Members of the catfish family Ictaluridae range from very small to very large fish, do not have scales, and possess eight sensory barbels, or "whiskers", around their mouth - four on the chin, two on the snout, and one on each corner of the mouth. They have three median fins: anal, adipose, and dorsal. The anal fin has a long base and is located on the underside of the fish. The dorsal fin is located on the back and has a single sharp spine in the front part. The adipose fin is a small, fatty fin situated between the dorsal fin and the tail. Two sets of paired fins, the pelvic and pectoral fins, are also present. Both pectoral fins have a single spine along the front section of the fin, and the madtoms have poison glands associated with these spines that are capable of inflicting a painful, but not dangerous, wound.
Members of the catfish family in the U. S. were originally distributed in most states east of the Rocky Mountains, but various species have been widely introduced into western states where they did not occur naturally. Mature individuals among the species range in size from several pounds for the channel catfish to only a few ounces for the tiny madtoms.
Catfishes are generally warmwater fish that are more tolerant of water with low oxygen and low light levels than many other groups of fishes. They are often nocturnal or feed during the day in turbid waters, using their sensory barbels to feed upon insects, crustacea and fish.
Channel catfish are the most common farm-raised fish in the United States, primarily in the southern U.S. Although bullheads and the larger species of catfish are commonly caught by anglers, madtoms and related small members of this family are seldom observed. After hatching in late spring, adult bullheads protect schooling young for as long as two weeks after hatching, during which time compact schools of small bullheads may be observed close to shore.