Clarias

Clarias is 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 Asia Minor and in Africa.^[5] The diversity of these catfishes is highest in Africa.^[6] Some (notably the walking catfish) have become pest species where they were accidentally introduced, 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. Many species 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:

African species

Clarias agboyiensis Sydenham, 1980 Clarias albopunctatus Nichols & La Monte, 1953 Clarias alluaudi Boulenger, 1906 (Alluaud's catfish) Clarias angolensis Steindachner, 1866 Clarias anguillaris Linnaeus, 1758 (mudfish) Clarias buettikoferi Steindachner, 1894 Clarias buthupogon Sauvage, 1879 Clarias camerunensis Lönnberg, 1895 Clarias cavernicola Trewavas, 1936 (cave catfish) Clarias dhonti Boulenger, 1920 Clarias dumerilii Steindachner, 1866 Clarias ebriensis Pellegrin, 1920 Clarias engelseni Johnsen, 1926 Clarias gabonensis Günther, 1867 Clarias gariepinus Burchell, 1822 (North African catfish) Clarias hilli Fowler, 1936 Clarias jaensis Boulenger, 1909

Clarias laeviceps T. N. Gill, 1862 Clarias laeviceps dialonensis Daget, 1962 Clarias laeviceps laeviceps T. N. Gill, 1862 Clarias lamottei (?) Daget & Planquette, 1967 [8] Clarias liocephalus Boulenger, 1898 (smoothhead catfish) Clarias longior Boulenger, 1907 Clarias maclareni Trewavas, 1962 Clarias macromystax Günther, 1864 Clarias monsembulai Bernt and Stiassny, 2022 [9] Clarias ngamensis Castelnau, 1861 (blunt-toothed African catfish) Clarias nigromarmoratus Poll, 1967 Clarias pachynema Boulenger, 1903 Clarias platycephalus Boulenger, 1902 Clarias salae Hubrecht, 1881 Clarias stappersii Boulenger, 1915 (blotched catfish) Clarias submarginatus W. K. H. Peters, 1882 Clarias theodorae M. C. W. Weber, 1897 (snake catfish) Clarias werneri Boulenger, 1906 (Werner's catfish)

Asian species

Clarias abbreviatus Valenciennes, 1840 Clarias anfractus H. H. Ng, 1999 [10] Clarias batrachus Linnaeus, 1758 (Walking catfish) Clarias batu K. K. P. Lim & H. H. Ng, 1999 [5] Clarias brachysoma Günther, 1864 Clarias cataractus Fowler, 1939 Clarias dayi Hora, 1936 Clarias dussumieri Valenciennes, 1840 Clarias fuscus Lacépède, 1803 (Hong Kong catfish) Clarias gracilentus H. H. Ng, K. H. Dang & V. T. Nguyen, 2011 [11] Clarias insolitus H. H. Ng, 2003 [3] Clarias intermedius Teugels, Sudarto & Pouyaud, 2001 [6] Clarias kapuasensis Sudarto, Teugels & Pouyaud, 2003 [12] Clarias leiacanthus Bleeker, 1851 Clarias macrocephalus Günther, 1864 (bighead catfish) Clarias magur F. Hamilton, 1822 Clarias meladerma Bleeker, 1846 (blackskin catfish) Clarias microspilus H. H. Ng & Hadiaty, 2011[13] Clarias microstomus H. H. Ng, 2001 [4] Clarias nebulosus Deraniyagala, 1958 Clarias nieuhofii Valenciennes, 1840 (slender walking catfish) Clarias nigricans H. H. Ng, 2003 [14] Clarias olivaceus Fowler, 1904 Clarias planiceps H. H. Ng, 1999 [10] Clarias pseudoleiacanthus Sudarto, Teugels & Pouyaud, 2003 [12] Clarias pseudonieuhofii Sudarto, Teugels & Pouyaud, 2004 [7] Clarias serniosus H. H. Ng & Kottelat, 2014 [15] Clarias sulcatus H. H. Ng, 2004

Fossil species

• †Clarias falconeri Lydekker, 1886, from India

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

Clarias catfish and primarily Clarias batrachus (walking catfish) have been introduced to many different areas of the world, causing problems for native wildlife. The effect of the 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, the UK^{[citation needed]}, Papua New Guinea, Guam, Taiwan, Thailand, and Cuba.