• Catfish features....
  • Catfish are either naked (scaleless) or covered in bony scutes (armour). No catfish have scales in the true sense of what a fish scale is.
• Catfish are generally classified depending on:
  • whether or not they have an adipose fin - 22 of the families of catfish have an adipose fin.
  • the number of barbels they have - catfish with a full complement of barbels have 8 barbels (4 pairs) with 2 pairs on the upper jaw and 2 pairs on the lower jaw.
  • the shape of their dorsal, pectoral and caudal fins - some catfish have no dorsal fin (eg. Electric Catfish). In others, such as the Eel-tail Catfish (right - Rendahl's Catfish) the posterior dorsal fin, caudal fin and anal fin all join together.
  • pectoral and dorsal spines
  • the structure of the Weberian Apparatus, which consists of four small bones connected with the inner ear.
  • the shape and position of the swim bladder, one of the most important organs of the catfish, and
  • the relative proportions of each part of the body, such as the size of the head in relation to the total length of the fish.

• Many species in several families have venomous defensive spines on their dorsal and/or pectoral fins. While they won't necessarily kill a person, they will inflict a very painful wound.
• Unlike most freshwater fish, many catfish are nocturnal and depend mainly on senses other than sight, such as tactile and chemosensitive barbels, or enlarged olfactory organs. This means that catfish are preadapted for life in caves, aquifers, and deep river channels where light is poor.
• Some species of catfish have some very unusual features. For instance:

• Some catfish have the ability to breathe atmospheric air and one group, Clariid catfish (Genus Clarias), take this ability to extremes, regularly leaving the water and walking over land to a new waterhole.
• These catfish have air-breathing organs that enable them to live out of water.
• The blind catfish is unusual in that it lives in caves. Because eyesight is of no use in a cave, their eyes have become atrophied and useless.
  
• The candiru of South America is the only vertebrate known to parasitise humans. This catfish uses spines located around its head to lodge itself in the human urethra.
• A painful operation is required to remove the fish. The candiru is more feared by the native Indians than the Pirahna.
• Species in the genus Malapterurus (Electric Catfish) are capable of generating charges of 400 volts or more.
  
• Several groups of catfish communicate acoustically; some by vibrating the swim bladder, others by rattling their fin spines.

• Where are catfish found?
  • Catfish are found in fresh and marine waters of every continent and catfish fossils have been found in Antarctica.
  • However, they are most diverse in species and morphology in tropical South America, Africa and Asia.
  • The earliest known fossil siluriforms are in freshwater and marine deposits of late Cretaceous (Campanian and Maastrichtian) age.
  • Many catfish around the world have huge economic value and are fished for human consumption, the aquarium trade, or recreational fishing. For example:
    • The North American channel catfish (Ictalurus punctatus) supports a $450 million/yr aquaculture industry.
      
    • The South American, armored corydoras and plecostomus catfish are true icons in the aquarium trade.
      
    • Several catfish (such as the monster Goliath catfish in South America) are actively sought by big game fishermen.
  • Catfish are also represented in stories and legends in some of their native habitats. Most of the stories involve them growing to gigantic proportions - large enough to eat small children. One, the Red-tailed Catfish of South America, certainly grows to a very large size and has been implicated in such activities.
  • The flip side to this is that translocated species cause substantial economic loss and damage to natural ecosystems and native fish stocks.
  • In Queensland, several catfish genera are declared noxious under legislaton (eg Walking Catfish - Clarias sp; Tiger Shovelnose - Pseudoplatystoma fasciatum (right) and Parasitic Catfish - all members of the families Trichomycteridae and Vandelliinae).
• Feeding....
  • Most catfish are omnivores, but some have highly specialised diets.
  • Some, such as the Suckermouth Catfish require wood in their diet. Many of these catfish are also very effective at removing algae form the tank.
  • Catfish should not be treated as "just scavengers" in the aquarium as, while they will eat uneaten food in the tank, scavenging is often not enough to keep them in good health - many catfish should be fed specifically to ensure they get enough food and their health is maintained.
• Breeding....
  • Catfish are egg-layers and use a variety of methods when breeding.
  • Most species of catfish provide some parental care to eggs and some species also care for their fry.
    • Hoplo Catfish (Megalechis personata) and other members of the Callichthid Family of catfish, such as Dianema species build a bubble nest on the surface of the water. The eggs are placed into the nest and the male guards the eggs and fry as they hatch.
    • Male Suckermouth Catfish, such as Bristlenose (Ancistrus dolichopterus), Sailfin Pleco (Glyptoperichthys gibbiceps) and Zebra Peckoltia (Hypancistrus zebra) guard eggs in caves that may be tunnels excavated into the mud of river banks or under overhanging rocks and wood.
  • There is an interesting symbiotic relationship between certain African bagrids that protect the fry of cichlids.
  • One of the most unusual breeding rituals is that of the Cuckoo Catfish (Synodontis multipunctatus).
    • This catfish from Lake Tanganyika works in the same way the Cuckoo bird lays its eggs in the nests of other birds.
  • The catfish breeds with mouthbrooding cichlids. The catfish swim between a spawnining cichlid pair and lay and fertilise their eggs.
  • The catfish eggs are picked up with the cichlid eggs by the female cichlid, where they are brooded in her mouth.
  • The baby catfish hatch earlier than the cichlid eggs and eat the cichlid eggs.
  • Members of the Family Ariidae (Salmontail Catfish) are mouth brooders, with the male brooding the eggs.

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