[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.

[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.