Cultivation techniques of black fish fry

Black fish is a common name for snakehead, also known as black mullet, raw fish, wealth fish, snake fish, fire fish, etc., ferocious, strong fecundity, great appetite, and can often eat all other fish in a lake or pond. In China, it is a common edible fish with large size, fast growth and economic value. Let's take a look at the cultivation techniques of black fish fry.

Breeding habits of black fish

1. Spawning time: the spawning season of black fish varies with different climatic conditions. In South China, the spawning season is from mid-April to mid-September, with the peak in May and June, and that in the middle area is from May to July. The breeding water temperature is 18 ℃-30 ℃ and the optimum water temperature is 20 ℃-25 ℃.

2. Sexual maturity: the sexual maturity age of black fish is also slightly different in different regions. In South China, the gonads of winter fish with a body length of more than 20 cm have matured, while those in the Yangtze River basin need 2 winter seasons and a body length of about 30 cm to spawn. They can reproduce naturally in ponds, ditches and reservoirs, and spawning grounds are generally distributed in shallow water areas with lush water plants.

3. The number of eggs: the number of eggs laid and the number of eggs laid by black fish are related to the size of their parents. The number of eggs laid by snakehead snakehead with a weight of 0.5kg is usually about 20-30 000 eggs per kilogram of body weight.

Artificial propagation of black fish

1. Breeding equipment: the breeding facilities of the black fish are the equipment used for the reproduction of the four major domestic fish. The spawning pool is round, with a diameter of 8 meters and a depth of 1.5 meters. The hatching equipment is a throwing incubator, each tank contains about 500 kilograms of water, and the filter tank cover is 60 meshes. The fish nest is brown slices and clam shells.

2. Parent fish selection and cultivation: parent fish try to choose natural catches from nearby ditches and lakes, with specifications of more than 80g / tail, normal shape, disease-free and injury-free, cultivated in the pond. When the water temperature is above 15 ℃, feed a small amount of small fish and shrimp, snail meat, bean cake, etc., and often patrol the pond for observation, adding new water appropriately.

3. Male and female identification: the female fish is significantly smaller than the male fish, the female fish has a graphical urinary pore and almond-shaped reproductive foramen, the abdomen is dilated and soft at maturity, the reproductive foramen is slightly red and everted, the male fish has only one cloacal foramen, and the male-male ratio of the parent fish is 1RU 1.2.

4. The method of inducing spawning: the natural spawning in the pond did not inject drugs to induce spawning. When the water temperature reached 18 ℃ in early April, it was found that when the snakehead was swimming in the upper layer of the pond, brown slices and a number of large clam shells were arranged on the edge of the pond, and water was injected to make the pond water show micro-flow to stimulate parent fish estrus and let them lay eggs naturally in brown slices and clam shells. The parent fish spawned in the spawning pool were injected with gonadotropin 2 (LRH-A) and chorionic gonadotropin (HCG), and the injection site was at the base of Tushuo. On April 6 each year, LRH-A was injected for the first time at a water temperature of 19 ℃, and the mixture of LRH-An and HCG was injected for the second time at an interval of 12 hours. After injection, the parent fish were injected into the spawning pool, and the oestrus was stimulated with micro-running water, and brown slices and large mussel shells were arranged. Let it lay eggs naturally.

5. Artificial hatching: the fertilized egg is yellowish and round, and the egg membrane is transparent and sticky. After the parent fish in the pond and spawning pond have finished spawning, take out the brown flakes and clam shells with fertilized eggs in time, gently wash away the mud and dirt, transfer them to the incubator, and hang the brown flakes and clam shells in the water.

Cultivation and management of black fish fry

1. Fish fry restocking: 1-year-old fish fry are reared in static water cement ponds with 200-300 summer flowers per square meter and 300-500 fry per square meter in micro-flow cement ponds, reaching 0.05-0.10 kg / tail at the end of the year. Before releasing the seedlings, the fish should be bathed in 2% Mak 3% salt water for 3-5 minutes to kill germs and enemies.

2. Feed: the bait is mainly mackerel, surimi and small fish, shrimp and so on. The daily feeding amount is 5% of the total body weight of the fish, and it is fed 2-3 times a day. When feeding, the beating sound is used as a signal to make the seedlings form a conditioned reflex and float in clusters to grab food.

3, water quality regulation: when using the above-ground static water cement pool for cultivation, the sewage should be discharged every 1-2 days, and the water should be changed at the same time, and the amount of water should be changed for 1-3. When using the above-ground micro-running water cement pool for cultivation, although there is no special change of water, it is necessary to discharge the sewage at the bottom every 7-10 days. When the semi-underground cement pool is not easy to discharge, siphon method can be used to clean up every 5-7 days. At the same time, add new water.

4. Net separation: every time the seedlings grow a specification, that is, every 3.5 cm long, the seedlings should be screened and raised in time to make the seedling specifications in each pool as neat as possible.

5. Patrol the pond to prevent disease: patrol the pond twice a day in the morning and evening. When patrolling the pond, pay attention to observe the feeding, activities and changes of water quality of fish fry, and solve problems in time. In order to prevent the occurrence of fish disease, quicklime or bleach solution should be sprinkled regularly.