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 an invasive species, being included in the list of the world's 100 worst invasive species. It gives its name to the carp family, Cyprinidae.
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.
Common carp are benthic feeders and root in sediment for food items. Their barbels may help to feel for food embedded in the sediment, like plant tubers or annelids. Carp pick up sediment by generating suction and mouth the content to identify and select food items by taste and size. Gill rakers form a branchial sieve that may aid in food separation, but the carp is also able to clamp down on food items it detects using a muscular palatal pad and inferior postlingual organ. The sediment is passed back and forth between the mouth and pharynx repeatedly as food is found. The carp may end up spitting out sediment, which contributes to water turbidity.
While common carp have no oral teeth, 10 pharyngeal teeth are used for crushing or grinding food. The carp has no stomach, and the intestinal length can vary based partially on dietary composition in early life.
