Group

Catfish

About Catfish

Catfish are a diverse group of ray-finned fish of the order Siluriformes (historically Nematognathi). Catfish are named for their prominent barbels, which resemble a cat's whiskers, though not all catfish have prominent barbels. All Siluriformes lack scales, instead possessing either smooth skin or armour-plated bodies. This order of fish are defined by features of the skull (such as maxillae modified into the barbels' bases) and swimbladder. Catfish range in size and behavior from the three largest species alive, the Mekong giant catfish from Southeast Asia, the wels catfish of Eurasia, and the piraíba of South America, to detritivorous and scavenging bottom feeders, down to the tiny ectoparasitic species known as the candiru.

In the Southern United States, catfish may be known by a variety of slang names, such as "mud cat", "polliwogs", or "chuckleheads". Such names are regional and unstandardized. For instance, "chucklehead" in one region may refer to a bullhead catfish but indicate blue catfish elsewhere.

Catfish as a group are of considerable commercial importance; many of the larger species are farmed or fished for food, such as the Pangasius (a shark catfish) and Clarias (like the walking catfish). Many of the smaller species, such as members of the genus Corydoras, are important in the aquarium hobby. Some species, such as plecos of the genus Pterygoplichthys, are prolific invasives due to the aquarium hobby.

Appearance

Most catfish are bottom feeders. In general, they are negatively buoyant, which means that they usually sink rather than float due to a reduced gas bladder and a heavy, bony head. Catfish have a variety of body shapes, though most have a cylindrical body with a flattened ventrum to allow for benthic feeding. A flattened head allows for digging through the substrate, as well as perhaps serving as a hydrofoil. Some have a mouth that can expand to a large size and contains no incisiform teeth; catfish generally feed through suction or gulping rather than biting and cutting prey. Some families, though, notably the Loricariidae and Astroblepidae, have a suckermouth that allows them to fasten themselves to objects in fast-moving water.

Habitat

Catfish live inland or in coastal waters of every continent except Antarctica. Catfish have inhabited all continents at one time or another. They are most diverse in tropical South America, Asia, and Africa, with one family native to North America and one family in Europe. More than half of all catfish species live in the Americas. They are the only ostariophysans that have entered freshwater habitats in Madagascar, Australia, and New Guinea.

Behaviour

Many catfish are nocturnal, but others (many Auchenipteridae) are crepuscular or diurnal (most Loricariidae or Callichthyidae, for example).

Humans & conservation

Catfish are easy to farm in warm climates and are often sold cheaply by local grocers. About 60% of U.S. farm-raised catfish are grown within a 65-mile (100-km) radius of Belzoni, Mississippi. Channel catfish (Ictalurus punctatus) support a $450 million/yr aquaculture industry. The largest producers are located in the Southern United States, including Mississippi, Alabama, and Arkansas.

Catfish raised in inland tanks or channels are usually considered safe for the environment, since their waste and disease should be contained and not spread to the wild.