catfish, common name applied to members of the fish families constituting the order Siluriformes, found in fresh and coastal waters. Catfish are named for the barbels (
) around their mouths and have scaleless skins, fleshy, rayless posterior fins, and sharp defensive spines in the shoulder and dorsal fins. They are able to use the swim bladder to produce sounds, and have a complex set of bones forming a sensitive hearing apparatus. Some species, such as the stone and tadpole catfishes and the madtom, can inflict stings by means of poison glands in the pectoral spines. Catfish are usually dull-colored, though the madtoms of E North American streams are brightly patterned. Members of most madtom species are no more than 5 in. (12.7 cm) long; some are less than 2 in. (5 cm) long. Danube catfish called wels, or sheatfish, reach a length of 13 ft (4 m) and a weight of 400 lb (180 kg), and the Mekong giant catfish can reach 10 ft (3 m) and 550 lb (250 kg). Catfish are omnivorous feeders and are valuable scavengers.
Types of Catfish
The South American catfishes show great diversity: There are small, delicate species armored with bony plates; parasitic types that live in the gills of other fish; and one catfish of the E Andes in which the pelvic fins are modified into suckers that enable it to cling to rocks. African species include the electric fish and the Nile catfish, which swims upside down to feed at the water's surface and has a white back and a dark belly, the reverse of the normal coloration.
Of the 30 American species the largest and most important is the blue, or Mississippi, catfish, an excellent food fish weighing up to 150 lb (70 kg). Best known is the smaller channel catfish, which reaches 20 lb (9 kg) and has a deeply forked tail and slender body. The stonecat, 10 in. (25.4 cm) long, is found in clear water under logs and stones. The bullheads, or horned pouts, are catfish of muddy ponds and streams, feeding on bottom plants and animals. Bullheads have square or slightly rounded tails and may reach 1 ft (30 cm) in length and 2 lb (0.9 kg) in weight. The black, yellow, and brown bullhead species are common in the waters of the central and eastern states.
There are no catfish in the Pacific except the introduced white catfish. Marine catfish found during the summer in bays and harbors of the Atlantic and Gulf states include the 2-ft (61-cm) gaff-topsail catfish, named for its long, ribbonlike pectoral and dorsal fins, and the smaller sea catfish, a very common trash fish. The males of both these species carry the fertilized eggs in their mouths (and therefore do not eat) until well after the young hatch, a period of two months. In certain other species the eggs are embedded in the underside of the female. Some tropical catfish survive dry seasons by burrowing into the mud or by crawling overland in search of water.
Catfishes are classified in the phylum Chordata, subphylum Vertebrata, class Actinopterygii, order Siluriformes.