Catfish (order Siluriformes) are a diverse group of fish. Notable for their prominent barbels, they are found in freshwater environments of all kinds, with species on every continent except Antarctica. Some species from the families Ariidae and Plotosidae are also found in marine environs. They range in size and behavior from the largest freshwater fish in the world (the European wels, or Silurus glanis), to detritivores (species that eat dead material on the bottom), and even to a tiny parasitic species commonly called the candiru (Vandellia cirrhosa). At present there are 35 catfish families, although this number is in constant flux due to taxonomic work on the order.
Catfish have no scales. All catfish, except members of Malapteruridae (electric catfish), possess a strong, hollow, bonified leading ray on their dorsal and pectoral fins, through which a stinging protein can be delivered if the fish is irritated. In members of the family Plotosidae, and of the genus Heteropneustes, this protein is so strong it may hospitalize humans unfortunate enough to receive a sting.
Catfish are important food fish throughout the world. Ictalurids are cultivated in North America (especially in the Deep South), while Clariids and Pangasiids are heavily cultured in Africa and Asia. There is also a large and growing ornamental fish trade, with catfish a popular component of many aquaria.
Examples of catfish species: