Catfish is a common name for about 2200 species of fishes, out of which about 1200 are South American. Among them, two families are primarily marine and rest are fresh water. Catfishes are mostly nocturnal scavengers, living near the bottom in swallow waters.

The name catfish is derived from the feelers, or barbels, that extend from each side of the upper jaw of the fish and, in some species, from the lower jaw also, suggesting the whiskers of a cat. The dorsal and pectoral fins are often edged with sharp spines, in some cases poisonous ,that are used in defense and can inflict severe wounds.Members of several catfish families in South America are covered with bony plates. A European species, the sheatfish, or wels, is the largest catfish, reportedly reaching a weight of 290 kg and a length of almost 4m.

The blind catfish, found in caverns in eastern Pennsylvania, has atrophied eyes, and the electric catfish of the Nile River and tropical central Africa is capable of giving an electric shock.Another odd catfish, the so-called walking catfish, originally occurred in eastern India and Southeast Asia. In 1968, it was discovered near Boca Raton, Florida, following its import by tropical-fish dealers. Its maximum length is 56cm. In "walking" to areas of deeper water in dry spells, this catfish moves across land by a slithering motion combined with a thrashing of its tail. In addition, a stout spine in each pectoral fin digs into the ground to help balance and propel the fish. It is able to breathe air by means of a modified gill arch that forms an air chamber.

Of the numerous species of North American catfishes, the bullhead is commonly fished for eating . Of greatest commercial importance are fishes in the Mississippi river valley and the Gulf states, some of which weigh as much as 70kg. The blue catfish, or chuckle head, and the canned catfish , the flesh of which is esteemed as equal to that of black bass, form the major part of the harvest.