Culture technology of black fish

Black fish has strong adaptability to the environment, low requirements for pond water quality, and can be farmed with high density. 8000 million fish can be released in each mu of pond, and the yield can reach 4000 million kilograms. Black fish can grow fast, and commercial fish can be developed in early spring. Blackfish has less disease, high survival rate, simple transportation of adult fish, and convenient for long-distance sales.

Artificial reproduction of black fish

1. Parent fish selection: the breeding season of black fish is in the middle of May every year. Mature and robust female and male black fish should be selected with the ratio of 1 ∶ 1 as parent fish. The method of distinguishing between male and female is that the abdomen of female black fish is dilated and soft, showing black and white, the outline of ovary is obvious, there are grooves in the center, and the reproductive foramen protrudes protruding, showing pink; the body color of male black fish is purplish red, there are small transparent white round spots arranged neatly from the bottom up on the dorsal fin, the abdomen is dark, the reproductive foramen is slightly enlarged, slightly concave, triangular, light pink. Before spawning, put the male and female fish in the cage for a day, do not feed, this is more conducive to spawning.

2.Parturition induction of parent fish: the female fish was injected twice, the first injection was the full dose of 1 stroke 3, the interval of 18 hours was 26 hours, and the remaining dose was injected once. The male fish dose was half of the female fish, and the female fish was injected with the second injection. Most of the fish are injected into the thoracic cavity, which is 45 °with the fish body, and the depth of the needle is about 1 centimeter. the commonly used hormones are common carp and crucian carp pituitary gland, with a dose of 480 / kg for females, which is halved by males, or chorionic gonadotropin, 16000-24000 IU / kg for females and halved for males.

3. Hatching of fish eggs

① artificial simulated natural environment hatching: after injection of oxytocin, males and females were put into the pool according to the ratio of 1 ∶ 1, so that they could spawn, fertilize and hatch naturally. After the fry are hatched, they are allowed to take care of them freely by making use of the protective habits of black fish. This method saves labor and time, but its disadvantage is that the survival rate of fish fry is low and the growth and development is inconsistent.

② artificial cage hatching: after injection to induce spawning, the male and female were placed in a cage of 4 to 6 meters in a ratio of 1 ∶ 1 to lay eggs and fertilized. After that, the parent fish were fished out and put into the pond. The fish eggs were placed in a 40-mesh cage with 10,000 fertilized eggs in each box and hatched by micro-running water. The hatching rate depends on the fertilization rate and water quality. 22-27 ℃, 32-48 hours, regular examination, timely removal of unfertilized eggs.

4. Seedling cultivation: before coming out of the film to 2cm, it should be raised in a cage of 1m × 0.5m × 0.5m made of 40 mesh cloth with a density of 2000 tails / m 2. After 4 days of emergence, rotifers, Cladocera, copepods, etc., were fed with a small number of times, once every 4 hours for 3 to 4 days. After that, the number of feeding increased, the times decreased, and gradually transitioned to 2 times a day. When the black fish fry reaches 2 cm, it is replaced by a cage made of summer flower net cloth with an area of 10 m 15 m 2, with a density of 500 m 600 pieces / m.

5. Feeding: zooplankton is the main food. At 4cm, add zooplankton to the fish paste. In order to prevent dirt and filamentous algae from blocking the mesh, scrub once a day, change the box once a week, and thoroughly disinfect the cage.

Feeding technique of black fish

1. Pond construction: choose the east-west direction, rectangular pond, the bottom of the pond is soil, the depth of the pond is 2-2.5 meters, the water depth is 1.5-2 meters, the inlet and drainage should be equipped with anti-escape facilities, and 100kg / mu of quicklime should be thoroughly disinfected 15 days before breeding.

2. Fish stocking: before entering the pond, the fish should be soaked in 3% to 5% salt water for 10 minutes for 15 minutes, and then put into the pond. The fish species with a body length of 10 centimeters and 14 centimeters will have a stocking density of 9000 million fish per mu and 16 fish species per mu, and the stocking density is 8000 fish per mu.

3. Daily management: pay attention to observe the feeding, activities, morbidity trend and environmental changes of black fish. Change the pool water 4 times a week in spring, a small change every 3 days in the high temperature season, a big change every 7 days, enter and drain to catch the escape net, and the pool ridge is more than 50 cm above the surface of the water. For the discharged sewage, the necessary sewage treatment should be carried out.

