• Bosnian: som
• Bulgarian: сом
• Croatian: som
• Czech: sumec
• Dutch: meerval
• Finnish: monni
• French: poisson-chat, silure
• German: Wels
• Greek: γατόψαρο (gatopsaro)
• Hungarian: harcsa
• Isthmus Zapotec: guluxu
• Italian: pesce gatto
• Japanese: 鯰
• Korean: 메기 (megi)
• Polish: sum
• Portuguese: peixe-gato
• Russian: сом (som)
• Serbian:

  Cyrillic: сом

  Roman: som

• Spanish: bagre, siluro, barbo
• Ukrainian: сом

Catfish (order Siluriformes) are a very diverse group of bony fish. Named for their prominent barbels, which give the image of cat-like whiskers, catfish range in size and behavior from the heaviest, the Mekong giant catfish in Southeast Asia and the longest, the wels catfish of Eurasia, to detritivores (species that eat dead material on the bottom), and even to a tiny parasitic species commonly called the candiru, Vandellia cirrhosa. There are armour-plated types and also naked types, neither having scales. Despite their common name, not all catfish have prominent barbels; what defines a fish as being in the order Siluriformes are in fact certain features of the skull and swimbladder. Catfish are of considerable commercial importance; many of the larger species are farmed or fished for food, and some are exploited for sport fishing, including a kind known as noodling. Many of the smaller species, particularly the genus Corydoras, are important in the aquarium hobby.

Taxonomy

The catfishes are a monophyletic group. This is supported by molecular evidence.

The taxonomy of catfishes is quickly changing. In a 2007 paper, Horabagrus, Phreatobius, and Conorhynchos'' were not classified under any current catfish families. There is disagreement on the family status of certain groups; for example, Nelson (2006) lists Auchenoglanididae and Heteropneustidae as separate families, while the All Catfish Species Inventory (ACSI) includes them under other families. Also, FishBase and the Integrated Taxonomic Information System lists Parakysidae as a separate family, while this group is included under Akysidae by both Nelson (2006) and ACSI. Many sources do not list the recently revised family Anchariidae. The family Horabagridae, including Horabagrus, Pseudeutropius, and Platytropius, is also not shown by some authors but presented by others as a true group.

The rate of description of new catfishes is at an all-time high. Between 2003 and 2005, over 100 species have been named, a rate three times faster than that of the past century. In June, 2005, researchers named the newest family of catfish, Lacantuniidae, only the third new family of fish distinguished in the last 70 years (others being the coelacanth in 1938 and the megamouth shark in 1983). The new species in Lacantuniidae, Lacantunia enigmatica, was found in the Lacantun river in Chiapas, Mexico.

Relationships between families

The relationship between the families is relatively unknown. Classifications of superfamilies varies. Many catfish families are classified into their own superfamilies.

Evolution

A large number of species of catfishes have been named from complete or partial skeletal fossils or even from only otoliths. The order dispersed early throughout the continents primarily through land bridges.

Distribution and habitat

Extant catfish species live in inland or coastal waters of every continent except Antarctica. Catfish have inhabited all continents at one time or another. One such species is Phreatobius cisternarum, known to live underground in phreatic habitats. Numerous species from the families Ariidae and Plotosidae, and a few species from among the Aspredinidae and Bagridae, are also found in marine environments.

Ecology

Most catfish are benthic in nature, meaning they normally associate with the bottom of the water column.

A wide range of feeding behaviors and diets are represented by the catfishes. In the family Trichomycteridae alone, there are species that feed on algae, fish scales, mucus, carrion, insects, or even blood in the infamous candirú. Panaque and some species of Hypostomus are unique among catfishes in that are the only fishes able to eat and digest wood. Members of the aspredinid genus Amaralia are known to specialize in feeding on loricariid eggs.

Representatives of several catfish families utilize their pectoral spines to produce stridulatory sounds by rubbing a ridged process of the pectoral spine within the cleithral groove, including members of Aspredinidae, Mochokidae, Doradidae, Pimelodidae, and Ictaluridae. Catfishes make a "creaking" sound during defense or appeasement behavior when being attacked by conspecifics. They also vocalize when they are captured or prodded.

