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Tilapia (/tɪˈlɑːpiə/ tih-LAH-pee-ə) is the common name for nearly a hundred species of cichlid fish from the coelotilapine, coptodonine, heterotilapine, oreochromine, pelmatolapiine, and tilapiine tribes (formerly all were “Tilapiini”), with the economically most important species placed in the Coptodonini and Oreochromini.^[2] Tilapia are mainly freshwater fish inhabiting shallow streams, ponds, rivers, and lakes, and less commonly found living in brackish water. Historically, they have been of major importance in artisanal fishing in Africa, and they are of increasing importance in aquaculture and aquaponics. Tilapia can become a problematic invasive species in new warm-water habitats such as Australia,^[3] whether deliberately or accidentally introduced, but generally not in temperate climates due to their inability to survive in cold water.

Traditionally a popular and affordable food in the Philippines with a mild taste, tilapia has been the fourth-most consumed fish in the United States since 2002, favored for its low cost and easy preparation. It is commonly fried or broiled as part of a dish.

Etymology

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The common name “tilapia” is based on the name of the cichlid genus Tilapia, which is itself a latinization of either tlhapi, the Tswana word for “fish”,^[4] or the Greek word “tilon,” referring to a fish mentioned by Aristotle, combined with “apios,” meaning “distant”.^[5] Scottish zoologist Andrew Smith named the genus in 1840.^[6]

History

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The aquaculture of Nile tilapia dates from Ancient Egypt, where it was represented by the hieroglyph K1, of the Gardiner list: 𓆛.

The fish symbolized rebirth in Egyptian art, and was associated in Egyptian belief-systems with Hathor, goddess of fertility and abundance.^[7] The tilapia was also said to accompany and protect the sun god on his daily journey across the sky.^[8]

Tilapia were one of the three main types of fish caught in Talmudic times from the Sea of Galilee, specifically the Galilean comb (Sarotherodon galilaeus). It is sometimes known by the name “St. Peter’s fish”, which comes from the narrative in the Gospel of Matthew about the apostle Peter catching a fish that carried a coin in its mouth. Though the passage does not name the fish, several tilapia species are found in the Sea of Galilee, where the narrative recounts the event took place. These species have been the target of small-scale artisanal fisheries in the area for thousands of years.^[9][10]

Characteristics

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Tilapia typically have laterally compressed, deep bodies. Like other cichlids, their lower pharyngeal bones are fused into a single tooth-bearing structure. A complex set of muscles allows the upper and lower pharyngeal bones to be used as a second set of jaws for processing food (cf. morays), allowing a division of labor between the “true jaws” (mandibles) and the “pharyngeal jaws“. This means they are efficient feeders that can capture and process a wide variety of food items.^[11] Their mouths are protrusible, usually bordered with wide and often swollen lips. The jaws have conical teeth. Typically, tilapia have a long dorsal fin, and a lateral line that often breaks towards the end of the dorsal fin, and starts again two or three rows of scales below. Some Nile tilapia can grow as long as 60 centimetres (2 ft).^[12]

Other than their temperature sensitivity, tilapia exist in or can adapt to a very wide range of conditions. An extreme example is the Salton Sea, where tilapia introduced when the water was merely brackish now live in salt concentrations so high that other marine fish cannot survive.^[13]

Tilapia are also known to be mouth-brooding species, which means they carry the fertilized eggs and young fish in their mouths for several days after the yolk sac is absorbed.^[12]

Species

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Historically, all tilapia have been included in their namesake genus Tilapia.^[2] In recent decades, some were moved into a few other genera, notably Oreochromis,^[14] and Sarotherodon.^[15] Even with this modification, apparently Tilapia was strongly poly– or paraphyletic.^[16] In 2013, a major taxonomic review resolved this by moving most former Tilapia spp. to several other genera. As a consequence, none of the species that are of major economic importance remain in Tilapia, but are instead placed in Coptodon, Oreochormis, and Sarotherodon.^[2]

Exotic and invasive species

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See also: Tilapia as exotic species

Tilapia have been used as biological controls for certain aquatic plant problems. They have a preference for a floating aquatic plant, duckweed (Lemna spp.), but also consume some filamentous algae.^[17] In Kenya, tilapia were introduced to control mosquitoes, which were causing malaria, because they consume mosquito larvae, consequently reducing the numbers of adult female mosquitoes, the vector of the disease.^[18] These benefits are, however, frequently outweighed by the negative aspects of tilapia as invasive species.^[19]

Tilapia are unable to survive in temperate climates because they require warm water. The pure strain of the blue tilapia, Oreochromis aureus, has the greatest cold tolerance and dies at 7 °C (45 °F), while all other species of tilapia die at a range of 11 to 17 °C (52 to 62 °F). As a result, they cannot invade temperate habitats and disrupt native ecologies in temperate zones; however, they have spread widely beyond their points of introduction in many fresh and brackish tropical and subtropical habitats, often disrupting native species significantly.^[20] Because of this, tilapia are on the IUCN‘s 100 of the World’s Worst Alien Invasive Species list.^[21] In the United States, tilapia are found in much of the south, especially Florida and Texas, and as far north as Idaho, where they survive in power-plant discharge zones.^[22] Tilapia are also currently stocked in the Phoenix, Arizona, canal system as an algal growth-control measure. In a Washington, D.C. fishing report from 21 June 2024, it was reported that an angler caught a Tilapia on a crankbait at the Jones Point Park under the Woodrow Wilson Bridge,^[23] which is on the Potomac River. Many state fish and wildlife agencies in the United States, Australia, South Africa, and elsewhere consider them to be invasive species.^[24]

Aquarium species

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Larger tilapia species are generally poor community aquarium fish because they eat plants, dig up the bottom, and fight with other fish. The larger species are often raised as a food source, though, because they grow rapidly and tolerate high stocking densities and poor water quality.

