Key Points and Methods of Black Carp Breeding Technology Explained
The black carp is an excellent variety for freshwater aquaculture in China. It uses benthic organisms as feed, grows quickly, has a large body size, tender meat and good taste, and is high in fat and protein with abundant vitamin content. It is highly valued by the public and professional aquaculture farmers, and the demand for fry is increasing day by day, so there are broad prospects for developing artificial breeding of black carp.
Fry Rearing Methods
For black carp broodstock, choose fish aged 6 years or older, weighing more than 15 kg, with a robust constitution and no injuries, and keep females and males at a ratio of 1:1 for holding. The holding pond should have an area of 3-7 mu, a water depth of more than 2 m, a flat bottom, and loam soil, with 1-2 fish per mu. One month before induced spawning, concentrate the black carp in a dedicated pond for rearing.
Feed the black carp broodstock mainly with fresh snails and mussel meat, supplemented with a small amount of rapeseed cake and soybean cake feed. Flush with water regularly: generally once a month in winter, once every 5-7 days each month after the beginning of spring, and once every 3-5 days during the month before spawning, to promote gonadal development of the black carp broodstock.
Design of the Broodstock Rearing Pond
1. Location: The broodstock rearing pond should be selected as a pond that is sheltered from the wind and faces the sun, has an abundant and high-quality water source, has soil with strong water retention capacity, and has convenient drainage, irrigation and transportation.
2. Area: The fish pond is best rectangular, with an area of 2000-4000 sq m being suitable.
3. Water depth: The water depth is generally 1.5-2.5 m as suitable. In winter, the water level should be deepened to keep warm; in spring and summer, the water level should be lowered to raise the water temperature.
4. Water quality: The water quality should have suitable fertility, and the pond bottom should be flat.
5. Greenhouse: The temperature suitable for the growth, development and spawning of black carp is 20-30°C. Building a greenhouse broodstock pond can remove the limitation imposed by low temperature on fish gonadal development and increase the quantity and quality of broodstock spawning. When using a greenhouse, open the greenhouse windows at noon every day or use an aerator for artificial aeration, which can raise the water temperature by 5-7°C and bring dissolved oxygen to 4-5 mg/L.
Black Carp Breeding Technology
1. Spawning induction time: The spawning induction time is generally mid-to-late May, with a water temperature of 22-30°C, and 25°C being the most suitable.
2. Selection of black carp maturity: The maturity of black carp directly affects the effect of spawning induction, so black carp should be strictly selected when pairing for spawning induction. The selection standard for males is that gentle pressure on the abdomen causes semen to flow from the genital pore and disperse in warm water; for females, the better ones have a distended abdomen that is soft and elastic, with relatively sparse scales on the abdomen.
3. Use of spawning agents: Commonly used drugs for spawning induction in black carp include "PG", pituitary, "LRH-A" luteinizing hormone-releasing hormone analogue, "HCG" human chorionic gonadotropin, GTH gonadotropin, "DOM" domperidone and other spawning agents. Usually, a mixture of 3-4 drugs has a better spawning induction effect, and the two-injection method gives a higher spawning induction rate. For females, the first injection is 2-5 mg of LRH-A per kg; after an interval of 8-12 hours, inject the second dose, which is LRH-A 10-20 mg + PO 2-4 mg + HCG 500-1200 IU, or additionally DOM 5 mg, prepared into a mixed agent and administered by intraperitoneal injection. The injection dose for males is 1/3-1/2 of the female dose, and the effect time is 8-10 hours.
4. Estrus: After injecting the second dose of spawning agent, put the black carp broodstock back into the spawning pond. When the effect time is reached and the black carp shows estrus, carry out artificial egg collection and fertilization in time. The length of the effect time varies with the water temperature. At 25-28°C, the effect time is 8-10 hours. At this time, carefully observe the signs of estrus in the black carp. As soon as the estrus time of the black carp arrives, catch the black carp and place it in a fish carrier clamp for examination. At this point, if gentle pressure on the abdomen of the female causes eggs to flow out from the genital pore on their own, and the male can be squeezed to release semen that disperses rapidly in warm water, artificial egg collection can begin.
5. Semen collection: Carry out dry artificial fertilization. If natural eggs and sperm cannot be collected, put the black carp broodstock back into the spawning pond and wait for the black carp to show estrus. The collected eggs and sperm should be fully mixed to achieve fertilization. During artificial insemination, avoid direct sunlight killing the eggs. After insemination, quickly dilute the fertilized eggs with water and place them into the circular channel for incubation. Before artificial insemination, prepare personnel, tools, washbasins, nets, fish beds, brushes, etc., and coordinate personnel well so that movements are light and quick, so as to avoid injuring the black carp broodstock.
6. Circular channel incubation: The artificially collected fertilized eggs should be promptly placed into the circular channel flowing water prepared in advance for incubation, with a density not exceeding 1.2 million eggs per sq m. The flow rate in the circular channel should be appropriate. In the early stage, the water flow rate is about 17 cm/second; after swelling, the fertilized eggs should be lifted and roll up to the water surface as the standard. When the fry have just hatched from the membrane, management should be strengthened to prevent the eggs from sticking to the circular channel filter cloth and to prevent water flow problems, so the water flow rate should be increased (30 cm/second). At the same time, prevent the fish from sinking or sticking to the filter cloth and suffocating to death. After the fry show the waist spot, reduce the water flow rate to avoid consuming the fry's strength. Eight hours after the waist spot appears, the fry can be put into boxes for sale. After the fry can eat, feed them four times a day, each time one egg yolk per 100,000 fry, to strengthen the fry's constitution.