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Winter fish need "three defenses"
The winter fishes are protected against shallow water, the second is against hypoxia, and the third is against cold. Preventing shallow water in winter has little rain, which can easily cause the water level of fish ponds to decrease. In addition, some fish farmers like to shallow the fish pond water, thinking that shallow water can make the fish reach the sun for heating purposes. In fact, the winter pond water is shallow, the water temperature changes quickly, and the temperature difference is large, which is unfavorable for fish growth. After the water level drops, the fish population density increases accordingly, and it is easy to cause lack of oxygen and stop the fish from growing or even die. Therefore, winter ponds should maintain normal water levels. Anti-hypoxia under normal circumstances, hypoxia pan-site mostly occurs in the summer and autumn high temperature season, rare in winter. However, in the Feishui Fish Pond, Shentan Deadwater Fishpond, and cage culture conditions, dead fishes with hypoxia can also occur in the winter. In the above waters, as the temperature drops, the temperature of the surface water drops, the density increases, and it sinks. The lack of oxygen in the bottom layer and the ooze-free floating of water will cause severe oxygen deficiency in the upper water. In addition, the photoperiod in the winter is short, the photosynthesis of the phytoplankton in the water is weakened, and the oxygen production is reduced, which also results in insufficient oxygen in the aquaculture water. Therefore, oxygenation measures should be taken in these waters in the winter to prevent flooding. Winter-chilled fish that are cold and cold are vulnerable to cold damage. Take the following measures to avoid cold and warming. (1) Avoid chills. On the north side of the pond, bamboo and bamboo are used to pile up and a woven bag or straw curtain is used as a barrier to reduce the cold currents. (2) warming by manure. About 500 kilograms of livestock and poultry manure is applied to the surface of the water per acre, and the water temperature is increased by utilizing the heat released from the fermentation of the fertilizer. (3) Smoke heating. During the winter day, the north wind whistled, and there was often frost at night. It was possible to use fire and straw to burn smoke on the shore to reduce frost. (4) Putting water plants. In winter, put the appropriate amount of water grass in the fishpond to allow the fish to avoid the cold in the grass. (5) Increase water injection. After the high temperature of the sunny afternoon, the water in the shallow water pond with higher water temperature is injected into the fish ponds to increase the temperature of the fish ponds.