Smaller West African species, such as Coelotilapia joka and species from the crater lakes of Cameroon, are more popular as aquarium fish. In specialised cichlid aquaria, tilapia can be mixed successfully with nonterritorial cichlids, armored catfish, tinfoil barbs, garpike, and other robust fish. Some species, including Heterotilapia buttikoferi, Coptodon rendalli, Pelmatolapia mariae, C. joka, and the brackish-water Sarotherodon melanotheron, have attractive patterns and are quite decorative.^[25]

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Commercial species

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Tilapia were originally farmed in their native Africa and Levant. Fast-growing, tolerant of stocking density, and adaptable, tilapia have been introduced to and are farmed extensively in many parts of Asia and are increasingly common aquaculture targets elsewhere.

hidePrincipal commercial tilapia species
Common name	Scientific name	Maximum length	Common length	Maximum weight	Maximum age	Trophic level	Fish Base	FAO	WoRMS	IUCN status
Nile tilapia	Oreochromis niloticus (Linnaeus, 1758)	60 cm	cm	4.324 kg	9 years	2.0	[26]	[27][28]	[29]	Least Concern[30]
Blue tilapia	– Oreochromis aureus       (Steindachner, 1864)	45.7 cm	16 cm	2.010 kg	years	2.1	[31]		[32]	Least Concern[33]
Nile tilapia + blue tilapia hybrid		cm	cm	kg	years
Mozambique tilapia	Oreochromis mossambicus (Peters, 1852)	39 cm	35 cm	1.130 kg	11 years	2.0	[34]	[35]	[36]	Vulnerable[37]

Global harvest of tilapia species in million tonnes as reported by the FAO, 1950–2009 ^[38]

↑ Wild capture

↑ Aquaculture production

Aquaculture

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Main article: Aquaculture of tilapia

Farmed tilapia production in 2002 worldwide was about 1.5 million tonnes (1.7 million short tons) annually, with an estimated value of US$1.8 billion,^[39] about equal to those of salmon and trout.

Unlike carnivorous fish, tilapia can feed on algae or any plant-based food. This reduces the cost of tilapia farming, reduces fishing pressure on prey species, avoids concentrating toxins that accumulate at higher levels of the food chain, and makes tilapia the preferred “aquatic chickens” of the trade.^[40]

Because of their large size, rapid growth, and palatability, tilapia cichlids are the focus of major farming efforts, specifically various species of Oreochromis, Sarotherodon, and Coptodon (all were formerly in the namesake genus Tilapia).^[2] Like other large fish, they are a good source of protein and popular among artisanal and commercial fisheries. Most such fisheries were originally found in Africa, but outdoor fish farms in tropical countries, such as Papua New Guinea, the Philippines, and Indonesia, are underway in freshwater lakes.^[41] In temperate zone localities, tilapiine farming operations require energy to warm the water to tropical temperatures. One method uses waste heat from factories and power stations.^{[42][failed verification]}

At 1.3 million tonnes per annum, China is the largest tilapia producer in the world, followed by Egypt with 0.5 million.^[43] The US, by comparison, produces 10 thousand tonnes against a consumption of 2.5 million.^[38]

In modern aquaculture, wild-type Nile tilapia are not too often seen, as the dark color of their flesh is not much desired by many customers, and because it has a bit of a reputation of being a rough fish associated with poverty.^[44] However, they are fast-growing and give good fillets; leucistic (“red”) breeds which have lighter meat have been developed and are very popular.

Hybrid stock is also used in aquaculture; Nile × blue tilapia hybrids are usually rather dark, but a light-colored hybrid breed known as “Rocky Mountain White” tilapia is often grown due to its very light flesh and tolerance of low temperatures.^[44]

Commercially grown tilapia are almost exclusively male, typically done by adding male sex hormone in the food to the tilapia fry, causing any potential female tilapia to change sex to male.^[28][45] It can also be achieved through hybridization of certain tilapia species or the use of so-called “supermales” that have homozygous male sex chromosomes (resulting in all their offspring receiving a male sex chromosome and thus becoming males).^[45][46] Males are preferred because they grow much faster than females.^[28] Additionally, because tilapia are prolific breeders, the presence of female tilapia results in rapidly increasing populations of small fish, rather than a stable population of harvest-size animals.^{[47][unreliable source?]}

