Fish
Common Carp
Cyprinus carpio · also called European carp, koi carp, mirror carp
The common carp is a fish humans have carried everywhere. Kept in ponds since Roman times, bred into monastery food, temple koi, and scaleless “mirror” varieties, and then stocked into rivers on six continents — where, in many of them, it has become one of the most destructive freshwater invaders on Earth.
Overview
Cyprinus carpio is native to the Danube basin and Central Asia and now established almost worldwide. It is a heavy, deep-bodied, bronze fish with two pairs of barbels, and it feeds by rooting through bottom mud, sifting out insects, seeds, and plant matter.
Two thousand years of breeding
The Romans farmed carp; medieval monasteries raised them for fast days. Selective breeding produced the mirror and leather carp, and, in 1820s Japan, the ornamental koi.
Why it damages wetlands
Constant bottom-rooting stirs up sediment, uproots plants, and releases nutrients, turning clear, weedy shallows into turbid green water and destroying the nursery habitat native fish and waterfowl rely on. In Australia’s Murray-Darling, carp are the majority of fish biomass.
A double life
In Europe and Asia the carp is a prized food and sport fish; in North America and Australia it is a pest. Meanwhile the true wild form, in its native range, is assessed as Vulnerable — squeezed by habitat loss and interbreeding with escaped domestic stock.
Common Carp: common questions
Are koi and goldfish just types of carp?
Koi are, directly. Koi are a domesticated, colour-selected form of the common carp, Cyprinus carpio, developed by rice farmers in Niigata, Japan, from the early nineteenth century by keeping and breeding the occasional brightly coloured fish that turned up in their carp ponds. A koi and a wild carp are the same species and will interbreed freely, and koi released into the wild revert toward drab carp colours within a few generations. Goldfish are a separate story — they are a domesticated form of a different fish, the Prussian or gibel carp in the genus Carassius, bred in China over a thousand years ago. So koi are carp; goldfish are close cousins of carp.
Why are carp such a problem where they have been introduced?
The damage comes from how they feed. A carp works over the bottom by taking in mouthfuls of sediment, filtering out the food, and expelling the rest, and a dense population doing this continuously keeps the water permanently cloudy, tears up rooted plants, and recycles nutrients from the mud into the water column, which fuels algal blooms. Clear, weedy shallows are the nursery habitat for most native fish and the feeding grounds for ducks and wading birds, and carp turn them into turbid, bare, green water. Because carp are so hardy and breed so heavily, once established they are extremely difficult to remove.
How big and how old do common carp get?
Commonly 40 to 80 cm and a few kilograms, but in good conditions they grow much larger, with well-documented fish over 30 kg and rod-caught records approaching 50 kg. They are long-lived, routinely reaching 20 years and sometimes 40 or more, and a few captive individuals have been claimed to be far older. Big old carp are wary and hard to catch, which is part of what makes specimen carp fishing a serious pursuit in Europe, where anglers may target a single known large fish for years.
Is "invasive carp" in the US the same as the common carp?
Usually not. The common carp has been established in North America since the 1800s and is now simply part of the fish fauna, if an unwelcome one. The term invasive carp, formerly Asian carp, refers to four more recent arrivals, the bighead, silver, grass, and black carp, which escaped from fish farms in the southern United States and have spread up the Mississippi system. The silver carp is the one that leaps out of the water when startled by boat engines. These species and the common carp are all in the carp family but are different fish with different impacts.