Cyprinus carpio, (L.)

Taxonomic description of species

Body compressed laterally, moderately elongate, covered with large cycloid scales. Snout blunt, mouth large, inferior. Two pairs of short barbels. Color: dark on back, golden on sides. Belly, pectorals and pelvics - light-yellow, ventral fin orange, caudal fin gray with orange shade. Coloration changes dependent on habitat. Pharyngeal teeth arranged in three rows 1�1�3-3�1�1. Lateral line scales 34-40(41), vertebrae 36-37 (23+13-14). D III-IV 16-22, its origin anterior to pelvic origin. A III 5(6). Gill rakers (27)30-33(34).
Intraspecific forms. The species is subdivided into four subspecies, of which Cyprinus carpio carpio Linnaeus, 1758 (European common carp) inhabits fresh and brackish waters of the North, Baltic, Mediterranean, Black, Azov, Caspian and Aral Sea basins, Issyk-Kul Lake; Cyprinus carpio haematopterus Temminck et Schlegel, 1846 (Amur carp) has a natural habitat extending from the Amur River basin to South China.
Four forms of the common carp Cyprinus carpio are differentiated in the Caspian Sea: Volga, Ural, Kura, Atrek (Turkmenian). They occur in the same rivers and their estuaries.
Related forms: Cyprinus carpio aralensis Spitshakow � Aral common carp; Cyprinus carpio morpha hungaricus Heck. - Hungarian common carp

Distribution of species within the Caspian Sea

Cyprinus carpio in the North Caspian inhabits the delta and delta-front of the Volga and Ural Rivers, shallow areas of the western and eastern coasts.
The species occurs sporadically in the areas from Sulak estuary to Apsheron. The South Caspian stock is dispersed through Turkmenian and Iranian waters. Along the Azerbaijani coast of the Caspian Sea occurs most abundantly in the Kyzylagach Bay and Kura estuary.
Status as per International Red Data Book: N/A
Status as per National Red Data Books: N/A
First record for the Caspian Sea: Pallas, 1814
Redescription of species: Bogutskaya, 1998

General characteristics of species

Ecologo-taxonomic group. Nektobenthos (Reimers, 1988)
Origin. Representative of early tertiary freshwater faunistic complex, Ponto-Caspian autochthonous species. The initial area of dissemination is supposed to be the Danube River basin (Misik, 1958).
World distribution. The present range of Cyprinus carpio in Eurasia is restricted approximately within latitude 35-500 North, longitude 30-1350 East (Wolny, 1974). The natural range of the species is composed of two regions: 1) water bodies of the Ponto-Caspian-Aral basin; 2) basins of the Far East rivers and rivers of south-eastern Asia, from the Amur River in the north to Yunnan (South China) and Burma in the south (Bogutskaya, 1998).
Habitat. Cyprinus carpio prefers water bodies with stagnant and slowly flowing waters. Its aggregations are confined to biocenoses with sand and/ or silt bottoms with shell incorporations.
Migrations. Cyprinus carpio does not undertake lengthy migrations but there are distinctive spawning and autumn hibernating migrations (in semi-anadromous form) 100-150 km upstream the Volga and Ural Rivers (Yanovsky, 1967). The shallow-bay form performs migrations within shallow bays and freshened estuarine areas.

Relation to abiotic environmental factors

Relation to salinity. Brackishwater euryhaline species
Relation to temperature. Eurythermic warm-water species
Cyprinus carpio feeds at temperature above 8-10⁰C, reproduces, as a rule, at temperature above 15⁰C.
Vertical distribution. Distribution within the North Caspian is restricted generally to 5 m-depth curve, also occurs at depths 10-20 m, seldom 40 m.
Relation to oxygen conditions. The species is tolerant to hypoxia, but winter oxygen deficit (fish kills) is disastrous to fish hibernating in the depressions of the Ural and Volga Rivers.
Relation to fluctuations of the sea level. The rise in sea water level (1978 - mid-1980-s) resulted in the expansion of feeding and spawning areas, and by 1985 the biomass of common carp reached 27.1 thousand tons. Further rise in sea water level (increased depths, reduced vegetation, intensified flow) practically stopped its spawning in the delta-front. The population abundance decreased and at present the commercial stock is estimated as 10.2 thousand tons.

