Physical Characteristics
The common carp has an elongated, moderately tall body that is slightly compressed laterally, with a characteristic fusiform shape that allows it to navigate efficiently through slow waters. The body is covered with cycloid scales arranged in regular rows, although there are also cultured varieties with partial scales (mirror carp) or completely lacking scales (leather carp). The head is relatively small in relation to the body, lacking scales, with a terminal or subterminal mouth equipped with thick, fleshy lips. A distinctive feature is the presence of two pairs of tactile barbels on the upper lip – one short and one longer – which help it detect food in sediments. Coloration varies from olive-green on the back to golden-yellow on the flanks and whitish-yellow on the abdomen. The fins are robust, and the dorsal fin is long, with a strong bony spine at the front, providing protection against predators.
Habitat & Distribution
The common carp prefers standing or slow-flowing waters with sandy or muddy bottoms and abundant vegetation, being a eurythermal species that tolerates temperatures between 3°C and 35°C. In the Danube Delta, its habitat includes permanent and temporary lakes, floodplain ponds along the river, channels with slow current, and confluence areas of the Danube branches. The species adapts excellently to the variable conditions of the delta, migrating seasonally between feeding and spawning areas. The common carp is a benthic species, spending most of its time near the bottom, where it searches for food by sifting through sediments with its protractile mouth apparatus. Although it prefers waters with medium oxygen content, it can also survive in environments poorer in oxygen, retreating in winter to deep areas where it enters a state of reduced activity. The wild population from the Danube is considered the most genetically valuable, representing the native European subspecies (Cyprinus carpio carpio).
Behavior and Feeding
The common carp is an omnivorous fish with an extremely varied diet, adapting its food preferences according to season and food availability. In spring and autumn it consumes predominantly animal food – aquatic insects and their larvae, crustaceans, mollusks, and worms – while in summer it tends more toward consumption of plant matter, algae, and organic debris. Its feeding method is characteristic: the fish inserts its protractile mouth into sediments, sucking up food along with mud particles, which it then filters through the mouth equipped with powerful pharyngeal teeth capable of crushing shells and snail shells. The common carp is a social fish during periods of intensive feeding, gathering in groups in areas with rich food resources. Its activity is increased early in the morning and late in the evening, especially in warm months. In autumn, before winter, the common carp consumes large amounts of food to accumulate fat reserves, a time when it becomes extremely active and offers excellent opportunities for fishermen.
Life Cycle & Reproduction
The common carp reaches sexual maturity relatively early, at 2-5 years of age, depending on environmental conditions and food availability. Reproduction occurs in spring, during April-June, when water temperature consistently exceeds 18°C. In the Danube Delta, the spawning period often coincides with spring floods, which create ideal conditions by flooding meadows with abundant vegetation. The female lays an impressive number of eggs – up to 120,000 eggs per kilogram of body weight, which means that a 10 kg female can lay over one million eggs. The eggs are sticky and attach to submerged vegetation, being fertilized externally by males spraying milt. The laying process is noisy and often violent, with males striking the female's abdomen to facilitate egg expulsion. Hatching occurs after 3-8 days, depending on water temperature. The fry initially feed on zooplankton, gradually transitioning to benthic invertebrates as they grow. The common carp can live 20-30 years under natural conditions, and isolated specimens have reached over 50 years.
Conservation Status
Although the species Cyprinus carpio is classified globally as Vulnerable (VU) by IUCN, the situation of populations varies dramatically by region. Wild populations from the Danube basin, especially the rheophilic populations from the river, are in decline due to hydrological modifications (dams, channelizations), pollution, overfishing, and hybridization with domesticated strains escaped from farms. In the Danube Delta, the common carp benefits from a certain degree of protection through biosphere reserve regulations, including spawning prohibition periods (April-June) and a legal minimum retention size of 35 cm. However, the pressure from commercial and recreational fishing remains high. Internationally, the common carp is considered an invasive species in many countries in North America, Australia, and South Africa, where it was introduced and has negatively affected local ecosystems. Conservation of native populations from Eastern Europe, including the Danube Delta, is essential for preserving the species' original genetic diversity and maintaining the ecological balance of Danubian wetlands.
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