Common carp, Cyprinus carpio (Linnaeus, 1758) belongs to Cyprinidae family. It is a freshwater species and but present in brackish water also. It is distributed around the world. The length at first maturity measures 34.9 cm and ranges from 25 - 36 cm. Adults inhabit in warm, deep, slow-flowing and still waters.
Common carp is hardy in nature and can tolerate a wide variety of conditions. It usually favours large water bodies with slow-flowing or standing water with soft bottom sediments. Both the adults and juveniles feed on the different benthic organisms and plant material. Adults often undertake considerable spawning migration to suitable backwaters and flooded meadows. Larvae survive in warm water especially shallow submerged vegetation area.
The IUCN Red List Status has listed the common carp under the "vulnerable" category.
An appropriate selection of broodstock is very important to obtain better results in breeding and grow-out. The fish characteristics such as the largest, recorded fastest growth with desired body shape are considered for selection of brood fish. It is not advisable to choose the brood fish from the same brood fish or offspring as it results in inbreeding depression. It further leads to poor growth performance and preponderance of deformed fry.
Two to three year old brood fishes (weighing about 2 – 3 kg) are suggested for ideal breeding. They can be used for several years, as the larger sized fishes spawns more and larger number of eggs than smaller fishes. About 1 – 1.5 lakhs eggs are produced per kg of body weight of fish.
Three to four month before to the breeding season, the brood fishes are detached and stocked in segregated ponds to avoid the unwanted spawning. Secondary sexual characters distinguish the male and female fishes. Female have swollen abdomen due to developing ovaries and in the male, the milt ooze out when the abdomen is gently pressed towards the genital pore. The segregated brood fishes are not to be maintained in crowded condition. They are to fed protein rich artificial diet for the fast gonadal development. High carbohydrate feeds are to be avoided to prevent the deposition of fat. Avoiding stress through netting is required.
Artificially stimulation propagation
Common carp breed naturally in confined water. Several methods of propagation have been developed in different areas. Pond spawning is easier when the farmer does not have hatchery. It is possible to spawn common carp in cement cistern or hapa and later the fertilized eggs or the larvae can be transferred into the nursery-rearing tank.
The selected brood fishes are introduced into the hapa without any administrated dose at the ratio of two male and one female. Spawning take place within 24 – 36 hours. A better fecundity and good spawning response is noticed when the flow is maintained with new water. Fibre is commonly used to collect the fertilized eggs, due to adhesive nature of the egg. The collected eggs are shifted to another hapa. After three days, the newly hatched fry are transferred into the nursery-rearing tank.
Artificial propagation by hormone by stripping method
When the condition is not favourable for successful natural spawning or there is a requirement for production of greater amount of fry, the Hypophysation technique is to be used to induce the fishes. The induced spawning and rearing of larvae provide a greater control in hatchery when compared to the natural propagation, besides ensuring better survival rate when fry is reared in indoor condition.
The brood fishes are selected from the segregated ponds and are directly used for breeding. The response to propagation is less in Female fishes and hence it is advisable to inject double the number required. The number of males to be injected will be about two-third of the number of female injected. The dose and sequence of injection is not standardized and practices vary considerably. The administered dose (ovatide) is 0.2 to 0.3 ml/kg of fish for male and for the female it is 0.4 – 0.5ml/kg of body weight of fish. The dose is injected intramuscularly between the base of dorsal fin and above the lateral line. The administered male and female fishes are kept separately. Before stripping, the fishes are anesthetized using ethyl –M-aminobenzoate at 100 ppm (bath for 3 – 5 minutes) to avoid the handling difficulties. The female fish is stripped by gently squeezing the abdomen towards the anal. The eggs that flow easily are collected in a container. Similarly the male is stripped for milt which is also collected in the same container. The female release about 150,000 eggs per kg of body weight and egg measure ranges between 0.9 – 1.9 mm dia.
For a litre of eggs, two or three-litre milt is essential for better fertilization rate. The eggs and milt are properly mixed using feather as it clumps together due to adhesive nature. The sticky nature of the eggs can be addressed by using the sodium chloride and carbamide (4 g sodium and 3g carbamide dissolved in a litre of water). Initially add this solution while mixing the eggs and milt for about 5 – 10 minutes. As eggs begin to swell, a small quantity of solution is added at regular intervals. Within 1 – 1.30 hrs, the swelling of eggs is completely stopped, and the first cleavage occurs. However, to completely remove the sticky layer, the eggs are washed with the tannic acid solution (0.05 – 0.07 percent) for 20 seconds and for about 5 times. Each time 0.01 percent of water is added to the stock solution. Finally, eggs are washed in freshwater for about 5 minutes and is now ready for incubation.
