Practical methods for preventing cold of fish and soft-shelled turtle

1. Fish ponds choose leeward sunny deep water (more than 2 meters) fish ponds to winter naturally. Overwintering pool water should not be in a static state for a long time. Usually, part of the pool water should be replaced every 20 to 30 days, and 1/4 to 1/5 of the total pool water should be changed every time to prevent pool water pollution.

2. A windbreak wall and a cold shelter can be set up. A 2-meter-high windbreak barrier can be built with straw or soil on the north side of the fish pond, and a southward earth wall can be built on the east and west sides in the shape of a dustpan to reduce the attack of the north wind. When the cold wave strikes, the water temperature will not drop significantly. Drainage ditches should be built around fishing ponds to prevent stagnant water from flowing into the pond and lowering the temperature of the pond water. 1~2 cold-shelter holes with a depth of 2 meters and a diameter of 0.8 meters can be dug at 40 cm from the bottom of the north windproof wall. The wall of the windproof wall can be made of bricks or buried with ceramic pipes. Fish can enter the cold-shelter hole when cold wave strikes.

3. Building plastic film cold-proof greenhouses on the basis of setting wind-proof walls, plastic greenhouses are built on fishing ponds for heat preservation. A herringbone roof is erected along the edge of the pond with bamboo or wood. The distance from the ground to the roof is about 2.5 meters. Two layers of plastic film are covered on the roof, which is connected with the pool to form a sealing cover. The film can be sealed with mud around. Tilapia wintering pond generally covers an area of 40 ~100 square meters, and the water depth is more than 2 meters. Cement pond and earth pond can be used. The stocking density can be determined according to the water temperature, water quality and water quantity. Generally, 15 ~25 parent fish can be placed in each cubic meter of water, or 300 fish species below 10 cm. In ponds with better conditions, 30 ~40 parent fish and 400 ~500 fish species can be placed in each cubic meter of water. The high density stocking rate of flowing water culture can be referred to in flowing water pond, and it is appropriate to maintain dissolved oxygen in pond water at 2 mg/L. The mortality rate of juvenile soft-shelled turtle overwintering outdoors can reach 70%~80% without heat preservation measures. Therefore, if conditions are available, it is better to move the juvenile turtles into indoor ponds for overwintering, or to cover plastic greenhouses in outdoor ponds for overwintering. The stocking density is about 100 per square meter. If well managed, the survival rate of overwintering can reach 80%~90%.

When using plastic film greenhouses for wintering, thick straw curtains can be used to cover the temperature in the shed at night or in rainy days; and in sunny days, the straw curtains should be opened to use solar energy to warm up. When the air temperature and water temperature are too high, ventilation should be carried out and some new water should be added. In case of cold current invasion and water temperature decrease, the following heating measures can be taken: (1) steam heating method: add a furnace beside the wintering pool, boil the water with an iron pan, and make the steam enter the wintering pool from the special bamboo tube on the lid through the connected rubber tube to increase the temperature of the pool water. (2)infrared lamp heat method: in that wintering pool cover with sealed plastic film greenhouse, one infrared lamp of 250 W is installed every 35 square meters of water surface, 30 cm away from the wat surface, and a thick paper sheet or other water absorbing material which is easy to dry and absorb water is fixed at a distance of about 60 cm above the lamp, so as to prevent water condensed on the film from dropping on the lamp bulb and causing the lamp bulb to explode or catch fire. When the water temperature rises to 20℃, turn off the lights. The use of infrared heating benefits: infrared lamp heat, heating fast, less electricity, simple installation, but also sterilization, can prevent fish mildew.

4. Although the metabolism level of fish is low during overwintering, it still needs to consume a lot of energy, so feeding is still an indispensable work during overwintering. The main purpose of overwintering is not to gain weight, but to prevent frostbite, death and keep fish healthy. In order to prevent the physical decline of overwintering fish and enhance the resilience of fish themselves, efforts should be made in the selection of feed. Feed preparation should pay attention to the comprehensive and reasonable combination of nutrition, should not unilaterally pursue too high protein content and too fast growth rate, but should pay more attention to the balance of amino acids, vitamins and trace elements sufficient to ensure the healthy growth of fish. If tilapia overwintering period with feed protein content can be lower, about 20%, but the energy content should be higher, should be fine bran, bran, bean cake, malt and so on mainly feed, and often with feed some green duckweed, fresh leaves. In order to ensure the safety of soft-shelled turtle overwintering, it is necessary to enhance its stress resistance through intensive cultivation. Trionyx sinensis needs to supplement nutrition before and after overwintering. First, energy and protein should be strengthened, fat content can be increased by 3%~5%, and fresh feed should be fed as much as possible, and then vitamins, calcium and phosphorus should be supplemented accordingly. Insufficient sunlight in winter is prone to calcium deficiency, and more phosphorus is needed to increase yolk deposition. During the winter, the requirements of B vitamins, vitamin A, D, E and choline are higher than those in the normal feeding period. Therefore, these substances should be increased in an appropriate amount to improve the cold resistance of the turtle, enhance its disease resistance and prevent poor fat metabolism.

5. If the water temperature drops suddenly, heating measures should be taken immediately. The invasion of cold wave often causes continuous low temperature and overcast rain, which easily leads to the deterioration of water quality in fishing ponds, the incidence of pond fish, and some "old water" ponds are prone to anchor head disease. In addition to paying attention to changing water, frequently opening oxygenators, regularly applying microbial agents, etc. to improve water quality, pesticides should be applied in time for effective prevention and control to prevent the spread of pests and diseases.