What practical cold-proof measures are there for fish and soft-shelled turtle farming

1. Pond selection Choose a deep-water (over 2 m) pond sheltered from the wind and facing the sun for natural overwintering. The water in the overwintering pond should not remain stagnant for long periods; usually replace part of the pond water every 20 to 30 days, each time replacing 1/4 to 1/5 of the total pond water, to prevent pond water contamination.

2. Set up windbreak walls and cold-shelter holes On the north side of the pond, a 2 m high windbreak barrier can be built with straw or earth, and on the east and west sides build earthen walls sloping toward the south, forming a winnowing-basket shape, to reduce attacks by the north wind, so that when a cold wave strikes the water temperature will not drop noticeably. Drainage ditches should be built around the pond to prevent accumulated water outside the pond from flowing in and lowering the pond water temperature. In the north windbreak wall, at 40 cm from the pond bottom, 1 to 2 cold-shelter holes 2 m deep and 0.8 m in diameter can be dug; the hole walls can be built with bricks or fitted with ceramic pipes, and when a cold wave strikes the fish can enter the cold-shelter holes.

3. Build plastic-film cold-proof greenhouses On the basis of setting up windbreak walls, build plastic greenhouses over the pond for insulation. Use bamboo or wood along the pond edge to build a ""-shaped (inverted V-shaped) roof frame, with a distance of about 2.5 m from the ground to the roof top, covered with two layers of plastic film, connected with the pond edge to form a sealed cover, and the film can be sealed around with mud. Tilapia overwintering ponds generally have an area of 40 sq m to 100 sq m, with a water depth of over 2 m; both cement ponds and earthen ponds are acceptable, and the stocking density can be determined by water temperature, water quality and water volume; generally 15 to 25 brood fish can be stocked per cubic meter of water, or 300 fingerlings under 10 cm. For ponds with better conditions, 30 to 40 brood fish can be stocked per cubic meter of water, or 400 to 500 fingerlings. For flow-through ponds, the high-density stocking rate of flow-through aquaculture can be used as a reference, and it is appropriate to maintain the dissolved oxygen in the pond water at 2 mg/L. For juvenile soft-shelled turtles overwintering outdoors, without insulation measures the mortality rate can reach 70% to 80%. Therefore, if conditions permit, juvenile soft-shelled turtles are best moved into indoor ponds for overwintering, or covered with plastic greenhouses in open-air ponds for overwintering, with a stocking density of about 100 per sq m; with good management, the overwintering survival rate can reach 80% to 90%.

When using plastic-film greenhouses for overwintering, at night or on cloudy and rainy days thick straw curtains and the like can be used as cover to maintain the temperature inside the greenhouse; on sunny days the straw curtains and other coverings should be lifted to use solar energy for heating. When the air temperature and water temperature are too high, ventilate and exchange air, and add part of fresh water. When a cold current strikes and the water temperature drops, the following heating measures can be taken: (1) Steam heating method: set up a stove beside the overwintering pond, boil water in an iron pot, and let steam pass from a specially made bamboo tube on the pot lid through a connected rubber hose into the overwintering pond to raise the pond water temperature. (2) Infrared lamp heating method: in the above overwintering pond covered with a sealed plastic-film greenhouse, install 1 250-watt infrared bulb for every 35 sq m of water surface, 30 cm above the water surface, and at a distance of about 60 cm above the bulb fix a piece of thick cardboard or other water-absorbing material that dries easily, to prevent water droplets condensed on the film from water vapor falling on the bulb and causing the bulb to burst or start a fire. When the water temperature rises to 20°C, turn off the lamps. Benefits of using infrared heating: infrared lamps give off a large amount of heat, heat up quickly, use little electricity, are simple to install, and also have a sterilizing effect, which can prevent fish from developing mold diseases.

4. Feed concentrated feed on a fixed schedule, in fixed amounts and of fixed quality Although fish have a relatively low metabolic level during the overwintering period, they still need to consume a large amount of energy, so during the overwintering process feeding is still an indispensable task. The main purpose of overwintering is not to make the fish gain weight, but to prevent the fish from being frostbitten or dying and to keep the fish constitution healthy. To prevent the constitution of overwintering fish from declining and to enhance the fish's own stress resistance, effort should be put into the selection and formulation of feed. When formulating feed, attention should be paid to comprehensive and reasonable nutritional matching; one should not one-sidedly pursue excessively high protein content and excessively fast growth speed, but should pay more attention to the balance of amino acids and the sufficiency of vitamins and trace elements, to ensure the healthy growth of fish. For example, the protein content of feed used during the overwintering period for tilapia can be lower, at about 20%, but the energy contained should be relatively high; feeding should mainly be based on fine rice bran, wheat bran, soybean cake, malt and the like, and often supplemented with some azolla and fresh tender vegetable leaves. To ensure that soft-shelled turtles overwinter safely, in particular their own stress resistance should be improved through intensive cultivation. Soft-shelled turtles need supplemental nutrition before and after overwintering; first, energy and protein supplementation should be strengthened, the fat content can be increased by another 3% to 5%, and as much live feed as possible should be fed, and then targeted supplementation of vitamins and calcium, phosphorus, etc. should also be carried out. Insufficient sunlight in winter easily causes calcium deficiency, and more phosphorus is needed to increase yolk deposition. During the overwintering period, soft-shelled turtles' requirements for B vitamins, vitamins A, D, E and choline, etc. are greater than during the normal rearing period, so these substances should be appropriately increased, which helps improve the soft-shelled turtle's cold resistance, enhance its disease resistance, and prevent poor fat metabolism.

5. If the water temperature drops suddenly, heating measures should be taken immediately A cold wave strike often causes continuous low-temperature overcast and rainy weather, which very easily leads to deterioration of pond water quality and disease in pond fish; for example, in some "old water" ponds, silver carp and bighead carp are prone to anchor worm disease, etc. In addition to paying attention to changing water, frequently turning on aerators, and periodically applying microbial preparations to improve water quality, insecticides and other chemicals should also be applied in a timely manner for effective control, to prevent the spread and expansion of diseases and insect pests.