Feeding

Feeding type. Heterotrophic
Feeding behavior. Active search, burrows in silt.
Food spectrum. Euryphagous species; consumes zooplankton, vegetable and animal detritus, zoobenthos, macrophytes. The food spectrum changes with age depending on food supply in a water body. Young fish (6.5-78 mm TL) feed on plankton (Cladocera, Copepoda, Rotatoria, Moina), overgrowing, colonial green algae, larvae of Chironomidae, etc (Vasnetsov, 1957). Adults (30-86 cm TL) feed more on mollusks and aquatic plants. 
Food supply. Unlimited. Caspian and riverine macrozoobenthos: mollusks, worms, crustaceans, larvae of insects, algae, seeds of plants.
Quantitative characteristics of feeding. N/A

Reproduction

Reproduction type. Gamogenesis
Reproduction areas. The major spawning sites of Cyprinus carpio are located in the delta, lower reaches of the Volga-Akhtuba floodplain and insular zone of the delta-front (Koblitskaya, 1977). In the south-eastern part of the sea it reproduces in the lower reaches of the Atrek River. Currently, its spawning in Azerbaijani waters occurs mainly in the Malyi Kyzylagach Bay, freshened areas of the Kirov Bay, in the outlet canal and Kura River area of the Caspian Sea.
Terms of reproduction. Spawning in the Volga and Ural Rivers begins in late April and lasts throughout May at water temperature 15-22⁰C. Because of intermittent / batch spawning, the breeding season may last for some 60-70 days. Common carp in the Atrek River spawns from mid-March (at 12-14⁰C) until early April. 
The spawning season in the Malyi Kyzylagach Bay and Kura River starts in early March with a peak in late March-early April and ends in late May.
Fecundity. The absolute fecundity of Cyprinus carpio in the Volga River varies within 145, 000 - 1,500, 000 eggs (Vysheslavtseva, 1956). Maximum fecundity is 2,100, 000 eggs. Fecundity of semi-anadromous common carp in the Ural River varies from 288,000 to 1,673,000 eggs, in the Kyzylagach population - 30,000-635,000 eggs. The Kura common carp 71-80 cm TL produces an average of 650,000 eggs, 51-60 cm TL - 363,000 eggs, 41-50 cm TL - 196,000 eggs. Fecundity of common carp in the Atrek River varies from 16,000 to 543,000 eggs, 125,000 eggs on average ( 1971-1975).
Limiting factors

Abiotic:

• The Volga River - duration of the flood period; delay of spawning temperatures.
• The Kura River - the volume of runoff, fluctuation of water level in marine shallow bays, tides, water temperature; salinity and oxygen concentration.
• The Atrek River - water discharges.

Biotic:

• abundance of breeders at the spawning grounds and their characteristics, predation.

Life history and development

Life history stages

• Prelarvae, 4.5-5.5 mm TL.
• Larvae, 7-8 mm TL.
• Developed larvae, 18-19 mm TL.
• Fry, 20 mm TL.
• Underyearlings, 20.0 cm TL.