In catfishes, fertilization of eggs can be internal, external, or even include sperm passage through female digestive tracts, the so called sperm drinking type of fertilization. Internal insemination is probable in all species of Auchenipteridae. In most of Ariidae, if not all species, the male is a mouthbrooder; he carries the relatively large eggs in his mouth until the young hatch.

All catfish, except members of Malapteruridae (electric catfish), possess a strong, hollow, bonified leading spine-like ray on their dorsal and pectoral fins. As a defense, these spines may be locked into place so that they stick outwards, which can inflict severe wounds. This venom is produced by glandular cells in the epidermal tissue covering the spines.

Sexual dimorphism is reported in about half of all families of catfish. The modification of the anal fin into an intromittent organ (in internal fertilizers) as well as accessory structures of the reproductive apparatus (in both internal and external fertilizers) have been described in species belonging to 11 different families. The giant Mekong catfish are not well studied since they live in developing countries and it is quite possible that they can grow even larger.

Internal anatomy

In many catfishes, the humeral process is a bony process extending backward from the pectoral girdle immediately above the base of the pectoral fin. It lies beneath the skin where its outline may be determined by dissecting the skin or probing with a needle.

The retina of catfish are composed of single cones and large rods. Many catfish have a tapetum lucidum which may help enhance photon capture and increase low-light sensitivity. Double cones, though present in most teleosts are absent from catfish.

The anatomical organization of the testis in catfish is variable among the families of catfish, but the majority of them present fringed testis: Ictaluridae, Claridae, Auchenipteridae, Doradidae, Pimelodidae, and Pseudopimelodidae. Fringes of the caudal region may present tubules, in which the lumen is filled by secretion and spermatozoa.

Catfish as food

Catfish have been widely caught and farmed for food for hundreds of years in Africa, Asia, Europe, and North America. Judgments as to the quality and flavor vary, with some food critics considering catfish as being excellent food, others dismiss them as watery and lacking in flavour. In Central Europe, catfish were often viewed as a delicacy to be enjoyed on feast days and holidays. Catfish are not Kosher, because the adult fish have no scales. Migrants from Europe and Africa to the United States brought along this tradition, and in the southern United States catfish is an extremely popular food. The most commonly eaten species in the United States are the channel catfish and blue catfish, both of which are common in the wild and increasingly widely farmed. Catfish is eaten in a variety of ways; in Europe it is often cooked in similar ways to carp, but in the United States it is typically crumbed with cornmeal and fried.

Catfish is also high in Vitamin D.

Aquaculture

Catfish are easy to farm in warm climates, leading to inexpensive and safe food at local grocers. Ictalurids are cultivated in North America (especially in the Deep South, with Mississippi being the largest domestic catfish producer). Channel catfish (Ictalurus punctatus) supports a $450 million/yr aquaculture industry.

In Asia, many catfish species are important as food. Several walking catfish (Clariidae) and shark catfish (Pangasiidae) species are heavily cultured in Africa and Asia. Exports of one particular shark catfish species from Vietnam, Pangasius bocourti, has met with pressures from the U.S. catfish industry. In 2003, The United States Congress passed a law preventing the imported fish from being labeled as catfish. As a result, the Vietnamese exporters of this fish now label their products sold in the U.S. as "basa fish." Trader Joe's has labeled frozen fillets of Vietnamese Pangasius Hypothalmus as "striper."http://www.growfish.com.au/content.asp?contentid=5816

There is a large and growing ornamental fish trade, with hundreds of species of catfish, such as Corydoras and armored suckermouth catfish (often called plecos), being a popular component of many aquaria. Other catfish commonly found in the aquarium trade are banjo catfish, talking catfish, and long-whiskered catfish.

Catfish as invasive species

Representatives of the genus Ictalurus have been misguidedly introduced into European waters in the hope of obtaining a sporting and food resource. However, the European stock of American catfishes has not achieved the dimensions of these fishes in their native waters, and have only increased the ecological pressure on native European fauna. Walking catfish have also been introduced in the freshwaters of Florida, with the voracious catfish becoming a major alien pest there. Flathead catfish, Pylodictis olivaris, is also a North American pest on Atlantic slope drainages.

References

External links

• Planet Catfish
• All Catfish Species Inventory