Key Points of Artificial Breeding Technology in Black Carp Aquaculture

The black carp is an excellent species for freshwater aquaculture in our country. It uses benthic organisms as feed, grows quickly, has a large individual size, tender flesh, and good flavor, and is high in fat and protein with abundant vitamin content, making it highly valued by the public and professional aquaculture households. The demand for fry is increasing day by day, and the prospects for carrying out artificial breeding of black carp are broad.

Cultivation of Black Carp Broodstock

The black carp broodstock cultivated by the author came from original stock in the Yangtze River waters. Black carp broodstock aged 6 years or more, weighing over 15 kg, robust in constitution, uninjured, with females and males at a 1:1 ratio, were selected for holding. The holding pond area is 3 mu-7 mu, with a water depth of over 2 m, a flat pond bottom, and loam soil. The black carp broodstock were polycultured in grass carp and black carp ponds for cultivation at 1 fish-2 fish per mu, and one month before induced spawning the black carp were concentrated in a dedicated pond for cultivation. Feeding was mainly with fresh snails and mussel meat, supplemented with a small amount of rapeseed cake and soybean cake feed. Water should be flushed regularly; generally once a month in winter, once every 5 days-7 days each month after the beginning of spring, and once every 3 days-5 days in the month before spawning, to promote gonadal development of the black carp broodstock.

Induced Spawning

1. The induced spawning period is mid-to-late May, at a water temperature of 22℃-30℃, with 25℃ being most suitable.

2. Selection of black carp. The maturity of black carp directly affects the induced spawning result, so black carp should be strictly selected when pairing for induced spawning. The selection standard for males is that gentle pressure on the abdomen causes semen to flow from the genital pore and disperse after being placed 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. Types, doses and injection methods of spawning agents. Commonly used drugs for induced spawning of black carp include “PG” (pituitary), “LRH-A” (luteinizing hormone-releasing hormone analog), “HCG” (human chorionic gonadotropin), “GTH” (gonadotropin), and “DOM” (domperidone). Usually a mixture of 3 kinds-4 kinds of drugs gives a better induced spawning effect. The two-injection method is used for induced spawning with relatively high effectiveness; the doses are: for females, the first injection of LRH-A at 2 mg-5 mg per kg, and after an interval of 8 hours-12 hours, a second injection at a dose of LRH-A 10 mg-20 mg + PG 2 mg-4 mg + HCG 500 IU-1200 IU, or additionally DOM 5 mg. These are prepared as a mixed agent and injected intraperitoneally. The injection dose for males is 1/3-1/2 of the female dose. The effect time is 8 hours-10 hours.

Estrus and Artificial Insemination

After the second injection of the spawning agent, the black carp broodstock are returned to the spawning pond. When the effect time is reached and the black carp show estrus, artificial egg collection and fertilization should be carried out promptly. The length of the effect time varies with the water temperature; at 25℃-28℃, the effect time is 8 hours-10 hours. At this time, carefully observe the estrous behavior of the black carp: when the estrus time of the black carp arrives, catch the black carp, place them properly in a fish carrying clamp, and examine them. 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 stripped of semen that rapidly disperses on its own in warm water, then artificial egg collection and semen collection can begin, carrying out dry artificial fertilization. If natural eggs and sperm cannot be collected, return the black carp broodstock to the spawning pond and wait for the black carp to show estrus. The collected eggs and sperm should be fully mixed to achieve fertilization. When performing artificial insemination, avoid direct sunlight, which can kill the eggs.

After insemination, the fertilized eggs should be quickly diluted with water and placed into the circular channel for incubation. Before artificial insemination, preparations should be made for personnel, tools, washbasins, nets, fish beds, brushes, etc. Personnel should coordinate and cooperate well, and movements should be light and quick to avoid injuring the black carp broodstock.

Circular Channel Incubation

The artificially collected fertilized eggs should be promptly placed into the prepared circular channel with flowing water for incubation, at a density not exceeding 1.2 million eggs per sq m. The flow velocity in the circular channel should be appropriate. In the early stage, the water flow velocity is about 17 cm/sec, sufficient to lift the swollen fertilized eggs tumbling up to the water surface. When the fry have just hatched out of the membrane, management should be strengthened to prevent fish eggs from sticking to the circular channel filter cloth and to prevent water flow issues, so the water flow velocity should be increased (30 cm/sec); at the same time, prevent fish from sinking or sticking to the filter cloth and suffocating to death. After the fry show the waist spot, the water flow velocity should be reduced to avoid consuming the fry's energy. Eight hours after the waist spot appears, the fry can be boxed 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.

Disease Prevention and Control

Before artificial breeding work begins, the induced spawning and incubation tools, drugs, etc. should be prepared. At the same time, the fry disease prevention and control policy of “prevention first, prevention more important than treatment” should be adhered to, namely microscopic examination. If black carp fry become diseased, the appropriate medicine can be used to promptly and thoroughly kill the disease and pests, thereby increasing the survival rate of black carp broodstock fry.

In summary, the main experiences are: first, cultivate the black carp well to promote good gonadal maturity; second, strictly select black carp with qualified standard maturity for induced spawning; third, use highly effective mixed spawning agents for induced spawning; fourth, use artificial insemination for egg collection and fertilization; fifth, strengthen incubation management to increase the hatching rate and fry survival rate.