a flat, bony head, and a broad, terminal mouth with four pairs of barbels. They also have a large, accessory breathing organ composed of modified gill arches.^[3][5] Also, only the pectoral fins have spines.^[7]

There are currently 62 species recognized in this genus:

Many of the species are of great economic importance in both fisheries and fish culture.^[6]

Clarias catfish and primarily Clarias batrachus (walking catfish) have been introduced to many different areas of the world, where they are causing problems for the native wildlife. The effect of introduction of these fish varies from area to area, but as they are predatory, they often affect the local wildlife by eating other fish, birds, and amphibians. In Florida, the fish are causing problems by invading aquaculture farms and preying on the fish cultivated there.^[16] Countries where one or several Clarias species have been introduced include Indonesia, the United States, Hong Kong, China, UK, Papua New Guinea, Guam, Taiwan, Thailand, and Cuba.