Relation to environmental factors. Early stages (embryos, larvae and fry) are most vulnerable to pollution, fluctuations of temperature, oxygen concentration, salinity and other factors as well as to predation. As the weight of fry increases from 8.6 to 658 g, the oxygen threshold decreases from 1.25 to 0.6 mg O2 /g/h (Kuznetsova, 1956).
The top value of optimum salinity for eggs and embryos of common carp in the Kura River is 6.0�. The optimum and tolerant salinity values for larvae and fry are less 12� (Olifan, 1941).
Age of maturity. Single females in the Volga and Ural Rivers reach sexual maturity at the age of 3 years old, mean length - 36.3 cm, weight - 1.1 kg. Most females mature at the age of 4 years, mean length - 39.1 cm, weight - 1.3 kg. Single males mature at 2 years old, mass maturation occurs at the age of 3 years old . Semi-anadromous common carp in water bodies of Azerbaijan becomes mature mainly at the age of 3-4 years. Mature two-year-old fish occur in the lakes of the lower Kura River drainage and Malyi Kyzylagach Bay.
Thermal conditions of development. By the beginning of spawning season in the Volga River delta, the water temperature reaches 13-15⁰C in the river, 18-20⁰C - in low floodplains. The incubation of common carp eggs lasts 3-8 days depending on temperature.
The incubation period in the Ural River delta lasts 5 days at water temperature 15⁰C and 3 days at 20⁰C (Fish of Kazakhstan, 1988).
Spawning in the Kura River delta begins at 18-19⁰C, mass spawning occurs in April at water temperature 20-26⁰C.
The spawning season in the lower reaches of the Atrek River begins at water temperature of 12-14⁰C
Quantitative characteristics of growth. Cyprinus carpio harvested in the Volga River varies in age from 3 to 15 years, in length - 39.3-85.0 cm, and in weight - 1.4-13.3 kg.

Mean length (L) and weight (P) of the Volga common carp in even age groups. (1996-1997 - spring, 1998-2000 - spring, autumn)

Common carp from the Ural River catches is aged 3-8 years, 9.8-51.7 cm TL.

Qualitative characteristics of the spawning population of common carp in the Ural River

Comparison of growth rates of Cyprinus carpio from various parts of the Caspian Sea (Kyzylagach, Agrakhan and Turkmenian Bays) shows that four-year-old Agrakhan common carp grows faster than common carp from the South Caspian population. Growth rates of five-year old fish from these regions are almost equal; in the following years the South Caspian population considerably exceeds the Agrakhan population in growth rate

Changes in length, weight and condition factor of common carp with respect to age and habitat

Structural and functional population characteristics

Sex ratio. Sex ratio is close to 1:1.
Age-size structure. The maximum age of Cyprinus carpio in the Volga River is 16 years, the maximum length - 91 cm, maximum weight - 14 kg. The minimum legal size is 40 cm; 5-9 year old fish dominate the commercial catch.

Age composition of common carp in catches (Astrakhan Region), %

The legal size of the common carp in the Ural River varies from 40 to 100 cm (50 cm on average), weight ranges from 0.4 to 2.0 kg (up to 2.5 kg). Maximum age is 14 years, mean age - 3-6 yeas. Common carp harvested from the South Caspian (Kyzylagach Bay) varies in age from 2 to 7 years, basic age groups are 3-4 year-olds. Common carp taken from the South Caspian varies from 25 to 67 cm TL, 0.4-5.8 kg in weight .
Quantitative characteristics. In recent years, the commercial stock of Cyprinus carpio (estimated upon removal of catches in the Astrakhan Region) was assessed within 9,000 to 12,200 tons.

Abundance of common carp generations (adjusted to harvests in the Astrakhan Region), thousand tons

Common carp abundance in the Ural River and its estuary was estimated as 38,186 individuals in 1999, commercial stock - 2,500 tons.
Population trends. The abundance of Cyprinus carpio generations in the Volga River varies considerably due to natural and anthropogenic impacts. A rise in sea water level, which began in 1978, did not affect breeding conditions for common carp initially, but by the mid-1980-s because of changes in spawning habitats, reproduction areas shifted from the delta-front to the upper reaches of the delta and the lower part of the Volga-Akhtuba floodplain. Altered conditions of spawning caused a gradual decline in the biomass of common carp population, which is presently estimated as 10,200 tons.
Abundance in the Ural River also varies considerably because of unstable conditions of reproduction. In general, the stock of common carp is in decline there.

Interspecific relations

Cyprinus carpio is a food competitor with regard to the other benthos-feeding fish. Common carp in itself (especially, young fish) is a food item for predators (catfish, sturgeons, seal).