Tilapia, as a “traditional” dish, was first introduced in the Philippines in 1950 with Mozambique tilapia followed by Nile tilapia in 1972 from Thailand. Strains such as terapon (gunggong) and white goby (biyang puti) were abundant in Laguna de Bay. In 1988, WorldFish, Filipino and Norwegian researchers started aquaculture of the Genetically Improved Farmed Tilapia (GIFT).^[48]

Other methods of tilapia population control are polyculture, with predators farmed alongside tilapia or hybridization with other species.^[49]

As food

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Tilapia, introduced to the state of Tamil Nadu, India in the 1950s as a cheap protein source, quickly spread across the state’s freshwater bodies because of its ability to thrive in polluted, low-oxygen environments.^[50]

The Fisheries Research Committee has recommended the culture of this fish only in areas in the western slopes of the Western Ghats and the coastal strip between Cape Comorin and south of and excluding river Tapti, and in districts of Tinnevellv, Madurai and Ramnad in Madras south of and including river Vaigai. The committee has suggested further investigation to enable it to examine the question of desirability of Tilapia culture in other parts of India.^[51]

Whole tilapia fish can be processed into skinless, boneless fillets. In some of the commercial strains, the yield has been reported up to 47% at harvest weight.^[52][53]

Tilapia are among the commercially important aquaculture species that are susceptible to off-flavors (others include trout, barramundi, and channel catfish). These ‘muddy’ or ‘musty’ flavors are normally caused by geosmin and 2-methylisoborneol, organic products of ubiquitous cyanobacteria that are often present or bloom sporadically in water bodies and soil. These flavors are no indication of freshness or safety of the fish, but they make the product unattractive to consumers. Simple quality-control procedures are known to be effective in ensuring the quality of fish entering the market.^[54]

Tilapia have very low levels of mercury.^[55] Tilapia are low in saturated fat, calories, carbohydrates, and sodium, and are a good protein source. They also contain the micronutrients phosphorus, niacin, selenium, vitamin B₁₂, and potassium.^[56]

Tilapia may be a less nutritious fish than generally believed. The fish’s omega-3 fatty acid content is often far lower than that of other commonly eaten fish species. Their omega-6 fatty acid levels are unusually high. Multiple studies have evaluated the effects of adding flaxseed derivatives (a vegetable source of omega-3 fatty acids) to the feed of farmed tilapia. These studies have found both the more common omega-3 fatty acid found in the flax, ALA and the two types almost unique to animal sources (DHA and EPA), increased in the fish fed this diet.^[57][58] Guided by these findings, tilapia farming techniques could be adjusted to address the nutritional criticisms directed at the fish, while retaining its advantage as an omnivore capable of feeding on economically and environmentally inexpensive vegetable protein. Adequate diets for salmon and other carnivorous fish can alternatively be formulated from protein sources such as soybean, although soy-based diets with soy oil may also change in the balance between omega-6 and omega-3 fatty acids.^[59]

Ecological agent

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Tilapia serve as a natural, biological control for most aquatic plant problems. They consume floating aquatic plants, such as duckweed watermeal (Lemna spp.), most “undesirable” submerged plants, and most forms of algae.^[60] In the United States and countries such as Thailand, they are becoming the plant-control method of choice, reducing or eliminating the use of toxic chemicals and heavy metal-based algaecides. However, their environmental impact as an invasive species may outweigh their ecological benefit.^[61] Their tolerance for a wide range of environmental conditions allow them to thrive in polluted or otherwise degraded aquatic habitats.^[62][61] Arkansas stocks many public ponds and lakes to help with vegetation control.^{[citation needed]} In Kenya, tilapia help control mosquitoes, which carry malaria parasites.^[18]

Tilapia can be farmed with shrimp in a symbiotic manner, positively enhancing the productive output of both.^{[citation needed]}

Medical use

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In Brazil, Nile tilapia (Oreochromis niloticus) fish skin applied as a bandage is first used in a 2017 clinical trial to treat burn injuries,^[63] after successful trial in rats.^[64] In the United States, tilapia skin has been used to successfully treat third-degree wounds to the paws of two black bears caught in California’s Thomas wildfire,^[65][66] and also to treat burns on the paws of a black bear from California’s Carr wildfire.^[67] Nile tilapia skin has completed a phase III clinical trial for superficial partial-thickness burns. The fish skin group showed faster healing, lower pain, reduced dressing changes, and lower treatment costs compared to silver sulfadiazine cream control.^[68]

Nile tilapia skin has also been used in neovaginoplasty as a skin graft material, for Müllerian agenesis, vaginal stenosis, and gender-affirming surgery.^[69][70]

The skin-growing properties of tilapia skin are believed to be linked to its high type I collagen content and structural similarities to human skin. The material is also quite strong despite its low thickness.^[71] The current procedure for skin use^[68] calls for chemical sterilization with chlorhexidine, immersion in glycerol, followed by gamma ray sterilization, plus a few washes with saline in between.^[72]

Parasites

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As with most fish, tilapia harbor a variety of parasites. For the monogeneans, these especially include species of the megadiverse genus Cichlidogyrus, which are gill parasites. Species of Enterogyrus are parasites in the digestive system. Tilapia, as important aquaculture fishes, have been introduced widely all over the world, and often carried their monogenean parasites with them. In South China, a 2019 study has shown that nine species of monogeneans were carried by introduced tilapia.^[73]