The eggs are incubated in a simple double hapa. The hatching hapa consist of 2 x 2 x 1m with a fine mesh size of 0.5mm with an inner hapa made also made of the same material with a mesh size of 2.0 – 2.5 mm. The eggs are spread inside the hapa. The hatched larvae fall through the larger meshes of the inner hapa and are retained by the outer hapa. After hatching, the inner hapa with dead eggs, egg shells and other debris is removed to avoid the deterioration of water quality. The eggs are stocked inside the hapa after hatching out and they are transferred into the nursery-rearing tank.
Artificial propagation by hormone
The success rate of Hypophysation of common carp is about 60 – 70 percent. The result will be poor if the brood fishes have not been fed with sufficient protein-rich feed. The Hypophysation is done in small tank or hapa where the eggs are scattered. The submerged aquatic plants, kakaban or fibre are used as substrata for laying eggs. After three days, the newly hatched out larvae are collected from the hapa and are stocked into the nursery pond.
Nursery tanks are usually shallow and have a depth of 0.5m. The newly hatched three day old larvae are stocked at a density of a million of fry in a 20m2 cement cistern. The suggested water flow is 1 litre minute per square meter. The live food organisms are collected from the wild and are fed to them for better results in terms of survival and growth. Farmers can feed the larvae with starter feed and brine shrimp, if possible. Larvae reache 1 – 2 cm within 15 – 20 days of culture period.
For spawn rearing, the nursery ponds are usually small (0.02 – 0.05 ha) and shallow with a depth of 1 m. Seasonal ponds are preferred than perennial ponds considering the absence of aquatic weeds and weedy fishes. A three-day-old fry measure 5 – 6 mm size. It is reared for 2 – 3 weeks by when it reaches about 25 – 30 mm size. The stocking density highly varies and it ranges between 10 – 40 lakhs per hectare. When the stocking density is higher, an additional supplementary feed is essential to achieve better survival and improved growth. If it is reared in a well-prepared pond, the achievable survival rate is about 60 – 70 percent.
The pond preparation is exactly similar to Indian Major Carp.
The carps spawn are susceptible to environmental condition and food availability. Before release of the spawns, make sure congenial condition and adequate food (natural food organisms) exist to enhance the survival rate. The prepared pond environment should provide an optimum condition for spawns. The drainable or seasonal ponds are effectively prepared by draining and drying, ploughing, liming, filling with water and fertilizers. Perennial or undrainable ponds have two more steps - control of aquatic weeds and eradication of predatory and weed fishes.
Dewatering and drying of pond
The pond is dried for a minimum of 7 – 10 days (until crack on the clayey soil and in the sandy soil footprint do not form on the soil). The drying and ploughing of pond facilitate the oxidation of organic matter, degassing of hydrogen sulphide and ammonia, kills the pathogenic microorganism, predatory and weed fishes and remove the unwanted aquatic weeds.
The pond productivity depends on the soil quality of the pond, such the pH, water retention, texture, total organic carbon, available nitrogen and available phosphorus. Liming helps to improve the productivity by adjusting soil pH, mineralization of organic matter, release of soil bound phosphorus to water and disinfection of pond bottom. The agricultural lime (CaCO3), dolomite (CaMg(CO3)), calcium carbonate (Ca (OH)2), calcium oxide (Cao) can be used for application. The quantity of application varies with its effectiveness and soil pH. 200 – 500 kg/ha of lime is applied to pond soil. After application, the bottom of the pond should be ploughing to mix the surface soil. The quick lime is preferred for soil, and the agricultural lime is preferred after stocking the seeds. The optimum soil pH to be maintaind is about 6.5 to 7.0.
Poorly managed ponds are infested with emergent, floating, submerged and marginal weeds. It reduces phytoplankton production (nutrient competition, prevent light penetration), causes oxygen issue (supersaturation in day and depletion in the early morning), provides shelter to predator fish and insect, reduces the living space, increases siltation, and obstruct netting and harvesting.
The aquatic weeds can be controlled by the manual, mechanical, chemical and biological methods. The selection of method depend on the pond size, extent of weeds infestation, availability of time and cost. Manual method is advocated for weed removal because it is easier, less time consuming and cost effective.
