Introductioncatfish, common name applied to members of the freshwater fish families constituting the suborder Nematognathi. The catfish is related to the sucker and the minnow, and like them has a complex set of bones forming a sensitive hearing apparatus. Catfish are named for the barbels ("whiskers") 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. 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.
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