Catfish (or catfishes; order Siluriformes /sɪˈljʊərɪfɔːrmiːz/ or Nematognathi) are a diverse group of ray-finned fish. Named for their prominent barbels, which resemble a cat‘s whiskers, catfish range in size and behavior from the three largest species alive, the Mekong giant catfish from Southeast Asia, the wels catfish of Eurasia, and the piraíba of South America, to detritivores (species that eat dead material on the bottom), and even to a tiny parasitic species commonly called the candiru, Vandellia cirrhosa. Neither the armour-plated types nor the naked types have scales. Despite their name, not all catfish have prominent barbels or “whiskers”. Members of the Siluriformes order are defined by features of the skull and swimbladder. Catfish are of considerable commercial importance; many of the larger species are farmed or fished for food. Many of the smaller species, particularly the genus Corydoras, are important in the aquarium hobby. Many catfish are nocturnal,^[6][7] but others (many Auchenipteridae) are crepuscular or diurnal (most Loricariidae or Callichthyidae, for example).

Taxonomy

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Molecular evidence suggests that in spite of the great morphological diversity in the order, all catfish form a monophyletic group.^[8] Catfish belong to a superorder called the Ostariophysi, which also includes the Cypriniformes (carps and minnows), Characiformes (characins and tetras), Gonorynchiformes (milkfish and beaked salmons) and Gymnotiformes (South American knifefish), a superorder characterized by the Weberian apparatus. Some place Gymnotiformes as a sub-order of Siluriformes; however, this is not as widely accepted. Currently, the Siluriformes are said to be the sister group to the Gymnotiformes, though this has been debated due to more recent molecular evidence.^[9] As of 2007 there were about thirty-six extant catfish families, and about 3,093 extant species have been described.^[10] This makes the catfish order the second or third most diverse vertebrate order; in fact, one out of every twenty vertebrate species is a catfish.^[11]

Catfish are believed to have a Gondwanan origin primarily centered around South America, as the most basal living catfish groups are known from there. The earliest known definitive members lived in the Americas from the Campanian to Maastrichtian stages of the Late Cretaceous, including the Andinichthyidae, Vorhisia vulpes and possibly Arius.^[1][12][13] A potential fossil record is known from the earlier Coniacian–Santonian stages in Niger of West Africa,^[2] though this has been considered unreliable,^[13] and the putative earliest armored catfish known from the fossil record, Afrocascudo, lived during the Cenomanian age of the Late Cretaceous in Morocco of North Africa (Kem Kem Group).^[3] The describers of Afrocascudo claimed that the presence of a derived loricariid so early on would indicate the extensive diversification of catfish, or at least loricarioids, prior to the beginning of the Late Cretaceous. As extant loricariids are only known from South America, much of this diversification must have occurred on the supercontinent of West Gondwana prior to its fragmentation into South America and Africa.^[3] Britz and colleagues suggested that Afrocascudo instead represents a juvenile obaichthyid lepisosteiform, possibly a junior synonym of Obaichthys.^[14] The authors of the original study still stood by their original conclusion based on the absence of important holostean characters, and noted that it could not be a juvenile, since the bones were completely ossified.^[15]

The taxonomy of catfish is quickly changing. In a 2007 and 2008 paper, Horabagrus, Phreatobius, and Conorhynchos were not classified under any current catfish families.^[10] 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. 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.^{[9][16][17][18]} Many sources do not list the recently revised family Anchariidae.^[19] The family Horabagridae, including Horabagrus, Pseudeutropius, and Platytropius, is not shown by some authors but presented by others as a true group.^[8] Thus, the actual number of families differs between authors. The species count is in constant flux due to taxonomic work as well as description of new species.^[9] Between 2003 and 2005, over one hundred species were named, a rate three times faster than that of the past century.^[20] In June 2005, researchers named the newest family of catfish, Lacantuniidae, only the third new family of fish distinguished in the last seventy years, the 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 the Mexican state of Chiapas.^[21]

The higher-level phylogeny of Siluriformes has gone through several recent changes, mainly due to molecular phylogenetic studies. While most studies, both morphological and molecular, agree that catfishes are arranged into three main lineages, the relationship among these lineages has been a contentious point in which these studies, performed for example by Rui Diogo, differ.^{[22][23][24][25][26]} The three main lineages in Siluriformes are the family Diplomystidae, the denticulate catfish suborder Loricarioidei (containing the Neotropical “suckermouth” catfishes), and the suborder Siluroidei, which contains the remaining families of the order. According to morphological data, Diplomystidae is usually considered to be the earliest branching catfish lineage and the sister group to the other two lineages, Loricarioidei and Siluroidei.^[25][26][27] Molecular evidence usually contrasts with this hypothesis, and shows the suborder Loricarioidei as the earliest branching catfish lineage, and sister to a clade that includes the Diplomystidae and Siluroidei; this phylogeny has been obtained in numerous studies based on genetic data.^{[8][22][23][28]} However, it has been suggested that these molecular results are errors as a result of long branch attraction, incorrectly placing Loricarioidei as the earliest-branching catfish lineage.^[24] When a data filtering method^[29] was used to reduce lineage rate heterogeneity (the potential source of bias) on their dataset, a final phylogeny was recovered which showed the Diplomystidae are the earliest-branching catfish, followed by Loricarioidei and Siluroidei as sister lineages, providing both morphological and molecular support for Diplomystidae being the earliest branching catfish.^[24]

