There are currently more than 20 valid species in the genus Cyprinus, all of which native to eastern and southern Asia with the exception of C. carpio (Fricke et al. 2023). However, this diversity has not been widely recognised and some taxa, e.g., the widespread Amur Carp (C. rubrofuscus Lacepède 1803), were considered to be conspecific with C. carpio prior to their relatively recent revalidation (Kottelat 2001).

Moreover, a number of Cyprinus species have a long history of domestication, eventually leading to them being widely hybridised and translocated at the global scale (Vandeputte 2003).

As a result of these factors, both European and Asian carps plus their domesticated strains continue to be referred to collectively as C. carpio or "Common Carp" in the majority of published literature.

In addition, the nominal eastern Asian subspecies Cyprinus carpio haematopterus Temmink and Schlegel 1846 continues to be viewed as a valid taxon in some scientific literature, but is in fact a synonym of C. rubrofuscus (Kottelat 2006).

In order to maintain clarity for Red List purposes, C. carpio is referred to as 'Eurasian Carp', while the term 'Common Carp' is reserved for artificially cultivated and stocked individuals of uncertain provenance, and thus refers to the vast majority of non-native subpopulations. Both terms are used out of necessity in several sections of this assessment.

The Eurasian Carp has an extensive natural range, with large non-hybrid subpopulations remaining in the Caspian Sea basin and potentially elsewhere.

The global population, number of mature individuals, and extent of suitable habitat are estimated to be declining, but this species cannot currently be placed into any threatened category based on Red List criteria.

It is therefore assessed as Least Concern.

This species is native to most rivers draining to the Black, Azov, Caspian and Aral sea basins, and possibly northeastern Greece. It has been introduced outside of its natural range on a more or less pan-global basis alongside a number of congeneric species, particularly Amur Carp (Cyprinus rubrofuscus).

There is strong evidence to suggest that the Eurasian Carp was first introduced to the Mediterranean region centuries ago, possibly dating back to Greco-Roman times. More recently, hybrids and genetically-altered individuals have been translocated to all major continents, where they have been widely released into natural waters (see 'Use and Trade'). They are universally referred to as "Common Carp" or "Carp" despite their disparate and often uncertain ancestral origins. Neither an accurate description nor map of the Eurasian Carp's non-native range could therefore be produced within the scope of this assessment.

Common Carp are ranked among the most invasive freshwater fishes globally. In North America, Australia, and increasingly other areas outside their native ranges, they may dominate fish communities, are regarded as nuisance species, incur significant economic costs, and management efforts are directed toward control and eradication. Elsewhere, e.g., central and western Europe, United Kingdom, they are viewed as "naturalised" posing little or no threat to native aquatic communities, and continue to be extensively stocked.

This species' population status has not been quantified, and the genetic structure of the native population is poorly understood. An accurate global appraisal is complicated since it is unclear to what extent genetically-pure Eurasian Carp prevails within its natural range, given the ongoing and extensive stocking with cultured fish (see 'Threats').

Large subpopulations apparently remain in the Caspian Sea, where introductions of domestic strains have been limited, and in three small lakes of northwestern Türkiye. The conservation status in the Black, Azov and Aral sea basins is less clear, while if the species is native to northeastern Greece it appears to have been extirpated there.

An overall decline in the global population is estimated.

This comparatively large species naturally inhabits lentic and sluggish lotic habitats with relatively deep water and beds of aquatic vegetation, such as lowland river channels, floodplains and large natural lakes. It is eurytopic, and able to breed prolifically in artificial lakes, ponds, canals and irrigation ditches, while tolerating a wide range of temperatures and oxygen concentrations.

It is primarily an omnivorous benthivore, feeding on aquatic invertebrates and other zoobenthos by sucking in mouthfuls of sediment and ejecting the unsuitable material. Organic detritus and plant material are also consumed, including the stalks, leaves and seeds of both aquatic and terrestrial vegetation. Its foraging activity typically drives nutrient release from the substrate, and in a well-functioning ecosystem this can enhance phytoplankton productivity, accelerate nutrient fluxes and benefit organisms occupying higher trophic levels, including other fish species.

However, if the biomass of adult Eurasian or common carp individuals reaches a critical threshold for a given aquatic system there can be serious adverse effects, leading to significant changes in ecosystem community structure and an overall loss of biodiversity. Submerged aquatic vegetation may be uprooted or consumed, inorganic and organic solids from the sediment resuspended, and the fish can excrete large quantities of nutrients into the water column, which can drive deleterious shifts in phytoplankton production and community structure. Such consequences are typically evident in the conversion of shallow, clear-water, macrophyte-dominated lakes and ponds to turbid, unvegetated habitats with increased eutrophication rates. These degraded habitat conditions negatively affact the abundance and richness of native fishes, especially sight predators, thus driving homogeneity in fish communities. In addition, there exists experimental evidence that carp-dominated water bodies are considerably less attractive to waterfowl and other wetland birds.

