Seed supply
Spawning on nests, aquatic weeds and inundated grass in tanks and ponds
Carp may spawn throughout the year in tropical areas of India, with peaks in January-March and July-August. Breeding is carried out in hapas, cement tanks or small ponds. Submerged aquatic plants are used as substrata for egg laying. When the fry are 4 to 5 days old, they are stocked into nursery ponds.
The 'Sundanese method' is used for spawning carp in Indonesia. The broodfish are kept in broodfish ponds, segregated by sex. Matured broodfish are transferred to 25-30 m² spawning ponds. 'Kakabans' (nests made of the fibre of
Arenga species) are installed into the ponds. The fish lay their eggs on both sides of the kakabans. When spawning is completed, the nests are transferred to hatching/nursing ponds.
Small ponds are used for spawning carp in China. Aquatic weeds (
Ceratophyllum, Myriophyllum) or floating palm leaves are used as spawning substrata.
Small 'Dubits ponds' (120-300 m² water surface area) were used for spawning, and for short nursing of carp fry in Europe in the past. More recently, ponds with an area from a few hundred m² up to 10-30 ha are used here. Two to four weeks after spawning, the fry can either be harvested from these large ponds, or may remain there up for rearing to fingerling size.
Hatchery based seed production
This is the most effective and reliable method of seed production. Broodfish are kept in water saturated with oxygen, within the temperature range of 20-24 ºC. They are given two doses of pituitary gland injection, or a mixture of GnRH/dopamine antagonist, to induce ovulation and spermiation. The eggs are fertilized (applying the 'dry method') and the adhesiveness of the eggs is eliminated using salt/urea treatment, followed by a tannin acid bath (the 'Woynarovich method'). Incubation is carried out in Zoug jars. The hatched fry are kept in large conical tanks for 1 to 3 days, and are usually stocked at the stage of 'swim-up' or 'feeding fry' into properly prepared ponds. Approximately 300 000 to 800 000 newly hatched fry can be expected from a single female.
Nursery
Nursing of common carp in ponds and tanks
Shallow, aquatic weed-free drainable ponds of 0.5 to 1.0 ha are the most suitable for carp nursing. Nursery ponds must be prepared before stocking to encourage the development of a rotifer population, since this constitutes the first food of feeding fry. The stocking density is 100-400 fry/m². The ponds should be inoculated with
Moina or
Daphnia after stocking. Supplementary feeds, such as soybean meal, cereals meals, meat meal, or mixtures of these materials, should be applied. Rice bran or rice polishings can also be used for feeding fry. The length of the nursery period is 3 to 4 weeks. The final fish weight is 0.2-0.5 g. The survival rate is 40-70 percent.
If there are many predators in the area where ponds would be situated (insects, snakes, frogs, birds, wild fish), tank nursing of carp can be applied. Tanks of 5-100 m² surface area, made of concrete, bricks or plastic, can be used for nursing fry up to 1-2 cm in size. By applying hay and manure, dense populations of
Paramecium and rotifers can be established in these tanks. A few hundred fry per m² can be stocked. Collected zooplankton and fine particle size meals, or complete starter foods can be used. Industrial type systems, such as raceways, or water recirculating systems are also suitable for nursing.
Fingerling production
The production of carp fingerlings normally takes place in semi-intensive ponds, based on manure/fertilizer-generated natural food and supplementary feeding. Fingerling production can be carried out in a single stage system (stocking newly hatched fry and harvesting fingerlings), a dual stage system (stocking nursed fry and harvesting fingerlings), or a multicycle system (when newly hatched fry are stocked, and the fish are thinned out several times).
Stocking nursed fry is the most effective way for producing medium and large size fingerlings. Depending on the required final size of fingerlings, 50 000-200 000 nursed fry/ha can be stocked in temperate zones, preferably in polycultural systems where the proportion of common carp is 20-50 percent. The final weight of the carp is 30-100 g. In warm climates, if large size fingerlings are the production target, the stocking density of nursed fry is 50 000-70 000/ha, out of which the proportion of common carp is 20 percent. Survival rates of 40-50 percent are achieved. Small size fingerlings can be produced in ponds stocked with 400 000 small (15 mm) nursed fry. In this case the survival rate is 25-30 percent.
Frequent application of manure is necessary to maintain the plankton population. The feeding is based mainly on agricultural by-products in subtropical areas, on cereals and/or pellets in temperate zones.
Ongrowing techniques
Production of two summer-old carps
In temperate zones, one-summer old fish (20-100 g) must be reared up to 250-400 g in the second year. The stocking rate is 4 000-6 000/ha, plus about 3 000 Chinese carp/ha, if only cereals are fed. The stocking rate can be much higher (up to 20 000/ha) if cereals and pellets also used. The daily ration is approximately 3-5 percent of body weight.