Below is a list of family relationships by different authors. Lacantuniidae is included in the Sullivan scheme based on recent evidence that places it sister to Claroteidae.^[30]

Nelson, 2006[9]Sullivan et al., 2006[8]Unresolved familiesCetopsidaePseudopimelodidaeHeptapteridaeCranoglanididaeIctaluridaeLoricarioideaAmphiliidaeTrichomycteridaeNematogenyiidaeCallichthyidaeScoloplacidaeAstroblepidaeLoricariidaeSisoroideaAmblycipitidaeAkysidaeSisoridaeErethistidaeAspredinidaeDoradoideaMochokidaeDoradidaeAuchenipteridaeSiluroideaSiluridaeMalapteruridaeAuchenoglanididaeChacidaePlotosidaeClariidaeHeteropneustidaeBagroideaAustroglanididaeClaroteidaeAriidaeSchilbeidaePangasiidaeBagridaePimelodidaeUnresolved familiesCetopsidaePlotosidaeChacidaeSiluridaePangasiidaeSuborder LoricarioideiTrichomycteridaeNematogenyiidaeCallichthyidaeScoloplacidaeAstroblepidaeLoricariidaeClarioideaClariidaeHeteropneustidaeArioideaAriidaeAnchariidaePimelodoideaPimelodidaePseudopimelodidaeHeptapteridaeConorhynchosIctaluroideaIctaluridaeCranoglanididaeDoradoidea (sister to Aspredinidae)DoradidaeAuchenipteridae”Big Asia”SisoroideaAmblycipitidaeAkysidaeSisoridaeErethistidaeAilia + Laides (Asian schilbeids)Horabagridae (Horabagrus + Pseudeutropius + Platytropius)Bagridae (without Rita)”Africa”MochokidaeMalapteruridaeAmphiliidaeClaroteidaeLacantuniidaeSchilbeidae

Phylogeny

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Phylogeny of living Siluriformes based on 2017^[31] and extinct families based on Nelson, Grande & Wilson 2016.^[32]

Siluriformes

†AndinichthyidaeLoricaroideiNematogenyidae Trichomycteridae Callichthyidae Astroblepidae Loricariidae DiplomystoideiDiplomystidae†BachmanniidaeSiluroideiHypsidoroidea†HypsidoridaeCetopsoideaCetopsidae SiluroideaSiluridae ArioideaPangasiidaeBig African catfishesMochokidae ClaroteidaeIctaluroideaPlotosidaeIctaluridae ClarioideaClariidae SisoroideaAiliidaeSisoridae Bagridae DoradoideaAspredinidaeDoradidae Auchenipteridae PimelodoideaHeptapteridae Pseudopimelodidae Pimelodidae

Unassigned families:

• Bachmanniidae†
• Scoloplacidae (Loricarioidei)
• Akysidae (Sisoroidea)
• Amblycipitidae (Sisoroidea)
• Anchariidae (Arioidea)
• Ariidae (Arioidea)
• Amphiliidae (Big African catfishes)
• Austroglanididae (Arioidea)
• Chacidae (Siluroidei)
• Conorhynchos (Pimelodoidea)
• Cranoglanididae (Ictaluroidea)
• Heteropneustidae (Clarioidea)
• Horabagridae (Sisoroidea)
• Kryptoglanidae (Siluroidea)
• Lacantuniidae (Big African catfishes)
• Malapteruridae (Big African catfishes)
• Phreatobiidae (Pimelodoidea)
• Rita (Sisoroidea)
• Schilbeidae (Big African catfishes)

Ecology

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Distribution and habitat

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Extant catfish species live inland or in coastal waters of every continent except Antarctica. Catfish have inhabited all continents at one time or another.^[9] They are most diverse in tropical South America, Asia, and Africa, with one family native to North America and one family in Europe.^[11] More than half of all catfish species live in the Americas. They are the only ostariophysans that have entered freshwater habitats in Madagascar, Australia, and New Guinea.^[33]

They are found in fresh water/brackish water environments, though most inhabit shallow, running water.^[33] Representatives of at least eight families are hypogean (live underground) with three families that are also troglobitic (inhabiting caves).^[34][35] One such species is Phreatobius cisternarum, known to live underground in phreatic habitats.^[36] Numerous species from the families Ariidae and Plotosidae, and a few species from among the Aspredinidae and Bagridae, are found in salt water.^[37][38]

In the Southern United States, catfish species may be known by a variety of slang names, such as “mud cat”, “polliwogs”, or “chuckleheads”.^[39] These nicknames are not standardized, so one area may call a bullhead catfish by the nickname “chucklehead”, while in another state or region, that nickname refers to the blue catfish.^[40]