Research had also demonstrated that Cyprinus species can play a significant role in driving biodiversity loss through predation of fish and amphibian eggs and larvae, dragonfly and other aquatic invertebrate larvae. This suggests that they occupy a dual position in terms of lake and pond community structuring, acting both as bottom-up ecosystem engineers and top-down predators. When present in sufficient numbers, they are therefore likely to induce dramatic biodiversity decline independent of the advancement of the eutrophication process or prior to ecosystem shift to a turbid state.

The Eurasian Carp is long-lived and can reach at least 50 years of age. Within the native range male individuals attain sexual maturity between 3-5 years of age, and females between 4-6 years. Spawning occurs in late spring (usually May-June, when water temperatures reach 17-18°C) along shallow shorelines, backwaters and in floodplains, and adults may migrate considerable distances in search of suitable habitat. It is a highly fecund, fractional (i.e., females release batches of eggs at intervals during the reproductive period) spawner, and fully-mature females can release as many as 2,000,000 eggs per year. These are deposited among dense vegetation, with individual females typically pursued by several males which compete to fertilise them. Upon contact with water, the eggs become adhesive and swell 3-4 times in volume. Hatched fry initially stick to the substrate until their yolk sacs are absorbed, and remain in warm, shallow, marginal habitats during the initial growth period.

It is important to note that much of the available information regarding the biology of Eurasian Carp is based on studies of feral populations comprising domesticated fish. The ancestral wild phenotype possesses a more elongate overall shape than the typically deep-bodied domestic strains, and may be more specialised in terms of habitat requirements and other aspects of life history. For example, in the Black and Caspian Sea basins there is evidence that some subpopulations are semi-anadromous, with adults inhabiting brackish water and migrating from the sea to adjacent rivers or coastal areas to spawn. These traits could feasibly render non-hybrid wild subpopulations more susceptible to anthropogenic habitat modification.

This species is threatened by genetic introgression with introduced domestic Common Carp strains, which appear to be ubiquitous throughout much of its native range. Uncontrolled and sometimes illegal restocking with these strains continues in many areas, where the rate of hybridisation with wild subpopulation is likely to be high.

Extensive habitat modification has also occurred throughout the Eurasian Carp's range. In particular, damming of lowland river channels has blocked annual migration routes, while canalisation and floodplain drainage has reduced the extent of available spawning grounds (see 'Habitats and Ecology').

The combined effect of these threats on the global Eurasian Carp population has not been investigated in detail, although a number of authors have commented on their potentially adverse nature.

Cyprinus species were probably the first freshwater fishes exploited for aquaculture. Evidence from China dates back to c. 6,000 BC, while in Europe the Eurasian Carp has been cultured for at least 2,000 years. Today, they rank among the most commercially-important freshwater food fishes with global fishery and aquaculture production increasing by 35% to c. 3.9 million tonnes in the ten years from 2009-2019 according to FAO data. Aquaculture provides more than 95% of this volume, and Common Carp production occurs in more than 80 countries. China is the largest supplier, producing more than 70% of the global total, while in some European countries (e.g., Czech Republic, Poland), Common Carp account for more than 80% of total fish production.

As a result of this widespread, long-term exploitation, a number of domesticated strains of Common Carp were developed due to contrasting aquaculture management strategies in different geographical regions. These include three with reduced scale cover, commonly referred to as 'mirror' (scattered scales), 'linear' (with a single row of scales along the side of the body), and 'leather' (entirely scaleless) carp, respectively.

A number of classic methods have been used in attempts to increase productivity and breeding efficiency, including hybridisation, crossbreeding, chromosomal manipulation and selective breeding. Targeted traits have included improved growth rates, manipulation of body shape, and resistance to cold or disease, with varying degrees of success, while genetic techniques have focussed on artificial sex regulation, production of genetically sterile offspring and gene transfer. The majority of global production is still carried out using unselected strains, however, and where they do exist organised programmes are based mostly on crossbreeding. Research has revealed low genetic diversity in domesticated strains compared with wild subpopulations.

Domesticated strains of Common Carp have been translocated internationally since at least the 18^th century, and this process expanded intensively during the 20^th century. In numerous cases this has been followed by their subsequent release or escape into natural waters, including within the native range of the Eurasian Carp (see 'Threats').

In addition to their aquaculture value, Common Carp are also prized as sport fish with a high socioeconomic value, particularly in Europe and the United Kingdom, but also North America, Africa, and increasingly elsewhere. In some countries carp fishing represents an important branch of tourism and can provide alternative income pathways for commercially-managed fisheries. An international industry based on specialised tackle and techniques to catch large carp for recreational purposes has developed since the mid-20^th century. Where Common Carp have been stocked for angling purposes, they consist entirely of domesticated strains and are often repeatedly restocked using fish from a range of sources.

Contrary to popular understanding, the Eurasian Carp is not the parent species of the ornamental Koi (aka nishikigoi) Carp, which comprises a series of selectively-bred colour forms of the Amur Carp.

This species is not protected at the international scale, and no coordinated conservation management plan exists.

In Croatia it is currently assessed as Endangered at the national level, and further stocking of domestic Common Carp strains is illegal throughout the country.

Some authors have suggested that refuge populations using genetically-pure fish from known locations should be established. To that end, field surveys designed to establish precisely where non-hybrid subpopulations remain are recommended as a priority measure.