Importance of species to bioresources production of the Caspian Sea

Economic significance of species. A commercially important species. Cyprinus carpio is reared at fish breeding hatcheries and pond fish farms.
Commercial characteristics of species, catches. Catches in Russian waters vary from 2.600 to 3.600 tons, in the Ural River - from 80 to 700 tons.

Harvest trends for common carp in the Volga � Caspian region, thousand tons

Catches of common carp in Turkmenian waters did not exceed 460 tons. Catches in Azerbaijani waters in 1989 and 1990 were 300 and 100 tons, respectively.
Fishing gears and fishing zones. Common carp is taken from Russian waters by beach seines, fyke nets, fixed nets, and drag nets.
The major fishing grounds are located in lower reaches and delta-front of the Volga River, shallow water areas at the western coast of the North Caspian.
Common carp in the Ural River and its estuary is caught using beach seines, hoop nets and fixed nets.

Impact of fisheries on the population status

At present, the range of commercially exploited population of the Volga common carp is located in the delta-front and freshened areas of the North Caspian. Following fishery rules (introduced in 1984), harvesting common carp and other semi-anadromous fish in the protection zone in front of the river mouth was limited.
Large catches of common carp in the Ural-Caspian region were recorded before 1951 when fishing was conducted mostly at sea. Commercial fishing pressure in the river and sea resulted in destruction of common carp stocks. By 1964, the catch of common carp from the sea decreased to 300-900 centners and did not exceed 300-500 tons in the river. A ban on common carp fishing at sea promoted its population recovery.
Human impact/Threats. Under conditions of regulated river flow, the main factors affecting reproduction are hydrometeorological conditions of flooding (see Limiting factors).
Conservation measures. For the Volga-Caspian common carp:

1. Adjustment of water releases/ discharges for fisheries purposes.
2. Reclamation of spawning sites.
3. Increase in the production of young fish at fish breeding farms.
4. Reinforcement of protective measures.

For the Ural-Caspian common carp:

1. Reclamation of the floodplains and delta of the Ural River.
2. Construction of 2-3 fish breeding farms in the Ural River. Pond culture development.
3. Reinforcement of protective measures.
4. Reduction in pollution of the Ural River and estuarine zone.

In order to recover and increase the abundance of common carp population in the Caspian-Atrek region, it is necessary to maintain stable flooding of spawning sites and enhance access of mature fish to the spawning grounds. Sustainable fishery is needed as overfishing adversely affects reproduction and stocks of common carp.
Stock abundance in the Kura-Caspian area is maintained by restocking efforts of hatcheries and fish breeding farms (Ust-Kura and Kyzylagach fish farms). These efforts need to be increased through reconstruction and building of new breeding farms in Azerbaijan.

References

Bogutskaya, N.G. 1998. Annotated catalogue of Cyclostomata and fish inhabiting continental waters of Russia. Nauka. Moscow. 220 p.(in Russian)
Fish of Kazakhstan, 1988. Nauka. Alma-Aty. P.p. 231-279 (in Russian).
Koblityskaya, A.F. 1977. Succession of spawning communities in the Volga River delta. Vopr. Ichthyol.J. Vol.17, 4(105): 607-620 (in Russian).
Olifan, V.I. 1941. Influence of salinity on eggs and larvae of Caspian common carp, roach and bream. VNIRO Proceedings, 16: 159-172. Food Industry. Moscow-Leningrad (in Russian).
Vysheslavtseva, T.V. 1956. Observations of the development of common carp reproductive products in the Volga River delta. VNIRO Proceedings, 32: 99-107 (in Russian).
Yanovsky, E.G. 1967. On the biology of common carp in the Ural RiverIn: Biological principles of the fisheries in Middle Asia and Kazakhstan. Balkhash. Pp. 319-. 320.

Compiled by:

Yu.A. Kuznetsov (CaspNIRKh, Astrakhan, Russia)
I.M. Aminova (KazNIIRKh Atyrau Branch, Atyrau, Kazakhstan)
Z. M. Kuliev (AzerNIRKh, Azerbaijan)