As invasive species

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Representatives of the genus Ictalurus have been introduced into European waters in the hope of obtaining a sporting and food resource, but the European stock of American catfishes has not achieved the dimensions of these fish in their native waters and have only increased the ecological pressure on native European fauna. Walking catfish have also been introduced in the freshwater areas 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.^[11] Pterygoplichthys species, released by aquarium fishkeepers, have also established feral populations in many warm waters around the world.^{[41][42][43][44][45]}

Physical characteristics

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External anatomy of catfish

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Most catfish are bottom feeders. In general, they are negatively buoyant, which means that they usually sink rather than float due to a reduced gas bladder and a heavy, bony head.^[33] Catfish have a variety of body shapes, though most have a cylindrical body with a flattened ventrum to allow for benthic feeding.^[33]

A flattened head allows for digging through the substrate, as well as perhaps serving as a hydrofoil. Some have a mouth that can expand to a large size and contains no incisiform teeth; catfish generally feed through suction or gulping rather than biting and cutting prey.^[33] Some families, though, notably the Loricariidae and Astroblepidae, have a suckermouth that allows them to fasten themselves to objects in fast-moving water. Catfish also have a maxilla reduced to a support for barbels; this means that they are unable to protrude their mouths as other fish such as carp.^[33]

Catfish may have up to four pairs of barbels – nasal, maxillary (on each side of mouth), and two pairs of chin barbels, though pairs of barbels may be absent depending on the species. Catfish barbels always occur in pairs. Many larger catfish also have chemoreceptors across their entire bodies, which means they “taste” anything they touch and “smell” any chemicals in the water. “In catfish, gustation plays a primary role in the orientation and location of food”.^[46] Because their barbels and chemoreception are more important in detecting food, the eyes on catfish are generally small. Like other ostariophysans, they are characterized by the presence of a Weberian apparatus.^[9] Their well-developed Weberian apparatus and reduced gas bladder allow for improved hearing and sound production.^[33]

Catfish do not have scales; their bodies are often naked. In some species, their mucus-covered skin is used in cutaneous respiration, where the fish breathes through its skin.^[33] In some catfish, the skin is covered in bony plates called scutes; some form of body armor appears in various ways within the order. In loricarioids and in the Asian genus Sisor, the armor is primarily made up of one or more rows of free dermal plates. Similar plates are found in large specimens of Lithodoras. These plates may be supported by vertebral processes, as in scoloplacids and in Sisor, but the processes never fuse to the plates or form any external armor. By contrast, in the subfamily Doumeinae (family Amphiliidae) and in hoplomyzontines (Aspredinidae), the armor is formed solely by expanded vertebral processes that form plates. Finally, the lateral armor of doradids, Sisor, and hoplomyzontines consists of hypertrophied lateral line ossicles with dorsal and ventral lamina.^[47]

All catfish other than members of the Malapteruridae (electric catfish), possess a strong, hollow, bony, 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, enabling them to inflict severe wounds.^[11] In numerous catfish species, these fin rays can be used to deliver a stinging protein if the fish is irritated;^[48] as many as half of all catfish species may be venomous in this fashion, making the Siluriformes overwhelmingly the vertebrate order with the largest number of venomous species.^[49] This venom is produced by glandular cells in the epidermal tissue covering the spines.^[9] In members of the family Plotosidae and of the genus Heteropneustes, this protein is so strong it may hospitalize humans who receive a sting; in Plotosus lineatus, the stings can be lethal.^[9] The dorsal- and pectoral-fin spines are two of the most conspicuous features of siluriforms, and differ from those in other fish groups.^[50] Despite the widespread use of the spines for taxonomic and phylogenetic studies the fields have struggled to effectively use the information due to a lack of consistency in the nomenclature, with a general standard for the descriptive anatomy of catfish spines proposed in 2022 to try and resolve this problem.^[50]

Juvenile catfish, like most fish, have relatively large heads, eyes, and posterior median fins in comparison to larger, more mature individuals. These juveniles can be readily placed in their families, particularly those with highly derived fin or body shapes; in some cases, identification of the genus is possible. As far as known for most catfish, features that are often characteristic of species, such as mouth and fin positions, fin shapes, and barbel lengths, show little difference between juveniles and adults. For many species, pigmentation pattern is also similar in juveniles and adults. Thus, juvenile catfish generally resemble and develop smoothly into their adult form without distinct juvenile specializations. Exceptions to this are the ariid catfish, where the young retain yolk sacs late into juvenile stages, and many pimelodids, which may have elongated barbels and fin filaments or coloration patterns.^[51]

Sexual dimorphism is reported in about half of all families of catfish.^[52] 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.^[53]

Size

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Catfish have one of the largest ranges in size within a single order of bony fish.^[33] Many catfish have a maximum length of under 12 cm (4.7 in).^[9] Some of the smallest species of the Aspredinidae and Trichomycteridae reach sexual maturity at only 1 cm (0.39 in).^[11]

The wels catfish, Silurus glanis, and the much smaller related Aristotle’s catfish, are the only catfish indigenous to Europe; the former ranges throughout Europe, and the latter is restricted to Greece. Mythology and literature record wels catfish of astounding proportions yet are to be proven scientifically. The typical size of the species is about 1.2–1.6 m (3.9–5.2 ft), and fish more than 2 m (6.6 ft) are rare. However, they are known to exceed 2.5 m (8.2 ft) in length and 100 kg (220 lb) in weight. In July 2009, a catfish weighing 88 kilograms (194 lb) was caught in the River Ebro, Spain, by an 11-year-old British schoolgirl.^[54]

In North America, the largest Ictalurus furcatus (blue catfish) caught in the Missouri River on 20 July 2010, weighed 59 kg (130 lb). The largest flathead catfish, Pylodictis olivaris, ever caught was in Independence, Kansas, weighing 56 kg (123 lb).

