Tilapia

Tilapiine cichlids
Nile tilapia (Oreochromis niloticus niloticus)
Scientific classification
Kingdom: Animalia Phylum: Chordata Class: Actinopterygii Order: Perciformes Family: Cichlidae Subfamily: Pseudocrenilabrinae Tribe: Tilapiini
Genera
Oreochromis (over 30 species) Sarotherodon (over ten species) Tilapia (over 40 species) and see text

Tilapia (pronounced /təˌlɑpiə/) is both a genus of fishes in the Cichlidae family and the common name for nearly a hundred species of freshwater and some brackish water cichlid fishes belonging to the three genera Tilapia, Sarotherodon, and Oreochromis. Members of the Tilapia genus are commonly known as speckled tilapias and comprise about 42 species (ITIS 2004a), while members of the 37 species of Oreochromis are commonly known as blue tilapias (ITIS 2004b), and members of the ten species of Sarotherodon are commonly known as brushtooth tilapias (ITIS 2004c). They are native to Africa and the Middle East.

Tilapia have historically been of major importance in artisanal fishing (small scale commercial or subsistence fishing) in Africa and the Levant, and are of increasing importance in aquaculture and commercial fishing around the world. Indeed, adaptations that have benefited the survival and reproduction of tilapia—fast growing, large size, and a noted ability to become sexually mature at a young age and small size—combined with a desirable taste, also have led tilapia to become one of the most important fish in aquaculture. However, where tilapia have been deliberately or accidentally introduced, they have frequently become problematic invasive species.

Description

As members of the Cichlidae family of ray-finned fish, tilapias are characterized by a single nostril on each side of the head, an interrupted lateral line, and no subocular shelf (Nelson 2006). Tilapias comprise three genera: Tilapia, Sarotherodon, and Oreochromis (Nelson 2006; Chapman 1992). These three genera are placed together in the tilapiine cichlid tribe.

Tilapias inhabit a variety of fresh and, less commonly, brackish water habitats from shallow streams and ponds through to rivers, lakes, and estuaries. Although cichlids are found in freshwater and occasionally brackish water environments in Africa, Madagascar, Israel, Syria, India, Sri Lanka, South America, Central America, North America (one native species), and West Indies (Nelson 2006), true tilapias are native only to Africa and the Middle East (Chapman 1992). However, introduced species of tilapias are established in many environments, including several states in the United States (Chapman 1992).

Diet, reproduction, and life cycle

Most tilapias are omnivorous with a preference for soft aquatic vegetation and detritus.

The type of parental care helps to distinguish the genera of tilapias. Members of the genera Oreochromis and Sarotherodon are mouthbreeders (Chapman 1992), whereby usually the female carries the fertilized eggs and newly hatched eggs in the mouth, offering incubation and protection (Nelson 2006). Mouthbrooders normally are polygamous (Nelson 2006). After the female has released the eggs and they are fertilized, the females (typically) pick up the eggs from the nests and incubates and protects in their mouths (Chapman 1992). Species of Oreochromis in particular have mouth-brooding where only the females incubate and protect the young in their mouths (Chapman 1992). Other tilapias, belonging to the genus Tilapia, are normally substrate brooders, which incubate the eggs in a nest on the lake or pond bottom (Chapman 1992; Nelson 2006). Substrate brooders are usually monogamous and both parents may care for the eggs (Nelson 2006), including fanning water through the nests to incubate the embryos (Chapman 1992).

Tilapias are notable for being able to become sexually mature at a small size (eight to ten centimeters or three to four inches) and a young age (two to three months old) (Chapman 1992). They live six to eight years or more, including up to age 11 or 12 (Chapman 1992).

Terminology

The common name tilapia is based on the name of the cichlid genus Tilapia, which is itself a latinisation of thiape, the Tswana word for "fish" (Chapman 1992). The genus name and term was first introduced by Scottish zoologist Andrew Smith in 1840.

As they have been introduced globally for human consumption, tilapia often have specific names for them in various languages and dialects. Certain species of tilapia are sometimes called "St. Peter's fish." This term is taken from the account in the Christian Bible about the apostle Peter catching a fish that carried a shekel coin in its mouth. However, no species of fish is named in that passage of the Bible (Matthew 17:24−27). While that name is also applied to Zeus faber, a marine fish not found in the area, one tilapia (Sarotherodon galilaeus galilaeus) is known to be found in Sea of Galilee where the account took place. This particular species is known to have been the target of small-scale artisanal fisheries in the area for thousands of years (Baker 1988; Rosencrans 2003).

In some Asian countries, including the Philippines, large tilapia are often referred to as pla-pla while their smaller brethren are still referred to as tilapia (FAO 1993). In Kenya, the tilapia found in Lake Victoria (Sango), is referred to as Ngege by the Luo. Its export to the European market has threatened its availability to the Luos who consider it a staple food.

