Common carp - Cyprinus carpio
(Linnaeus, 1758) [Cyprinidae]
FAO official common names: Fr - Carpe commune; Es - Carpa
Taxonomic and biological features:
Common carp belongs to the Class Osteichthyes (the bony fishes), the Order Cypriniformes and the Family Cyprinidae. In everyday life, commercial, artisanal and sport fishers use the short scientific name Cyprinus carpio in their publications.
According to different authors (e.g. Jhingran and Pullin, 1985; Pintér, 1989; Kuznetsov, Aminova and Kuliev, 2011), scientists have identified four subspecies of common carp. These are as follows:
- Cyprinus carpio carpio – European Transcaucasian common carp (from the Danube River basin in the natural waters up to the Ural Mountain range)
- Cyprinus carpio aralensis – Aral common carp (Central Asia)
- Cyprinus carpio haematopterus – Amur common carp (Amur River basin to southern China)
- Cyprinus carpio viridiviolaceus – North Vietnamese common carp.
In contrast, Balon (1995) mentions only two subspecies, C. carpio carpio and C. carpio haematopterus, while Froese and Pauly (2011) do not recognize any subspecies of common carp. Common carp is one of the most variable freshwater fish species with regard to the body shape (Figure 1).
Figure 1. Cyprinus carpio, wild and golden morphotypes (Source: FAO SIDP)
The body of native forms and improved strains may vary from elongated to deep oval. There are two basic forms of common carp: Cyprinus carpio morpha hungaricus and C. carpio morpha acuminatus. The first has an elongated torpedo-like body, while the body of the second is short and stocky, with a high shoulder (Pintér, 1989). These basic forms are presented by Balon (1995) as typical wild common carp and a feral form from the Danube delta. There are four basic types of scaliness: scaly carp, mirror carp, linear carp (also called frame carp) and leather carp (Figure 2, from upper left to bottom right). The transitional forms are the strongly or slightly-scaled irregular mirror or scattered carp (Pintér, 1989; Bakos and Gorda, 2001). Body shapes of the different forms and strains are described by the profile, head and width indexes. The profile index is the ratio of body length to body height, the head index is the ratio of body length to head length, while the width index is the ratio of body height to body width (Figure 3).
The colour of the body varies from gray through silver to bronze with a yellowish or reddish belly.
Common carp has one long dorsal fin which possesses 2–3 hard and 17–22 soft rays. The first (largest) hard ray is sharp and is serrated on its posterior margin. Additional morphological characteristics include 2–3 anal spines, 5–6 anal rays and 36–37 vertebrae (Froese and Pauly, 2011).
The mouth is large and opens in an accordion-like fashion. There are two pairs of barbels, one pair on the upper lip and the other pair at the corners of the mouth. There are 5–5 molar-like pharyngeal teeth serving to grind the food.
Common carp occur within the temperature range of 3–35 oC (Froese and Pauly, 2011). The optimum water temperature for growth and propagation is 20–25 oC. In nature, common carp live in the middle and lower sections of rivers and in areas where the water is shallow (only a few meters deep) and the bottom is muddy.
Common carp has been introduced into practically all countries where there is a chance for successful reproduction. In many of the natural waters where it has been introduced, the common carp is considered as an invasive species whose populations should be reduced or even eliminated. Still, common carp is one of the most widely cultured freshwater fish species in the world (Welcomme, 1988; Hasan at al., 2007; FIGIS, 2011).
Aquaculture production of common carp increases parallel to the increase of global aquaculture production of freshwater fishes. According to FAO (FIGIS, 2013), production of freshwater fishes was 31 839 573 tonnes in 2005, and increased to 45 335 385 tonnes by 2011 (an increase of more than 42 percent). During these years, the contribution of common carp to the global aquaculture production remained at about 8–9 percent (Figure 4).
Reproduction:
Within its native geographical range, common carp spawns from late spring until early summer in repeated occasions. In subtropical and tropical climates, common carp may have two or even three spawning periods annually which are linked to the start of the rainy season and floods.
Group mating occurs at dawn in shallow water areas covered with aquatic weeds or with freshly flooded grass. Fertilized eggs stick to the spawning substrate where they develop within a few (3–5) days or about 70 D (D indicate “day degree” which is the sum of the daily average temperature of water in which fertilized eggs or hatched larvae develop. It is used for expressing the length of incubation of eggs and rearing of fish larvae). The non-feeding larval stage lasts for the same period of time before the larvae start to swim and feed. Although the developing young fish become less and less fragile, they are extremely vulnerable to predators.