These records pale in comparison to a Mekong giant catfish caught in northern Thailand on 1 May 2005, and reported to the press almost 2 months later, that weighed 293 kilograms (646 lb). This is the largest giant Mekong catfish caught since Thai officials started keeping records in 1981.^[55] Also in Asia, Jeremy Wade caught a 75.5-kilogram (166.4 lb) goonch following three fatal attacks on humans in the Kali River on the India–Nepal border. Wade was of the opinion that the offending fish must have been significantly larger than this to have taken an 18-year-old boy, as well as a water buffalo.^{[citation needed]}

Piraíba (Brachyplatystoma filamentosum) can grow exceptionally large and are native to the Amazon Basin. They can occasionally grow to 200 kg (440 lb), as evidenced by numerous catches. Deaths from being swallowed by these fish have been reported in the region.

Internal anatomy

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In many catfish, 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.^[56]

The retinae 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.^[57]

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.^[58] In the testes of some species of Siluriformes, organs and structures such as a spermatogenic cranial region and a secretory caudal region are observed, in addition to the presence of seminal vesicles in the caudal region.^[59] The total number of fringes and their length are different in the caudal and cranial portions between species.^[58] Fringes of the caudal region may present tubules, in which the lumen is filled by secretion and spermatozoa.^[58] Spermatocysts are formed from cytoplasmic extensions of Sertoli cells; the release of spermatozoa is allowed by breaking of the cyst walls.^[58]

The occurrence of seminal vesicles, in spite of their interspecific variability in size, gross morphology, and function, has not been related to the mode of fertilization. They are typically paired, multichambered, and connected with the sperm duct, and have been reported to play glandular and storage functions. Seminal vesicle secretion may include steroids and steroid glucuronides, with hormonal and pheromonal functions, but it appears to be primarily constituted of mucoproteins, acid mucopolysaccharides, and phospholipids.^[53]

Fish ovaries may be of two types – gymnovarian or cystovarian. In the first type, the oocytes are released directly into the coelomic cavity and then eliminated. In the second type, the oocytes are conveyed to the exterior through the oviduct.^[59] Many catfish are cystovarian in type, including Pseudoplatystoma corruscans, P. fasciatum, Lophiosilurus alexandri, and Loricaria lentiginosa.^[58][59]

Communication

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Catfish can produce different types of sounds and also have well-developed auditory reception used to discriminate between sounds with different pitches and velocities. They are also able to determine the distance of the sound’s origin and from what direction it originated.^[60] This is a very important fish communication mechanism, especially during agonistic and distress behaviors. Catfish are able to produce a variety of sounds for communication that can be classified into two groups: drumming sounds and stridulation sounds. The variability in catfish sound signals differs due to a few factors: the mechanism by which the sound is produced, the function of the resulting sound, and physiological differences such as size, sex, and age.^[61] To create a drumming sound, catfish use an indirect vibration mechanism using a swimbladder. In these fishes, sonic muscles insert on the ramus Mulleri, also known as the elastic spring. The sonic muscles pull the elastic spring forward and extend the swimbladder. When the muscles relax, the tension in the spring quickly returns the swimbladder to its original position, which produces the sound.^[62]

Catfish also have a sound-generating mechanism in their pectoral fins. Many species in the catfish family possess an enhanced first pectoral fin ray, called the spine, which can be moved by large abductor and adductor muscles. The base of the catfishes’ spines has a sequence of ridges, and the spine normally slides within a groove on the fish’s pelvic girdle during routine movement; but, pressing the ridges on the spine against the pelvic girdle groove creates a series of short pulses.^[60][62] The movement is analogous to a finger moving down the teeth of a comb, and consequently a series of sharp taps is produced.^[61]

Sound-generating mechanisms are often different between the sexes. In some catfish, pectoral fins are longer in males than in females of similar length, and differences in the characteristic of the sounds produced were also observed.^[62] Comparison between families of the same order of catfish demonstrated family and species-specific patterns of vocalization, according to a study by Maria Clara Amorim. During courtship behavior in three species of Corydoras catfish, all males actively produced stridulation sounds before egg fertilization, and the species’ songs were different in pulse number and sound duration.^[63]

