How can the survival rate of artificially bred black carp be improved?

The maturation period of black carp is later than that of silver carp, bighead carp and grass carp broodstock, and the gonads generally struggle to reach the standard for induced spawning at the end of stage IV. Therefore, a method of promoting maturation should be adopted. 15 to 20 days before induced spawning, seine the pond to check the maturity of the broodstock, and promptly give the less mature female and male broodstock 1 to 3 maturation-promoting treatments. Among maturation-promoting hormones, LRH—A3 gives the best results, with the dose controlled at 0.1-0.2 micrograms per kilogram of broodstock body weight.

Choose a broodstock rearing pond with a quiet surrounding environment and no disturbance, with a water depth of more than 1.5 m. Black carp are stocked together in grass carp broodstock ponds, at 1-2 groups per mu of water surface, and are not polycultured with common carp; the feed is mainly live river snails, supplemented with a small amount of concentrated feed; the water quality should remain fresh and pollution-free, with sufficient oxygen and a transparency of more than 35 cm. The broodstock rearing pond should preferably maintain a continuous slight flow of water over the long term, and 1 month before induced spawning the flow speed should be gradually increased to stimulate the broodstock and promote gonadal development, so that the broodstock reaches maturity.

Keep the water clean, non-toxic and sufficiently oxygenated. Prevent predators from entering the circular channel and harming the eggs and fry, and use 80-100 mesh copper sieve silk to filter the incubation water. Adjust the incubation water flow rate well: before hatching and after membrane dissolution, control the flow rate at 0.25 m-0.3 m/s, and adjust it to 0.3 m-0.5 m/s during membrane dissolution. Frequently wash the filter sand screens to prevent the screens from clogging and avoid the loss of eggs and fry.

Select female broodstock that are uninjured, robust in constitution, with a soft and elastic abdomen, a slightly red, relaxed and slightly protruding genital pore, an abdomen that feels liquid-like when touched by hand, and eggs developed to the end of stage IV, and male broodstock that release milky white semen when the abdomen near the genital pore is gently pressed, with the semen dispersing immediately upon entering water, for artificial induced spawning. For the induced spawning hormone, mixed injection of LRH—A plus about 0.6 kg of PG gives good results. Use two injections: the first dose is 2-4 micrograms of LRH—A plus 0.1-0.2 PG per kilogram of broodstock body weight, and the second dose is 15-20 micrograms of LRH—A plus 0.5-1 PG, with the dose for males halved. The interval between the two injections is 8-12 hours. At a water temperature of 25-27 degrees C, the effect time is 8-10 hours. About 1 hour before the effect time, carefully observe the spawning behavior of the broodstock and carry out artificial insemination in time.