Common carp

The common carp (Cyprinus carpio), also known as European carp, Eurasian carp, or simply carp, is a widespread freshwater fish of eutrophic waters in lakes and large rivers in Europe and Asia. The native wild populations are considered vulnerable to extinction by the International Union for Conservation of Nature (IUCN), but the species has also been domesticated and introduced (see aquaculture) into environments worldwide, and is often considered a destructive invasive species, being included in the list of the world's 100 worst invasive species. It gives its name to the carp family, Cyprinidae.

The type subspecies is Cyprinus carpio carpio, native to much of Europe (notably the Danube and Volga Rivers).

The subspecies Cyprinus carpio haematopterus (Amur carp), native to eastern Asia, was recognized in the past, but recent authorities treat it as a separate species under the name Cyprinus rubrofuscus. The common carp and various Asian relatives in their pure forms can be separated by meristics and also differ in genetics, but they are able to interbreed. Common carp can also interbreed with the goldfish (Carassius auratus); the result is called Kollar carp. Another artificial hybrid is ghost carp, which is bred between common carp and Japanese Purachina koi. The large variations of colours produced make ghost carp a popular commercial species.

The common carp is native to Europe and Asia, and has been introduced to every part of the world except the poles. They are the third-most frequently introduced fish species worldwide, and their history as a farmed fish dates back to Roman times. Carp are used as food in many areas, but are also regarded as a pest in several regions due to their ability to out-compete native fish stocks. The original common carp was found in the inland delta of the Danube River about 2000 years ago and was torpedo-shaped and golden-yellow in colour. It had two pairs of barbels and a mesh-like scale pattern. Although this fish was initially kept as an exploited captive, it was later maintained in large, specially built ponds by the Romans in south-central Europe (verified by the discovery of common carp remains in excavated settlements in the Danube Delta area). As aquaculture became a profitable branch of agriculture, efforts were made to farm the animals, and the culture systems soon included spawning and growing ponds. The common carp's native range also extends to the Black Sea, Caspian Sea, and Aral Sea.^{[citation needed]}

Both European and Asian subspecies have been domesticated. In Europe, domestication of carp as food fish was spread by monks between the 13th and 16th centuries. The wild forms of carp had already reached the delta of the Rhine in the 12th century, probably with some human help. Variants that have arisen with domestication include the mirror carp, with large, mirror-like scales (linear mirror – scaleless except for a row of large scales that run along the lateral line; originating in Germany), the leather carp (virtually unscaled except near dorsal fin), and the fully scaled carp. Koi carp (錦鯉 (nishikigoi) in Japanese, 鯉魚 (pinyin: lĭ yú) in Chinese) is a domesticated ornamental variety that originated in the Niigata region of Japan in the 1820s, but its parent species is likely the East Asian carp, possibly C. rubrofuscus.

The carp has a robust build, with a dark gold sheen that is most prominent on its head. Its body is adorned with large, conspicuous scales that are very shiny. It has large pectoral fins and a tapering dorsal fin running down the last two-thirds of its body, getting progressively higher as it nears the carp's head. Its caudal and anal fins may either be a dark bronze or washed with a rubbery orange hue. Two or three spines are on the anal fin, the first being serrated, and the dorsal fin has three or four anterior spines, the first of which is also serrated. The mouth of the carp is downward-turned, with two pairs of barbels, one pair at the corners of the upper lip, and the other on the lower. Wild common carp are typically slimmer than domesticated forms, with body length about four times body height, red flesh, and a forward-protruding mouth. Common carp can grow to very large sizes if given adequate space and nutrients. Their average growth rate by weight is about half the growth rate of domesticated carp. They do not reach the lengths and weights of domesticated carp, which (range, 3.2–4.8 times) can grow to a maximum length of 120 centimetres (47 in), a maximum weight of over 40 kilograms (88 lb). The longest-lived common carp documented was of wild-origin (in non-native habitat of North America), and was 64 years of age. The largest recorded carp, caught by British angler, Colin Smith, in 2013 at Etang La Saussaie Fishery, France, weighed 45.59 kilograms (100.5 lb). The average size of the common carp is around 40–80 cm (16–31 inches) and 2–14 kg (4.4–30.9 lb).^{[citation needed]}

Although tolerant of most conditions, common carp prefer large bodies of slow or standing water and soft, vegetative sediments. As schooling fish, they prefer to be in groups of five or more. They naturally live in temperate climates in fresh or slightly brackish water with a pH of 6.5–9.0 and salinity up to about 0.5%, and temperatures of 3 to 35 °C (37–95 °F). The ideal temperature is 23 to 30 °C (73–86 °F), with spawning beginning at 17 to 18 °C (63–64 °F); they easily survive winter in a frozen-over pond, as long as some free water remains below the ice. Carp are able to tolerate water with very low oxygen levels, by gulping air at the surface.

Common carp are omnivorous. They can eat a herbivorous diet of aquatic plants, plant tubers, and seeds, but prefer to scavenge the bottom for insects, crustaceans (including zooplankton and crawfish), molluscs, benthic worms, fish eggs, and fish remains. Common carp feed throughout the day, with the most intensive feeding at night and around sunrise.