“Carp” names a crowd of cyprinids, not one fish
Carp is a common label for many freshwater cyprinid fishes, a huge Eurasian-rooted ray-finned clade prized by anglers and aquaculturists alike. They sit among Ostariophysi with catfishes and characins, sharing peculiar ear–swim-bladder links. Tribolodon alone among cyprinids truly tolerates salt water.
In everyday speech the name usually means a handful of big species: the common, crucian, grass, silver and bighead carp. The common carp is native to Eastern Europe and western Asia, hence the label Eurasian carp. Goldfish and koi, a domesticated form, made carp popular ornamentals, and that trade and the food value spread them widely. In much of the Old World they are prized; across swathes of Africa and Australia and in most American states they count as trash fish and invasive pests, and control programmes cost large sums worldwide.
Carp belong to the Ostariophysi, a mostly freshwater superorder shared with characins, catfishes and knifefishes. Its hallmark is the Weberian apparatus, small bones derived from the first five vertebrae and their ribs, which probably relays vibrations from the swim bladder to the inner ear and would explain the group's sharp hearing. Most species have scales and teeth in the throat shaped by diet. Tribolodon is the only cyprinid genus at home in salt water, though some species visit brackish water before returning to rivers to spawn.
Some carp can survive for months with almost no oxygen, under ice or in stagnant water, by turning glycogen into lactic acid and then into ethanol and carbon dioxide; the ethanol leaves through the gills.
In 1653 Izaak Walton called the carp the queen of rivers in The Compleat Angler. Britain now has a booming carp-angling scene with its own magazines and a record fish of 68 lb 1 oz. American anglers long scorned the common carp, present since the 1880s, but some state agencies and clubs now promote it as a hard-fighting sport fish.
Source: Carp