Production of market size fish
Common carp can be produced in extensive, natural food and supplementary feed-based monocultural production systems, in stagnant water ponds. Artificial feed-based intensive monocultural production can be carried out in cages, irrigation reservoirs, and running water ponds and tanks, or in recirculation systems.
Common carp are stocked with Chinese carps, and/or Indian major carps, tilapia, mullet, etc., in polycultural systems. This constitutes a natural food and supplementary feed-based production method, in which fish that have different feeding habits and occupy different trophic niches are stocked into the same ponds. The quantity of fish should be in accordance with the productivity of natural food organisms. The frequent application of manure or fertilizers and the proper species ratio, make the maintenance of productive populations of natural food organisms, and the maximal utilization of the productivity of pond ecosystem possible. Synergetic effects between fish species support the production in polycultural ponds.
Carp culture can be integrated with animal husbandry and/or plant production. Integration can be direct (animals above fish ponds), indirect (wastes of animals are used in the ponds as manure), parallel (rice-cum-fish), or sequential (fish production between crops). The sequential cycling of fish/animal/legumes/rice (in 7 to 9 year cycles) is suitable for significantly decreasing the environmental loading of intensive aquaculture/agriculture. Since common carp burrow in the pond bottom, have a broad environmental tolerance and an omnivorous feeding habit, they are a key species in integrated systems.
Common carp can also be stocked into natural waters, reservoirs, and temporarily inundated areas, in order to utilize the natural food production of these waters for enhanced capture fisheries. In this case the fish stocked should be 13-15 cm fingerlings produced in fish farms ('aquaculture-based fisheries') in order to avoid the losses that would occur with smaller fish. Common carp are usually stocked with other cyprinid species, in accordance with the productivity of the water and the intensity of exploitation.
Feed supply
The use of natural food has been mentioned in other sections of this fact sheet. These are sometimes supplemented with compounded farm-made or commercial feeds.
Harvesting techniques
Undrainable ponds, or drainable ponds with a long harvesting ditch, or ponds with inner or outer harvesting pits are used for carp rearing. The fish are usually harvested by seine nets. The length of nets should be 1.5 times the width of ponds, but not longer than 120-150 m.
In undrainable ponds, selective harvesting can be done. The maximum weight of carp which can get through various mesh size nets are: 20 mm mesh size = 20 g fish; 25 mm = 40 g; 30 mm =100 g; 35 mm =170 g; 40 mm = 270 g; 50 mm = 400 g.
Since the carp keep mud-free the area where they search for food, feeding should be done throughout the growing period in the harvest area. At harvest time the water should be drained slowly (1-3 days from a 1 ha pond, 8-14 days from 30-60 ha ponds). The fish gather in the deepest area of the pond, unless they are frightened away by an abrupt decrease of water level, or by noises. Since carp tend to swim towards incoming water, a small quantity of water is flowed into the pond near the drainage site to concentrate the fish, especially if the water temperature is high. When a large quantity of fish is concentrated in the harvesting pits aeration should be supplied. Sprinkling water on the surface is usually not sufficient.
Partial harvesting (regardless whether the ponds are drainable or undrainable) increases the total production of the ponds by improving the conditions for the remaining population.
Handling and processing
If harvesting is carried out in warm water, the fish are pre-conditioned by repeated stressing before netting. Harvested fish can be transferred live in aerated tanks for 3-5 hours, if the fish/water ratio is not more than 1:2. The density of fish in transport tanks and the duration of transport depend on fish size, temperature and the amount of aeration.
If, during harvesting, fish have been enticed into the harvesting area by feed, only very short transport time is feasible, since the oxygen demand of satiated fish is high.
The majority of carps is transferred live to markets, and is sold either live or freshly dressed. Successful trials have been carried out on the large scale filleting of carp in France. Apart from value-added products, about 15 different products can be prepared from carp, representing different levels of processing.
Production costs
The average profit of carp production in some Hungarian fish farms was EUR 326/ha (from sales of EUR 1 652/ha) between 1999-2001, according to a survey by the Research Institute of Fisheries, Aquaculture and Irrigation (unpublished data). In India the net profit from polyculture, in which common carp represented 25 percent of the total fish stocked, was reported to be USD 710/ha (from sales of USD 1 929) in 1990 (Sinha,1990). The profit of small scale farmers in Bangladesh was reported to be USD 510-1 580/ha (from sales of USD 1 540-2 610/ha) from undrainable polyculture ponds, in which the stocking ratio of carp was 20 percent (Gupta
et al., 1999).