Preparations for Winter Fish Farming and Their Impact on Fish Culture

As winter arrives, temperatures drop lower and lower, and in some places the water surface begins to freeze, which has a certain impact on fish culture. So what preparations should be made for winter fish farming? What impact does it have on fish culture?

1. What impact does winter have on fish culture?

1. In winter, the daylight period is relatively short, light intensity is relatively weak, and water temperature is low, which greatly affects the growth and reproduction of some algae. The water quality of fish ponds in winter becomes more turbid and lean, the balance of algae and bacteria is easily disrupted, and bacterial diseases (such as hemorrhage disease in bottom-dwelling fish) are more likely to occur;

2. As cold air intrudes frequently, wind direction shifts and rapid cooling of the surface water cause strong convection in the water body, which easily leads to water instability. The concentrations of toxic and harmful substances such as ammonia nitrogen, nitrite and hydrogen sulfide easily exceed standards, and the water temperature drops rapidly and by a large margin, causing great stress to fish;

3. Winter is the late stage of farming. The accumulation of residual bait and feces at the bottom of the pond, and the consumption of carbon sources, phosphate fertilizer and other substances in the pond without timely replenishment, affect the normal operation of the material cycle in the pond, reduce the overall productivity of the pond, and further accumulate harmful substances such as ammonia nitrogen and nitrite;

4. Other aspects: unsatisfactory fish prices lead to too many fish being held over, causing oxygen deficiency and fish gasping at the surface; feeding too much or too little may cause waste or weight loss.

2. What should be paid attention to in winter fish farming?

1. Build a simple windbreak wall

Prevent cold damage by setting up cold-proof windbreak walls and cold-avoidance holes. The method is as follows: on the north side of the fish pond, build a windbreak barrier one to two meters or more high with straw or earth, and build south-slanting earthen walls on the east and west sides in a dustpan shape to reduce attacks from the north wind. Drainage ditches should be built around the pond to prevent accumulated water outside the pond from flowing into the pond and lowering the pond water temperature. On the north windbreak wall, 40 cm from the pond bottom, 1 to 2 cold-avoidance holes 2 m deep and 0.8 m in diameter can be dug. The hole walls can be built with bricks or buried ceramic pipes. When a cold wave strikes, fish can hide in the cold-avoidance holes to escape the cold. Practice has proven that this cold-proof method is low in cost and obvious in effect.

2. Increase pond water depth

Generally speaking, a pond that is sheltered from the wind and faces the sun with a water depth of more than 2 m can allow fish to overwinter safely. As long as extremely cold weather is not encountered, getting through a normal winter is no problem. At the same time, the water in overwintering ponds cannot remain static for a long time. Water can be changed appropriately according to local temperature conditions, changing 1/4 to 1/5 of the total pond water each time to prevent pond water pollution.

3. Feed appropriately to maintain the physique of overwintering fish

In the past, many fish farmers stopped feeding as soon as winter came and did not start feeding again until spring. In fact, if fish are fed appropriately during overwintering, the fish will not lose weight and their cold resistance can also be increased, especially when feeding high-protein feed. Increasing feed with high protein content can improve cold resistance and prevent the physique of overwintering fish from declining. When preparing it, attention should be paid to nutritional balance, especially the balance of amino acids and sufficient vitamins and trace elements. Fish feeding should also follow the “three fixeds&rdquo, namely fixed quality, fixed time and fixed quantity. The rhythm of winter feeding must be well controlled. If too little is fed, the physique of the overwintering fish may weaken, the intestinal tract and stomach wall may become thinner, and the fish may lose weight and grow more slowly; if too much is fed, the fish cannot finish it, which not only causes waste, but the residual bait also deteriorates the pond water quality.

4. Oxygenation, insect killing and disinfection cannot stop

Ponds can also become oxygen-deficient in winter. If the aerator is properly turned on in winter, the pond water can become more lively and the dissolved oxygen situation in the water can be improved. In addition, a water surface that remains static for a long time is prone to freezing in winter, and once it freezes, the trouble becomes even greater. In winter, pond water quality is prone to aging. Fish farmers should regularly apply microbial preparations and other substances to improve water quality. Low water temperature leads to poor algal vitality and easy aging, slow metabolic renewal, and relatively few planktonic animals and plants. Especially in ponds with old water, silver carp and bighead carp are also prone to diseases such as Lernaea parasitosis under oxygen-deficient conditions. Therefore, while oxygenating, insecticidal agents should also be applied in a timely manner for effective prevention and control, so as to achieve simultaneous prevention and treatment of cold damage and disease. Before a large temperature drop, when there are 2-3 consecutive sunny days, broad-spectrum insecticides can be chosen for insect killing; after insect killing, it is recommended to use disinfectants for disinfection to promote the timely repair of wounds caused by parasites on fish and avoid infection.

5. Build plastic greenhouses

Even better than windbreak walls and cold-avoidance holes is building plastic greenhouses. The method is to build a “”-shaped roof over the pond along the pond edge with bamboo or wood. The distance from the ground to the roof top is about 2.5 m. Two layers of plastic film are covered on top, connected with the pond edge to form a sealed cover. The film can be sealed around with earth. At night or on cloudy and rainy days, thick straw curtains and other coverings can be used to maintain the temperature inside the shed. On sunny days, the straw curtains and other coverings can be properly lifted to use solar energy to raise the water temperature. When the water temperature is too high, ventilate and exchange air, and add some new water. If species with high economic value and poor cold tolerance are being farmed, heating facilities should also be adopted if necessary.