Aquaculture

Raising of tilapias for food consumption is believed to first have taken place about 2,500 years ago (Chapman 1992). Tilapia today has become the third most important fish in aquaculture after carps and salmonids, with production reaching 1,505,804 metric tons in 2002 (Fessehaye 2006).

Because of their large size, rapid growth, and palatability, a number of species of Oreochromis, Sarotherodon, and Tilapia are at the focus of major aquaculture efforts. Like other large fish, they are a good source of protein and a popular target for artisanal and commercial fisheries. Originally, the majority of such fisheries were in Africa, but accidental and deliberate introductions of tilapia into freshwater lakes in Asia have led to outdoor aquaculturing projects in countries with a tropical climate such as Papua New Guinea, the Philippines, and Indonesia. In temperate zone localities, tilapiine farming operations require energy to warm the water to the tropical temperatures these fish require. One method involves warming the water using waste heat from factories and power stations.

Tilapiines are among the easiest and most profitable fish to farm. This is due to their omnivorous diet, mode of reproduction (the fry do not pass through a planktonic phase), tolerance of high stocking density, and rapid growth. In some regions the fish can be put out in the rice fields when rice is planted, and will have grown to edible size (12–15 cm, five to six inches) when the rice is ready for harvest.

Commercial species of tilapia of particular importance include the Java or Mozambique tilapia (Oreochromis mossambicus; synonym Tilapia mossambica), blue tilapai (O. aureaus; syn. Tilapia aurea), Zanzibar or Wami tilaopia (O. hornorum; syn. Tilapia urolepis), Nile tilapia (O. niloticus; syn. Tilapia nilotica), and redbelly tilapia (O. zilli; syn. Tilapia zilli) (Chapman 1992).

Non-indigenous populations

Tilapia have been used as biological controls for certain aquatic plant problems. They prefer a floating aquatic plant, duckweed (Lemna sp.) but also consume some filamentous alga. In Kenya, tilapia were introduced to control mosquitoes which were causing malaria. They consume mosquito larvae, consequently reducing the numbers of adult female mosquitoes, the vector of the disease (Petr 2000). These benefits are, however, frequently outweighed by the negative aspects of tilapia as invasive species.

Aquaria

The larger tilapias are generally not viewed as good community aquarium fish because they eat plants and tend to be very disruptive, digging up the substrate and fighting with other fish. The smaller west African species, such as Tilapia joka, and those species from the crater lakes of Cameroon are, by contrast, relatively popular. Conversely, in cichlid aquariums, tilapias can be mixed well with non-territorial cichlids, armoured catfish, tinfoil barbs, garpike, and other robust but peaceful fish. Some species, including Tilapia buttikoferi, Tilapia rendalli, Tilapia joka, and the brackish-water Sarotherodon melanotheron melanotheron, are attractively patterned and decorative fish.

References

ISBN links support NWE through referral fees

• Baker, J. 1988. Simply Fish. London: Faber & Faber. ISBN 0571149669.
• Chapman, F. A. 1992. Culture of hybrid tilapia: A reference profile. Circular 1051 University of Florida, Institute of Food and Agricultural Sciences. Retrieved June 18, 2008.
• Fessehaye, Y. 2006. Natural Mating in Nile Tilapia (Oreochromis niloticus L.): Implications for Reproductive Success, Inbreeding and Cannibalism Wageningen: Wageningen Universiteit. ISBN 9085045401. Retrieved June 18, 2008.
• Food and Agriculture Organization of the United Nations (FAO), Fishery Information, Data and Statistics Service. 1993. Aquaculture production (1985-1991). FAO Fisheries Circular 815.
• Integrated Taxonomic Information System (ITIS). 2004a. Tilapia Smith, 1840 ITIS Taxonomic Serial No.: 169809. Retrieved June 18, 2008.
• Integrated Taxonomic Information System (ITIS). 2004b. Oreochromis Günther, 1889 ITIS Taxonomic Serial No.: 170014. Retrieved June 18, 2008.
• Integrated Taxonomic Information System (ITIS). 2004c. Sarotherodon Rüppell, 1852 ITIS Taxonomic Serial No.: 553244. Retrieved June 18, 2008.
• Nelson, J. S. 2006. Fishes of the World, 4th edition. Hoboken, NJ: John Wiley and Sons. ISBN 0471250317.
• Petr, T. 2000. Interactions between fish and aquatic macrophytes in inland waters. A review. FAO Fisheries Technical Papers 396.
• Rosencrans, J. 2003. Tilapia is a farmed fish of biblical fame The Cincinnati Post July 16, 2003. Retrieved June 18, 2008.
• Trewavas, E. 1983. Tilapiine Fishes of the genera Sarotherodon, Oreochromis and Danakilia. London: British Museum (Natural History). ISBN 0565008781.

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