Experience of overwintering conservation in outdoor ponds of cultured tilapia

At present, most of the overwintering methods of tilapia are indoor ponds, which require high conditions, and the number of overwintering fish is limited. In order to further increase the number of overwintering fish species, the techniques of overwintering conservation in outdoor ponds are introduced.

1. Overwintering equipment outdoor pond, area 1-1.5 mu, depth 1.7-1.8 meters, water depth 1.5-1.6 meters, the best stone wall and bottom, sediment not more than 10 cm, the less the better, one end of the pond with 1-2 water level balance pipes (1.5 meters from the bottom), 1-2 sewage pipes (0.5 meters from the bottom), all connected to the drainage ditch, one hot water pipe and one cold water pipe (both are close to each other). If the hot and cold water is mixed and then injected into the overwintering pool, there are two 1.5 kilowatt impeller aerators (one impeller type and one water wheel type).  2. The chemical index of water quality shall conform to the water quality standard of freshwater fishery. In addition, dissolved oxygen and water temperature should depend on the specifications of fish species entering the pond and the requirements of leaving the pond. That is, if fish species are required to have a greater growth during the overwintering period, the dissolved oxygen and water temperature should be appropriately higher; on the contrary, if only for species conservation, the dissolved oxygen and water temperature can be appropriately lower.  3. The fish species enter the pond before and after the National Day, and the pond is thoroughly cleared with quicklime before entering the pond. The fish density in the pond depends on the specifications of the fish species in the pond and the requirements for leaving the pond, that is, if the fish species are required to increase significantly after overwintering, the fish density should be smaller; on the contrary, only for the purpose of species conservation, the fish density can be larger, in the range of 5-10 kg / m2.  4. The feed requires high density of overwintering fish and insufficient natural bait, so high-quality artificial pellet feed should be fed according to the specifications of pond fish during overwintering, and the particle size should be adapted to the caliber of fish to ensure the palatability of the feed.  5. There are three keys to water quality regulation in high density overwintering conservation: dissolved oxygen, water temperature and dirt, dissolved oxygen is regulated by aerator, and water temperature and dirt are adjusted by changing water.  dissolved oxygen: if the size of the fish species is small and the weight is small, then, after the fish species enter the pond, an impeller aerator should be placed in the pond, and the start-up time should be controlled at 30 minutes / hour. with the raw fish, the start-up time should be increased to 50 minutes / hour. according to the growth of the fish in the pond, another aerator should be added at the right time, and the start-up time is 40 minutes at the same time, then stop one and the other continues to work. After 20 minutes, the two machines are turned on at the same time, and then stop the other for 20 minutes after 40 minutes, so turn on again and again. After April, the two machines should basically keep working day and night.  water temperature: warm water is added by the inlet pipe, and the pool water is mixed evenly through the role of the aerator, because the sewage pipe is generally not opened, so that with the increase of warm water, the excess pool water flows out of the water level balance pipe. Due to the addition of warm water and the outflow of the original pool water, the pool water can be controlled at a certain temperature.  dirt: a large number of fish, a large number of metabolites, coupled with the influence of residual bait, the pool water deteriorates rapidly, although the water level balance pipe can discharge part of the dirt, but the quantity is limited, a large number of dirt still needs to be discharged by the sewage pipe. When discharging sewage, open the sewage pipe valve to lower the water level of the pool to 0.5 m, then close the valve and add water to restore the water level to 1.5 m; another method is to open the valve to lower the water level to 0.5 m, add water to the pool, flush the precipitation in the pool, flow out the water from the discharge pipe, and then close the valve to restore the water level to 1.5 m. As a result of frequent discharge, so that the pool sewage will not accumulate too much.  6. Feeding and management fish fingerling are fed with formula feed six times a day after entering the pond, at the time of 7:00-8rig 00lv 900-10lv 00lv 1100-12lv 00L 1300-14:00, 5:00-16lv 00lv 1700-18lv 00. The  feeding method is that after the fish is put into the pond, the sound is made by hitting the fish before each feeding, and then fed, which can form the feeding conditioned reflex of the fish in the pond for one week. The amount of feeding depends on the eating situation of pond fish, eat more, eat less, ensure that the pond fish is 70% or 80% full, which not only meets the physiological needs of fish, but also improves the feed utilization rate.  7. Disease prevention and treatment uses the combination of internal and external medicine to prevent and cure fish disease. Prevention: internal administration: medicine is made into bait for regular feeding, there are two kinds of drugs: Chinese herbal medicine and antibiotics, the dosage of Chinese herbal medicine is 5 grams per 10 kg fish, once a month, once for three days; the dosage of antibiotics is 4 grams per 100 kg fish, once a month, once three days, the two drugs are cross-used for half a month. External use: the way of use is to sprinkle the whole pool, the types are: quicklime, mixture of copper sulfate and ferrous sulfate (5 ∶ 2), bleach, Weidao brand disinfectant, the dosage is 30ppm, 0.5ppm, 1ppm and 0.5ppm, respectively, one is used every 10 days, and used in rotation (only one of them is used in each rotation because the effect of bleach is similar to that of Weidao brand disinfectant). Treatment: during the overwintering period, the fish disease that occurs is mainly rotifer, followed by tongue cup disease. The treatment measure is to sprinkle the mixture of dissolved copper sulfate and ferrous sulfate (5 ∶ 2) into the pond in the morning, and change the water greatly that night, the method is to open the sewage pipe, make the water drop to 0.5m, and then add fresh warm water to restore the pond water, thus playing a better treatment effect on the fish disease. As for the concentration of the mixture, because it is often used in disease prevention, causing pathogens to have a certain resistance to drugs, so in the treatment of diseases, the concentration should be appropriately higher than the general concentration according to the actual situation. 8. The overwintering effect is managed by overwintering, the overwintering fish can produce about 15 kg of overwintering fish per square meter of water, the specification is about 50 grams per tail, the survival rate is more than 95%, and the net income per square water is more than 100 yuan.