Catfish is divers group of fish that contains a wide variety of different species. You will find more specific articles regarding the common aquarium species further down on this page. Scrolling down is also a good idea if you are looking for more specified information regarding Catfish husbandry, Catfish breeding etcetera.
All Catfish species belong to the Order Siluriformes. There are currently 37 known Catfish families. The 37th Catfish family, the Lacantuniidae, was named as late as June 2005. The name of the family is derived from the Lacantun River in Chiapas, a region in south Mexico. The new species in the Family Lacantuniidae was found in the Lacantun River. As the knowledge about the Catfish species grows there is a constant fluctuation in the taxonomy. The new DNA techniques have also made it possible to categorise fish species more correctly, and the Order Siluriformes is not the only order of fish that have gone through large changes during the last few years.
Catfish species live in freshwater and are found on every continent except for Antarctica. There are also a few Catfish species that live in saltwater; species from the Family Plotosidae and Ariidae. The Catfish can be recognized on its well-known and prominent barbells. The barbells are elongated tactile organs located close to the mouth; quite similar to the whiskers on a cat. Just like the cat's whiskers, the barbells are used to screen the environment and heighten the animal's awareness of its surroundings. The barbells are equipped with taste buds and the Catfish use the barbells when catching fish in dark and cloudy waters where the visibility is low. The Catfish species are not the only one with barbells; barbells are also found on several carps, the goatfish and a few shark species.
One thing that all known Catfish species have in common is the lack of scales. Another shared characteristic is the hollow leading ray on the dorsal and pectoral fins. This leading ray is very strong and the Catfish can use it to excrete a potent protein when the Catfish become frightened or annoyed. This protein will sting a lot, and Catfish species of the Family Plotosidae and the Genus Heteropneustes have a protein that is strong enough to injure a human. A person that has received a sting from one of these species can require hospital care. Catfish from the Family Malapteruridae distinguish themselves from all the other Catfish species since they are without this hollow leading ray and incapable of protein attacks. Malapteruridae species are instead capable of sending out a severe electric shock of up to 350 volts. All the different species in the Family Malapteruridae are commonly known as Electric Catfish.
The Catfish group is very diverse and many species are unsuitable in aquariums. The longest species is the Wells Catfish (Silurus glanis) that can reach of size of five meters. The heaviest Catfish species is the Giant Mekong Catfish (Pangasius gigas) that lives in Southeast Asia. In 2005, a Giant Mekong Catfish weighing 293 kg was caught in Thailand. Other species are hard to keep in aquariums not because of their size, but due to the fact that they have requirements that are hard to satisfy in captivity. The Candirú Catfish (Vandellia cirrhosa) will for instance require other fishes that they can feed from since they are parasites. In the wild, Candirú Catfish affix them selves to the gill cavities of larger fishes and draw blood from the gills. The Candirú Catfish is sometimes nicknamed “The Vampire Fish of Brazil”. It can unfortunately also attach it self to bathing humans and is attracted by blood and urine.