Catfish - biology.

Catfish - biology. Catfish, common name for a group of more than 2,500 species of fish, classified in about 30 families and found worldwide. Catfish are mostly nocturnal scavengers, living near the bottom in shallow waters. Two families are primarily marine, and all other families inhabit fresh water. Catfish are named for the feelers, or barbels, located around the mouth suggesting the whiskers of a cat. These feelers are used for finding food. The body is scaleless, either naked or with bony plates. The dorsal and pectoral fins are often edged with sharp spines that are used for defense. They can inflict severe wounds and are poisonous in some species. Catfish range in size from about 32 mm (1.25 in) and 7 g (0.25 oz) to 4.5 m (15 ft) and 320 kg (700 lb). The huge sheatfish native to Europe can weigh up to 180 kg (up to 400 lb). Smaller species include stone cats and mad toms, which build nests in the mud or under stones and guard the eggs and young. In many of the marine catfish of the Ariidae family, the pea-sized eggs are carried and cared for in the mouth of the male until hatched. The blind catfish, found in caverns in eastern Pennsylvania, has atrophied eyes. The electric catfish of the Nile and tropical central Africa is capable of giving an electric shock with enough voltage to stun an animal (350 to 450 volts) (see Electric Fish). Some catfish of the family Mochokidae normally swim upside down. The walking catfish can travel across land to areas of deeper water during dry spells. On land, it moves using a slithering motion combined with a thrashing of its tail. 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 that forms an air chamber. This catfish originally occurred in eastern India and Southeast Asia but was discovered near Boca Raton, Florida in 1968, following its importation by tropical-fish dealers. Its maximum length is 56 cm (22 in). Of the numerous catfish species native to North America, the bullhead is commonly fished for eating. Of greatest commercial importance are fish in the Mississippi River valley and the Gulf states, some of which weigh as much as 70 kg (150 lb). The blue catfish, or chucklehead, and the channel catfish, the flesh of which is esteemed as equal to that of black bass, form the major part of the harvest. Many species of catfish have been listed as endangered on the International Union for the Conservation of Nature and Natural Resources (IUCN) Red List of Threatened Species. These include the giant catfish, the cave catfish, and the Andean catfish. Scientific classification: Catfish make up the order Siluriformes. The sheatfish is classified as Silurus glanis. Stone cats belong to the genus Noturus and mad toms to the genus Schilbeodes. The blind catfish is classified as Gronias nigrilabris, the electric catfish as Malapterurus electricus, and the walking catfish as Clarias batrachus. Bullheads belong to the family Ictaluridae. The blue catfish is classified as Ictalurus furcatus, the channel catfish as Ictalurus punctatus, the giant catfish as Pangasius gigas, the cave catfish as Clarias cavernicola, and the Andean catfish as Astroblepus ubidiai. The two marine families are Ariidae and Plotosidae. Contributed By: Kenneth A. Chambers Microsoft ® Encarta ® 2009. © 1993-2008 Microsoft Corporation. All rights reserved.