Which four levels should be adopted in fish culture at the beginning of spring?

1. Fertilizer application: when the water temperature of the pond is stable at 8 ℃ ~ 10 ℃ in early spring, fertilizer is applied to cultivate natural bait in the water. The amount of fertilization should be determined according to the fat and thin water quality and the quality of fertilizer, 60 kilograms per mu of human feces and urine, or 100 kilograms of animal manure. If chemical fertilizer is used, the ratio of nitrogen, phosphorus and potassium is 1 ∶ 1 ∶ 0.5. when topdressing, it is crushed first and then sprinkled in the whole pond, with a total dosage of 3 kg / mu and an interval of 5 / 10 days. It is appropriate to keep the water quality of the pond yellowish brown or yellowish green with a transparency of about 30 cm.

Second, bait off: when the water temperature reaches 10 ℃, fish begin to feed and grow. Early spring bait should be based on bean cake, wheat bran, cornmeal and other concentrate feed, fixed point every day, regular feeding, each feeding should be 1.5%-3% of the fish body weight. After that, the amount of bait gradually increased with the increase of water temperature, and it was fed twice a day. At the same time, the pond where grass carp was mainly raised should be fed with an appropriate amount of land and water grass, and the best feeding amount should be 4-6 hours after feeding. The specific amount of bait should also be flexibly controlled according to the water temperature, weather and the feeding situation of fish.

Third, water injection pass: in early spring, due to low water temperature, small fish, less active food intake, the pool water should not be too deep. With the increase of water temperature, the fish body increases and gradually deepens the water level. In early spring, it is best to change the water once, and replace it with 1 per cent of the water in the whole pool. After that, the water level will be injected every 15 days, raising the water level by 10 cm to 15 cm each time, keeping the pond water level about 1 m from March to April, and preventing the inflow of sewage and enemy organisms.

Fourth, disease prevention: the pond should be managed by special personnel, patrol the pond every morning and evening, check the quality of water, and determine the amount of fertilization and bait. Salvage the residual bait in time, keep the pool water clean, and forbid feeding spoiled feed. Regular medicine to prevent fish disease, every 15 days with 1PPm bleach and 0.7PPm copper sulfate solution sprinkled alternately in the whole pool, if found that fish disease should be diagnosed and treated in time.