4. Feed feeding: feed for black fish, including artificial compound feed, small miscellaneous fish of fresh water or sea water, and scraps of livestock and poultry after slaughter. Before feeding, small miscellaneous fish need to be sorted to remove fish with hard spines, such as Pelteobagrus fulvidraco. Before feeding, use slapping as a signal to concentrate distant fish near the bait table to reduce feed waste. The initial feeding amount is 10% of body weight, and then it can be appropriately reduced to about 5% of body weight. It should be fed with one spoonful, so that the waste of feed is less. Feeding should adhere to the "four-fixed" principle, and each pond should choose 3-4 feeding points. The way of intensive culture is adopted, with a body length of more than 10 cm. After 8-9 months of culture, the survival rate is 75%-80%, the average body weight is 0.5-0.7 kg, and the yield per mu is 4000-5000 kg. Plant some aquatic plants in the pond, such as Rabdosia angustifolia, Sophora flavescens, water peanut, etc., and the planting area should be controlled at 1 / 3 of the pond area.

Prevention and treatment of common diseases

At present, in the process of black fish culture, the common diseases are hemorrhagic disease, white skin disease, water mildew disease, melon disease, rotifer disease and so on.

1. Hemorrhagic disease

[pathogen] many kinds of bacteria and viruses.

[symptoms] there were bleeding stripes along the lateral lines of the vertical fish body at the base of the pectoral fin and on both sides of the body wall near the posterior edge of the operculum, and a large number of deaths occurred in 3-4 days, and it was easy to break out from June to September.

[prevention and control] the pond should be cleared thoroughly after winter fishing, and the bait fish should be disinfected with salt water before feeding; sprinkle with formalin in the whole pool to make the water concentration reach 20,30ml / m 3, or sprinkle with chlorine dioxide solution in the whole pond to make the pond water concentration reach 0.5g / m 3, repeat once after 6 days. Oral Yufukang No. 2 or Yuxue Powder or Yuxuekangtai can be taken orally, and the dosage is used according to the instructions.

2. Red skin disease

[pathogen] Trichoderma fluorescens.

[symptoms] Local bleeding on the body surface and shedding of fish scales, especially on both sides of the abdomen, have the phenomenon of fin decay, the fish move slowly, and sick fish often float on the surface of the water and are weak. Often secondary to water mildew, until death.

[prevention and treatment] thoroughly clear the pond with quicklime to avoid damage to the fish; disinfect the fish with 0.5 mg / L of Xiaoling or other chlorine-containing disinfectants, such as trichloroisocyanuric acid, sodium dichloroisocyanurate, chlorine dioxide, etc.; take orally Yushikang and Yuxuekang, 250 grams per 100 kg of fish or according to the instructions, mix into the feed and feed for 3 days.

3. Water mildew

[pathogen] water mold.

[symptoms] occur in all stages of the growth of black fish, and it is not easy to observe in the early stage after infection, when the water temperature rises to about 18 ℃, a large number of outbreaks occur; blood spots appear on the fish's body surface, loss of appetite, weight loss, melanin regression in the focus, grayish white, dim color, and wandering alone. Finally, the flocculent white filaments grow, and the muscles are turbid white until death.

[prevention and treatment] before stocking, the pond was dry cleaned with 100,150kg / mu of quicklime, and the adult pond was regularly disinfected with quicklime or bleaching powder. During the onset of the disease, the whole pool of potassium permanganate of 30kg / m ~ 3 could also be sprinkled. The process of seedling fishing, transportation and operation should be careful to prevent fish from injury, and soak in 3%-5% salt solution for 10-20 minutes.

4. Rotifer disease

[pathogen] rotifer.

[symptoms] it mainly harms the fry and fingerling stage of black fish. It can occur all the year round, but it is more popular from April to July, and the suitable temperature is 20: 28 ℃. The pond is small, the water is shallow, the water quality is bad, the bait is insufficient, the stocking is too dense, the continuous rain and so on are easy to occur; the diseased fish have a lot of mucus, most of the fish body or the whole body is white, swimming slowly, the fish body is thin, and it is difficult to breathe and die.

[prevention] the mixture of copper sulfate and ferrous sulfate (5 ∶ 2) was sprinkled in the whole pool to make the water content up to 0.7mg / L. It can effectively kill rotifers on the fry, body surface and gills of black fish.