Technical measures for releasing fish fry in winter

As the saying goes, "in spring, the fry has a plague, and in winter, the fry is three points longer." Practice has proved that the Winter Solstice to the Beginning of Spring is the best time to release fish species. There are three reasons: first, at this time, the fish species are strong, the scales are tight, and the adaptability is strong. Second, the water temperature is low, the activity of fish is weak, and the survival rate is high in the process of fishing and stocking. The third is to avoid the trouble of overwintering in the pond, so that the fish species can be evacuated and refined earlier, so as to promote the growth of early spring.

1. Transformation of fish ponds.

Use winter leisure to transform fish ponds, changing small ponds into large ponds, dead ponds into living ponds, and shallow ponds into deep ponds. The ponds with better conditions should also be renovated, drain the water, dig out too much silt after sun exposure or freezing, eradicate weeds, and strengthen the ridges.

2. Clear the pond and disinfect.

The commonly used disinfection drugs are quicklime, tea cake, bleach and so on. The disinfection effect of quicklime is the best, which can not only increase the calcium content of pool water, but also have the effect of direct fertilization. Disinfection should be carried out on a sunny day with dry disinfection, 50-80 kg of quicklime per mu, 5-10 cm of stagnant water in the pond, and 120-150 kg of quicklime if the water depth is 1 meter.

3. To improve the quality of water.

After 5 days of disinfection, the fish ponds were filled with water and 150-200 kg per mu of mature human and animal manure were applied to fertilize the water quality and cultivate biological baits in the water.

4. Fish species selection.

Fish species with the same age, consistent specifications, strong physique, intact scales, intact fins, thick back muscles, bright color, lively swimming and more than 12 cm in body length are selected for stocking.

5. Strict disinfection.

Fish fry should be disinfected into the pond. Generally, 3%-5% salt water can be used and fish fry can be washed for 20-30 minutes. Conditionally, 0.5 milliliters of diluted green and grass carp hemorrhagic inactivated vaccine can be injected into each of the green and grass carp species above 18 centimeters, and 0.3 milliliters per tail for those below 18 centimeters.

6. Variety matching.

The stocking variety and quantity are determined according to the water quality, water depth, bait and management level of the water area. A lot of forage, more grass, carp; fat ponds, silver carp; more bait at the bottom, more crucian carp and carp. The ratio of eating fish to silver carp is 30% "80%" and 70% "80%" in fat ponds, 25% "45%" and 75% "55%" in general waters, 60% "80%" and 40% "20% in running ponds or convenient injection and drainage, and adequate water supply. The ratio of middle to lower fish is 55% 65% and 45% 35%.

7. Aquaculture management.

In winter and spring, the temperature is low, in addition to the conventional requirements for the management of fish ponds, we should also pay attention to the "four precautions": first, to prevent the pool water from being too shallow, second, to prevent excessive feeding, third to prevent freezing and hypoxia, and fourth, to prevent water quality from being too fat.

(1) prevent frostbite. When the pond water temperature dropped to 1 ℃, the fish activity decreased, and below-3 ℃, grass, silver carp and bighead carp would freeze to death. Prevention and control methods: ① do a good job of cold protection and heat preservation to deepen the pool water; when the temperature of ② is high, properly feed some bean cake, rapeseed cake and so on to enhance the cold resistance of fish.

(2) Prevention and treatment of water mildew. The disease is prevalent in late winter and early spring. Sick fish swimming abnormally, loss of appetite, resulting in emaciation and death. Prevention and control methods: ① does not injure the fish in the process of fishing, transportation and stocking; ② sprinkles with 0.15g malachite green per cubic meter of water in the whole pool; ③ sprinkles with 2g gallnut per cubic meter of water; ④ soaks the fish with 50g / L salt water for 5 minutes.