The channel catfish (Ictalurus punctatus) is North America's most numerous catfish species. It is the official fish of Kansas, Missouri, Nebraska, and Tennessee, and is informally referred to as a "channel cat". In the United States, they are the most fished catfish species with around 8 million anglers targeting them per year. They also have very few teeth and swallow food whole. The popularity of channel catfish for food has contributed to the rapid expansion of aquaculture of this species in the United States. It has also been widely introduced in Europe, Asia and South America, and it is legally considered an invasive species in many countries.
Channel catfish possess very keen senses of smell and taste. At the pits of their nostrils (nares) are very sensitive odor-sensing organs with a very high concentration of olfactory receptors. In channel catfish, these organs are sensitive enough to detect several amino acids at about one part per 100 million in water. In addition, the channel catfish has taste buds distributed over the surface of its entire body. These buds are especially concentrated on the fish's four pair of barbels (whiskers) surrounding the mouth — about 25 buds per square millimeter. This combination of exceptional senses of taste and smell allows the channel catfish to find food in dark, stained, or muddy water with relative ease. They also possess a Weberian apparatus, which amplifies sound waves that would otherwise not be perceivable. The barbels of channel catfish have been falsely thought to sting on contact. They do not; however, these catfish do have spines on their pectoral and dorsal fins that, if not handled carefully, can cause injury.
Channel catfish are native to the Nearctic, being well distributed in lower Canada and the eastern and northern United States, as well as parts of northern Mexico. They have also been introduced into some waters of landlocked Europe (Czech Republic and Romania) and parts of Malaysia and almost as many parts of Indonesia. They thrive in small and large rivers, reservoirs, natural lakes, and ponds. Channel "cats" are cavity nesters, meaning they lay their eggs in crevices, hollows, or debris, to protect them from swift currents. In Canada, the species is largely, though not exclusively, limited to the Great Lakes watershed from Lake Nipigon southward.
The channel catfish is adapted to limited light conditions. Members of the genus Ictalurus, which inhabit muddy waters, do not depend solely on visual cues. Instead, they are known to rely heavily on chemotactic cues. Sound production may be another important means of communication among channel catfish and other species living in turbid habitats.
The North American channel catfish is an ostariophysan, or a bony fish occupying a freshwater habitat. These fishes are known to produce club cells and alarm substances for communication purposes. Both the fish's habitat and the presence of chemosensory cells covering the body are presumably the results of favored selection for this method of communication. Catfishes are capable of producing and recognizing individual specific pheromones. Through these pheromones, a catfish can identify not only the species and sex of a conspecific, but also its age, size, reproductive state, or hierarchical social status.
Territoriality in channel catfish is identifiable by a change in body odor, which is recognizable by other members of the same species. This chemical change in the amino-acid composition of the skin mucus can be noted by chromatographic methods, and are not long-lasting; rather, they last only long enough to communicate to other fish in the vicinity. Changes may be the result of the release of the contents of the club cells. These cells do not open directly to the surface of the skin, but injury caused by fighting and other agonistic behaviors may release the cells’ contents. Since catfish have a dominance hierarchy system, information relative to the change of status of any fish is important in recognition of the social strata.
Catfish have enhanced capabilities of taste perception, hence called the “swimming tongue”, due to the presence of taste buds all over the external body surface and inside the oropharyngeal cavity. Specifically, they have high sensitivity to amino acids, which explains their unique communication methods as follows. The catfish has a facial taste system that is extremely responsive to L-alanine and L-arginine. More specifically, their facial taste system senses heightened levels of L-amino acids in freshwater. Feeding behavior to food is due to amino acids released by food. This is reported to cause maxillary and mandibular barbel movements, which orient the catfish's posture and food search. When the food stimulates the taste receptors, it causes more excitation which is seen in exaggerated biting, turning, or mastication.
Adult channel catfish, over 45 cm (17.7 in), consume fishes such as yellow perch and sunfish. The diet of adults consists of snails, clams, crustaceans (such as crayfish), snakes, frogs, small fish, insects, aquatic plants, algae, seeds, grains, nuts, and even small birds and small mammals occasionally. Younger channel catfish are more consistently omnivorous, eating a large variety of plants and animals.
