Grass carp? No: Black carp (Mylopharyngodon piceus) breeding technology video, scientific rearing methods explained in detail
In China, black carp has traditionally been polycultured with silver carp, bighead carp and grass carp, which has become the main method of pond fish farming in China. Because it mainly feeds on snails, limited feed resources have restricted the development of black carp farming. Initial results have now been achieved using artificial compound feed. The protein content in the feed should be 28 to 41%, increased or decreased depending on the different growth stages. Black carp in their first year are prone to hemorrhagic disease, and 2-year-old fish frequently develop enteritis; sporozoosis and gill rot are also very common. Naturally growing black carp also have relatively important economic value in some areas along the middle and lower reaches of the Yangtze River.
Ecological habits
1. Feeding habits. The black carp is a carnivorous fish; at the fry and fingerling stages it mainly feeds on zooplankton. When the body length reaches about 15 cm, its feeding habit changes and it begins to feed on small snails and similar prey. As the pharyngeal teeth develop, their crushing function strengthens, and juvenile fish feed mainly on mollusks, such as mussels and river snails. In addition, they also eat shrimp, crabs and insect larvae.
2. Growth. The black carp has a large body size and grows rapidly, with a maximum weight of up to 70 kg. 1-year-old fish can grow to 500 g, 2-year-old fish to 2.5 to 3 kg, and 3-year-old fish can reach 6.5 to 7.5 kg in a good environment. The increase in body length of black carp is fastest at 1 to 2 years of age, and after 5 years of age its body length growth rate slows; weight gain is fastest at 3 to 4 years of age, and it continues to gain weight thereafter.
3. Reproduction. The black carp is a migratory fish; it grows and develops in waters connected to rivers, enters the rivers to overwinter in winter, and after the beginning of spring the overwintering brood fish swim upstream, and during the upstream migration their gonads develop rapidly to maturity; they spawn in spawning grounds in the main stream of the river, and after spawning the brood fish again enter the connected waters to fatten up. The breeding season is May to June each year, and the required water temperature is 18 to 28°C. When the spawning ground rises in water level, the current speed is 1 to 2 m/s, and the flow pattern becomes turbulent, the brood fish begin to spawn. Black carp eggs are pelagic and hatch and develop as they drift with the current. The age of sexual maturity of the black carp is: females 5 to 7 years, males 4 to 5 years. Spawning type: sexually mature individuals mature their gonads once a year and spawn once. The fecundity of the black carp increases markedly with body weight; generally, brood fish of 15 to 20 kg have a fecundity of about 600,000 to 1,000,000 eggs.
Artificial propagation
1. Sources of brood fish
Natural fry and fingerlings from river basins, or fry and fingerlings produced by state-owned original stock farms, or adult black carp selectively collected from natural germplasm resource banks, or from natural waters such as rivers, reservoirs and lakes that have not been artificially stocked, and then cultivated to serve as brood fish. Inbred offspring must not be used as a source of brood fish……
2. Brood fish cultivation
(1) Brood fish are required to be over 6 years old and weigh more than 15 kg, stocked at a female-to-male ratio of 1:1.5, with about 10 black carp of 15 to 20 kg stocked per mu.
(2) The bottom of the brood fish pond should be flat, preferably sandy loam, and the water quality should be kept fresh; feeding should mainly be river snails, clams and mussel meat, supplemented with a small amount of soybean cake and malt, with regular addition of fresh water and flushing water. Generally, in winter the water should be flushed once a month and the water depth kept at more than 2 m. After the beginning of spring, lower the water level to help raise the pond water temperature, flush water once a week, and from mid-April begin to increase the frequency of water flushing, which can be once every 2 to 3 days, to promote gonad maturation.
(3) In the brood fish pond, stock a small number of silver carp and bighead carp to regulate water quality, and at the same time appropriately stock carnivorous fish such as snakehead and California bass to prey on wild trash fish in the pond, which is beneficial to brood fish cultivation and also increases pond returns.
3. Induced spawning of brood fish
(1) Spawning induction time and water temperature. In the middle and lower reaches of the Yangtze River, the spawning induction time is mid to late May, and the most suitable water temperature for spawning induction is 25 to 28°C.
(2) Selection of brood fish. The maturity of the brood fish directly affects the effect of spawning induction. The criteria for identification are: when the abdomen of the male is gently squeezed, semen flows out and disperses immediately upon contact with water; the abdomen of the female is enlarged, soft and elastic, and the scales on the abdomen are relatively sparse. To increase the maturity of the population, a seine net check can be carried out in mid-April, and for those with poorer maturity, according to individual size and maturity, inject LRH-A 3 to 5 micrograms per fish respectively.
(3) Injection of spawning-inducing agents. Commonly used spawning-inducing agents are LRH-A, DOM, PG, etc.; usually mixing two of them gives better results. Our farm uses three injections, giving a relatively high spawning induction rate, as high as more than 95%. The first injection is 1 microgram of LRH-A per kg of body weight per brood fish, with an interval of 20 hours; the second injection is 5 micrograms of LRH-A per kg of body weight per brood fish, with an interval of 8 hours; the third injection is 20 micrograms of LTH-A plus 3 to 4 mg of PG or plus 4 to 5 mg of DOM per kg for female brood fish, and the dose for male brood fish is 1/3 to 1/2 of the dose injected into female brood fish depending on the specific situation; all injections are given by the thoracic cavity route.
4. Courtship and artificial insemination
The length of the effect time varies with the water temperature. According to observations, at a water temperature of 26 to 28°C the effect time is 6 to 7 hours. When the brood fish reach the expected time of courtship and in combination with the actual courtship condition, the brood fish are caught for artificial insemination. During insemination, care should be taken to act gently and quickly; when mixing sperm and eggs, appropriately add 0.6% physiological saline to prolong the insemination time; at the same time, during insemination direct sunlight and rainwater splashing should be avoided to improve the fertilization rate. The normal fertilization rate reaches more than 90%.
5. Hatching
Put the water-absorbed fertilized eggs into a hatching ring channel or hatching jar for hatching; the water flow rate should be such that it can lift and tumble the fertilized eggs; the hatching water should be supplied and discharged separately and should not be recirculated. After the fry hatch out of the membrane, the water flow should be appropriately increased to prevent the fry from sinking and suffocating to death; after the fry have been hatching for 24 hours, the water flow should be appropriately reduced to avoid excessive water flow consuming the fry's energy. At the same developmental stage, the water flow rate during the day is lower than at night; if the weather is abnormal and the temperature difference is large, it should be appropriately reduced to avoid excessive water flow consuming the fry's energy. At the same developmental stage, the water flow rate during the day is lower than at night; if the weather is abnormal and the temperature difference is large, the water flow should be appropriately increased.
Fish disease prevention and control
1. Strict disinfection before stocking fingerlings; after they are put into the pond, sprinkle 1 g/m3 of crystal trichlorfon over the whole pond once, then regularly disinfect with 25 ppm quicklime and 1 ppm bleaching powder, and regularly feed drugs to prevent enteritis; the feed should be fresh and palatable; dead fish should be removed promptly and buried deep in the soil, and all fishing gear used should be soaked and disinfected.
2. The main disease of black carp is enteritis. Use norfloxacin 30-50 mg/kg fish body weight/day, garlic bulb 5-10 g/kg fish body weight per day, allicin 0.5 g/kg fish body weight per day. Sulfaguanidine 50 mg/kg fish body weight per day on the first day (doubled for the first dose), used continuously for 6 days.