Sound production in catfish may also be correlated with fighting and alarm calls. According to a study by Kaatz, sounds for disturbance (e.g. alarm) and agonistic behavior were not significantly different, which suggests distress sounds can be used to sample variation in agonistic sound production.^[63] However, in a comparison of a few different species of tropical catfish, some fish put under distress conditions produced a higher intensity of stridulatory sounds than drumming sounds.^[64] Differences in the proportion of drumming versus stridulation sounds depend on morphological constraints, such as different sizes of drumming muscles and pectoral spines. Due to these constraints, some fish may not even be able to produce a specific sound. In several different species of catfish, aggressive sound production occurs during cover site defense or during threats from other fish. More specifically, in long-whiskered catfish, drumming sounds are used as a threatening signal and stridulations are used as a defense signal. Kaatz investigated 83 species from 14 families of catfish, and determined that catfish produce more stridulatory sounds in disturbance situations and more swimbladder sounds in intraspecific conflicts.^[64]

Economic importance

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Aquaculture

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Main article: Aquaculture of catfish

Catfish are easy to farm in warm climates, leading to inexpensive and safe food at local grocers. About 60% of U.S. farm-raised catfish are grown within a 65-mile (100-km) radius of Belzoni, Mississippi.^[65] Channel catfish (Ictalurus punctatus) supports a $450 million/yr aquaculture industry.^[11] The largest producers are located in the Southern United States, including Mississippi, Alabama, and Arkansas.^[66]

Catfish raised in inland tanks or channels are usually considered safe for the environment, since their waste and disease should be contained and not spread to the wild.^[67]

In Asia, many catfish species are important as food. Several airbreathing 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, have 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.^[68] 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 hypophthalmus as “striper.”^[69]

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 food

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Wikibooks Cookbook has a recipe/module on

• Catfish

Catfish have widely been caught and farmed for food for thousands of years in Africa, Asia, Europe, and North America. Judgments as to the quality and flavor vary, with some food critics considering catfish excellent to eat, while others dismiss them as watery and lacking in flavor.^[70] Catfish is high in vitamin D.^[71] Farm-raised catfish contains low levels of omega-3 fatty acids and a much higher proportion of omega-6 fatty acids.^[72]

In Central Europe, catfish were often viewed as a delicacy to be enjoyed on feast days and holidays. 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 the blue catfish, both of which are common in the wild and increasingly widely farmed. Farm-raised catfish became such a staple of the U.S. diet that President Ronald Reagan proclaimed National Catfish Day on June 25, 1987, to recognize “the value of farm-raised catfish.”^[73]

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 popularly crumbed with cornmeal and fried.^[70]

In Indonesia, catfish is usually served fried or grilled in street stalls called warung and eaten with vegetables, sambal (a spicy relish or sauce), and usually nasi uduk (traditional coconut rice). The dish is called pecel lele or pecak lele. Lele is the Indonesian word for catfish. The same dish can also be called as lele penyet (squashed catfish) if the fish is lightly squashed along with sambal with a stone mortar-and-pestle. The pecel or pecak version presents the fish in a separate plate while the mortar is solely for sambal.

In Malaysia, catfish is called ikan keli and is fried with spices or grilled and eaten with tamarind and Thai chili gravy and is also often eaten with steamed rice.

In Bangladesh and the Indian states of Odisha, West Bengal and Assam, catfish (locally known as magur) is eaten as a favored delicacy during the monsoons. In the Indian state of Kerala, the local catfish, known as thedu’ or etta in Malayalam, is also popular.

In Hungary, catfish is often cooked in paprika sauce (Harcsapaprikás) typical of Hungarian cuisine. It is traditionally served with pasta smothered with curd cheese (túrós csusza).

In Myanmar (formerly Burma), catfish is usually used in mohinga, a traditional noodle fish soup cooked with lemon grass, ginger, garlic, pepper, banana stem, onions, and other local ingredients.

Vietnamese catfish, of the genus Pangasius, cannot be legally marketed as catfish in the United States, and so is referred to as swai or basa.^[74] Only fish of the family Ictaluridae may be marketed as catfish in the United States.^[75][76] In the UK, Vietnamese catfish is sometimes sold as “Vietnamese river cobbler”, although more commonly as Basa.^[77]

In Nigeria, catfish is often cooked in a variety of stews. It is particularly cooked in a delicacy popularly known as “catfish pepper soup” which is enjoyed throughout the nation.^[78]

In Jewish dietary law, known as kashrut, fish must have fins and scales to be kosher.^[79] Since catfish lack scales, they are not kosher.^[80]

Mythology

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In the mythology of the Japanese Shinto religion natural phenomenon are caused by kami. Earthquakes are caused by a giant catfish called Namazu. There are other kami associated with earthquakes. In Kyoto it’s usually an eel, but after the 1855 Edo earthquake Namazu-e (鯰絵, “catfish prints”) were printed giving more popularity to the catfish kami that has been known since the 16th century Otsu-e.^[81] In one catfish print the divine white horse of Amaterasu is depicted knocking down the earthquake-causing catfish.^[82]

Dangers to humans

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While the vast majority of catfish are harmless to humans, a few species are known to present some risk. Many catfish species have “stings” (actually non-venomous in most cases) embedded behind their fins; thus precautions must be taken when handling them. Stings by the venomous striped eel catfish have killed people in rare cases.^[83]

Catfish fishing records

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By information from International Game Fish Association IGFA the most outstanding record:^[84]

• The biggest flathead catfish caught was by Ken Paulie in the Elk City Reservoir in Kansas, US on 19 May 1998 that weighed 55.79 kg (123 lb 0 oz)