Although fully developed females release many hundreds of thousands of eggs and fertilization is usually very successful, in nature the survival of developing eggs and hatched larvae is relatively poor, thus only about 1 percent of fertilized eggs grow to sexually mature adults.
Over many centuries, the development of well-documented propagation techniques for common carp took place. This includes natural propagation, semi-artificial propagation and artificial propagation (Huet, 1972; Woynarovich and Horváth, 1980; Horvath, Tamás and Coche, 1985a).
Natural propagation
The most frequently followed techniques are:
- Prior to the breeding season, smaller (1–2 ha) shallow, grassy ponds are kept dry. When the propagation season arrives, these ponds are prepared and filled with water into which 3–4 females and 2–3 males are stocked for spawning. Later in the autumn, both fingerlings and brood fish are captured.
- According to the "Dubisch method", brood fish are stocked to spawn into small (0.01–0.1 ha) ponds. After spawning, they are immediately captured; therefore, the remaining progeny has a better chance for survival. When advanced fry are large enough, they are harvested.
In order to ensure synchronized spawning, natural or artificial hormones are used. Pituitary of carps preserved with acetone or in alcohol is the most widely used source of natural hormones, but HCG (human chorionic gonadotropin) is also used for this purpose in the Indian subcontinent. Analogues of GnRH (gonadotropin-releasing hormone) combined with dopamine inhibitor and portioned in small carp pituitary gland-like balls are those artificial hormones which are widely traded under different brand names such as OVUDAL or Ovopel. These products are increasingly used for inducing spawning/ovulation in carps worldwide.
In the subtropics and tropics, if well-prepared common carp brooders are stocked into a pond promptly inundated with freshwater, mating will very likely occur if a suitable spawning substrate can be found by the matured fish.
Semi-artificial propagation
Techniques used for the semi-artificial propagation of common carp are:
- Stripping and fertilization of eggs of ovulating females captured on the spawning ground. The fertilized eggs and hatched non-feeding larvae are incubated under controlled hatchery conditions.
- Induced spawning of brood fish kept in small ponds or "hapa". The eggs are released on natural or artificial substrates (man-made mating nests (also called “kakabans”), water hyacinth, netting material, etc.) which after spawning are taken into the hatchery for incubation.
Artificial propagation
Artificial propagation of common carp includes both the management of broodstock (establishment and maintenance of broodstock) and all steps of hatchery operation. These steps are: inducing ovulation in females with hormone injections, stripping (Figure 5), fertilization and incubation of eggs, as well as rearing of hatched non-feeding and feeding larvae (Figure 6).
Introduction to the culture of common carp
Discounting the production of advanced fry, this species is typically reared in ponds in polyculture with other fish species. Polyculture in ponds can be extensive (300–800 kg/ha/season), semi-intensive (1 000–2 000 kg/ha/season) or intensive (2 000–3 000 kg/ha/season or greater). Advanced fry are also reared in ponds but are typically raised in monoculture.
The type and number of different species and the proportion of common carp within the polyculture system vary according to the climate and the suitability, availability and marketability of other native or introduced fish species. Consequently, common carp is widely reared with Chinese major carps (silver, bighead, grass and black carps), Indian major carps (catla, rohu and mrigal), tilapia (Oreochromis spp.), South American major characids (tambaqui, pirapitinga and pacu) and with different predator fishes.
The proportion of common carp within the polyculture can be as high as 90 percent but can also be very low, only a few percent of the stocked fish. The highest stocking ratios are essentially monoculture.
The mass production of advanced fry in tanks using collected zooplankton and balanced feed is the intensive technique which is likely to become financially viable in the near future.
Although technically possible, common carp is rarely produced commercially in tanks or cages. Tacon (2001) reported that only about 3 percent of cyprinids are produced in intensive systems. Woynarovich et al. (2011) found that there are still no statistical data or published information which contradicts this statement. The relatively low price of common carp, the lack of steady availability of collectable protein-rich organisms (worms, snails, clams, insects, etc.) and the high price of fully balanced fish feeds are the main factors sustaining the dominance of semi-intensive (e.g. pond fish culture) systems. However, as soon as intensive cage and tank-culture systems for producing common carp become profitable, these culture systems will rapidly spread. This prediction is supported by the Japanese experience where intensive culture of common carp developed in the 1960s and peaked in 1997 with a yearly total production of 30 000 tonnes. Later (by 2001), the yearly production reduced to two thirds because of the diversification of people’s food preferences, product availability and depressed prices (Ikuta and Yamaguchi, 2005).