Physical method of weed control
Chemical method of weed control
Biological method of weed control
Eradication of predatory and weed fish
The presence of predatory and weed fishes in nursery affect the survival rate. These fishes normally spawn before carp spawning and increase their population. The larvae of predatory fishes may compete with carp seeds for the food, space and oxygen, which affects the growth and survival rate. Thus, eradication of weed fishes such as the murrel, catfishes, puntius, barbas danio and anabas is necessary before stocking the carp seeds. The dewatering and drying is the best practice to remove the predatory and weed fishes. If it is not possible, pesticide application can be taken up. The selected pesticide should have the following good characters - effective at low doses, does not affect the quality of the fish, rapidly detoxifies, economical and easily available.
Certain derivatives of plant origin such as Derris root power, Mahua oilcake, Tea seed cake can be used.
Under the chemical method,
The successful fry rearing in ponds depends on the availability of zooplankton. For sustained zooplankton production availability of phytoplankton and bacterial base are important factors. Phytoplankton production requires adequate nitrogen and phosphorus. The nutrients can be added by organic and inorganic methods.
The organic manures are rich in carbon and contain a small amount of nitrogen and phosphorus. It promotes zooplankton growth by the saprophytic food chain. Cow dung and poultry manure are organic manures that are usually used. They are applied before 15 days of seed stocking at the rate of 5 – 6 tons/ha and 2 – 3 tons/ha respectively. The nitrogen and phosphorus are 2 – 3 times greater in poultry manure than cow dung manure. Hence half of the dose of cow dung is used when poultry manure is applied.
The inorganic fertilizers used are Urea or Ammonium sulphate as a source of nitrogen and Single or Triple phosphate as a source of phosphorus.
When the applied dose exceeds the limit, blue-green algae blooms. Thus, a mixed use of organic and inorganic fertilizer is recommended (750 kg groundnut or mustard oil cake, 200 kg cow dung and 50 kg of single super phosphate per hectare) for the sustained and rapid production of phytoplankton.
The fingerlings production pond is also prepared similar to the nursery pond but the insect control is not used. The cow dung (3 – 4 tons/ha) and single super phosphate (30 – 40kg/ ha) are added to the fingerling production pond before 10 days of stocking. After stocking, 500kg/ha cow dung and 10 kg/ha of single super phosphate are added twice in a month. The usage of cow dung is reduced about one-third to half when poultry manure is applied.
The fingerlings are required for larger size pond (0.05 – 0.20 ha) rather than fry. The pond depth is to be 1.5 – 2.0 m. Four crops are possible in a perennial pond but only one crop is possible in temporary ponds due to lack of sufficient water to rear the fry. The fry is reared into fingerlings, which take around 2 – 3 months. Stocking density is the factor determining the growth of fishes. Thereby, proper stocking density is essential. The stocking density of 1 lakh/ha would yield 100 mm sized fingerlings in 2 months and 150 mm in three month period with 70 – 80 percent survival. Daily supplementary feed is provided as two rations at the rate of 5 – 7 percent of the body weight. The supplementary feed include rice bran or wheat brawn mixed with groundnut oil cake / mustard oil cake / cotton seed oil cake in the ratio of 1:1. To achieve greater growth extra ingredients such soya flour, fishmeal vitamins, mineral mixture can also be included.
The grow-out pond is also prepared similar to the nursery and fingerlings pond. The fingerlings of 100 mm is considered ideal stocking size for medium sized ponds. The advanced fingerlings of size 150 mm are best for stocking in temporary ponds as they would grow faster and can be marketed within 6 – 8 months. Advanced fingerlings are suggested for stocking in larger ponds and open waters where competitor and predators are present in good number. However, normally common carp is cultured with composite fish culture along with Indian Major Carps and Chinese carps.
Food is the major factor, which determines the growth of fish. The natural food is inadequate, so supplementary feed (rice bran or wheat brawn the mixture with groundnut oil cake /mustard oilcake / cottonseed oilcake in ratio of 1:1) is required. To meet the nutritional deficiency, extra ingredients such as soya flour, fishmeal vitamins, mineral mixture can also be included. Feeding twice is preferred. Excess and under feeding should be avoided because both affect the fish growth directly. The preferred feeding rate is 3 – 5 percent of the body weight of fish. Common carp reach about 2.5 – 3.5 kg in 10 – 14 months. The average marketable size is 1.2 – 1.8 kg.
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