Crucian Carp (Carassius auratus gibelio)The Crucian Carp is one of the two subtypes of the gold characin or goldfish (Carassius auratus). The body is covered with scales that easily detach. The Crucian Carp has a set of gullet teeth at the end of the mouth. The approximate body length is up to 30 cm, the body volume can be up to 1 kg. Exceptional catches of Crucian Carp have been recorded, being 50 cm long and weighing 2 kg. The lifespan of the Crucian Carp is about 8 years (average-aged fish).
The most suitable life conditions for the Crucian Carp are lower and middle flows of larger rivers, warmer reservoirs, and fishponds with warm water. It can bear organically polluted water, high temperatures, and large concentrations of oxygen in the water. The Crucian Carp lives in shoals. Since it has easily adapted to our waters, this has enabled it to take control over other habitats. It is considered an invasive species, because it suppresses other indigenous fish species.
The Crucian Carp is an omnivore. It feeds on zoo benthos (animals from the bottom of the water), insects, detritus (sediment), seeds and plant parts.
Female triploid (mutants) populations prevail in our waters. They reproduce gyno-genetically (incomplete fertilization where the spermatozoids only activate ovaries to divide, but there is no mergence or unification between the nuclei of ovary and semen cells). The milt of other fish (carp, characin, tench, bream, roach and European chub) activates their laid eggs. Once again, triploid fertile females are created, not bastards. The Crucian Carp spawns in May and June at the temperature of 16 to 18 oC. The young fish develop in the first or second year of life. Females lay their eggs once or twice in the spawning season within an interval of 10 to 20 days. This type of fish is a phytophagous species (lays eggs on plants) and can occasionally be an indifferent species too (capable of laying eggs on any surface). Absolute female fertility varies from 10.000 to 100.000 eggs.
The Crucian Carp is used in trade as a consume fish in our areas, but at a low market price, compared to other species. This species is not bred in fish farming, but is brought to the market exclusively as a fish caught in the nature.
There is no legal protection of the Crucian Carp in the Republic of Croatia. It is an invasive species in our waters, which is why traditional fishing and sport angling catch quotas in Kopački rit do not restrict the amount of Crucian Carp catches.
Pike (Esox lucius)The pike's body is torpedo-shaped. The dorsal and anal fins are arranged characteristically in the back part of the body, close to the caudal fin. This kind of fin arrangement is important for the pike because it enables him to accelerate rapidly while attacking his prey. The pike has very sharp teeth arranged in several rows on the lower part of the jaw. The teeth on the upper jaw are smaller and are closely arranged. The pike also has teeth in the mouth and even on the bones of the gill arcs. All together, the pike has about 700 teeth. He also has large eyes and sharp sight. The body is covered with scales.
The body length can grow up to 150 cm, whilst the average body volume is about 24 kg. The biggest catch weighed 65 kg. The pike's lifespan is about 25 years (long-aged fish).
The pike lives in calm slow-flowing or stagnant waters rich in aquatic plants from where he prowls his prey. The pike gets his bearings with his sharp sight, and ambushes his prey as quick as lightning. He is most active in autumn, throughout the day, but in summer usually early in the morning and in the evening. Sometimes he even hunts in winter during sunny days. The pike belongs to the most adjustable species of freshwater fish because he can bear extreme water temperature variations, organically polluted water, and low concentrations of oxygen.
The pike is a carnivore and a typical predator. The young fish feed on zooplanktons and zoo benthos (animals from the bottom of the water) and start hunting other fish at the size of 5 cm. The pike hunts almost all types of fish above the bottom of the water. Cannibalism has been noticed among specimens of the same size. Having the status of a predator in the food chain, the pike regulates the natural water balance by controlling the quantity of certain species like the bleak, bream, characin and others.
The pike spawns in the first months of spring at the temperature of 7 to 9 oC. Eggs are laid in flooded and flowing waters and on weedy terrains. The spawning is single. The males in our area become sexually mature in the first year, whereas the females do so in the second or third year. Absolute female fertility varies from 8.000 to 120.000 eggs.
The pike is a valuable and consumable fish. In our area, he has been traditionally bred as a secondary species in carp fishponds. His market price is high, thus he is welcome as a catch in traditional and commercial fishing. This type of fish is also very popular in sport angling. Since he is aggressive and greedy, he himself becomes easy prey for anglers.
There is no legal protection of the pike in the Republic of Croatia, but the catch quotas are restricted in traditional fishing and sport angling.
European Common Carp (Cyprinus carpio)The carp is economically the most important freshwater fish in Europe. The original wild species (from the Black Sea, Sea of Azov, Caspian Sea and Aral Sea) has a laterally compressed body, moderately elongated and covered with large cycloid scales. The snout is blunt; the mouth is large with two pairs of short barbells. The color is dark on back and golden on the sides. The belly, pectorals and pelvic are light yellow, the ventral fin is orange and the caudal fin is grey with orange shade. Coloration changes depend on habitat.
The carp is a strong fish up to one meter long or even more and can weigh 20 kg (sometimes over 30 kg). It grows very fast in the first year but later can weigh less than ordinary carps. This type of fish reaches sexual maturity at the age of 3 or 4 – males are mature one year earlier. They spawn in May and June in shallow waters with a lot of vegetation at the temperature of 15°C. Their spawning is very loud and they often jump high out of the water. The eggs are attached to the vegetation and the incubation period last for five days. Then the young ones hatch at the temperature of 20°C (approximately three). They are 5mm long and cannot stay attached to the vegetation. When old enough, they feed independently on small organisms and later on larger zooplanktons. By the time they are 2 cm long, they are eating animals from the bottom of the water. Feeding depends on the water temperature. Carps stop eating in autumn, move to deeper parts of the water and become inactive. The European Common Carp lives in deep but still waters; in rivers and stagnant waters; in armbands and basins. Their diet consists of large aquatic insect larvae, mollusks, scales, worms etc. Plants are also very important for their diet. The carp usually goes hunting in the evening or at night.