Catfish

Catfish make up the order Siluriformes, one of the most diverse groups of fish with well over 3,000 described species found on every continent except Antarctica. They are unified by scaleless, often slimy skin and prominent barbels around the mouth that resemble whiskers, giving the group its name. Body size varies enormously across the order, from tiny inch-long species to the giant Mekong catfish, which can exceed 2.5 meters. The channel catfish, native to much of North America and now widely introduced elsewhere, is one of the most recognizable and widespread members of the group and a popular sport fish.

Catfish as a group are identified by a consistent set of features despite huge diversity in size and shape.

• Skin: scaleless, often coated in protective mucus
• Barbels: typically four pairs around the mouth, used to taste and smell for food
• Fins: sharp, sometimes venomous, spines at the leading edge of the dorsal and pectoral fins; small fleshy adipose fin present in many species
• Head: broad and flattened
• Channel catfish specifically: olive-gray to bluish body with scattered dark spots, deeply forked tail, size 30-130 cm

Coloration and body proportions vary widely between species within the order.

Catfish occupy freshwater rivers, lakes, reservoirs, and swamps worldwide, with some species also found in brackish estuaries. Most are bottom-oriented, favoring areas with cover such as submerged logs, undercut banks, or mud substrates, and many tolerate warm, turbid, low-oxygen water better than most other freshwater fish. Channel catfish specifically are native to large parts of the Mississippi River drainage and other North American watersheds but have been introduced to reservoirs and rivers on other continents. As a group, catfish are found from Arctic-adjacent rivers to tropical lakes, reflecting the order's exceptional ecological range.

Catfish are predominantly nocturnal, using their barbels, which are covered in taste buds, to locate food by smell and taste in murky or dark water where vision is less useful. Diet is typically omnivorous to carnivorous, including insects, crustaceans, smaller fish, and plant material, depending on the species. Most catfish are solitary or loosely aggregated rather than tightly schooling, though some smaller species do form groups. Many species practice nest guarding, with a parent, often the male, defending a cavity or depression containing eggs and fry until they disperse. Some catfish species can tolerate brief periods out of water and survive in low-oxygen conditions by gulping air, an adaptation to seasonal drying habitats.