Why pond fish lack oxygen in winter

This is because when the temperature drops, the surface water temperature of deep-water ponds, fertile water ponds and cage high-density aquaculture waters is lower than that of the lower layer, and the specific gravity of water is higher than that of the lower layer. As a result, the surface cold water sinks and the lower warm water floats, forming vertical convection of the water body. On the other hand, the water body of the deep water layer is anoxic or even anaerobic, and the anoxic and anoxic water body floats up, resulting in serious hypoxia in the upper water body. On the other hand, the vertical movement of the water body accelerates the oxidation and decomposition of residual bait and feces deposited at the bottom of the pond, and increases the oxygen consumption in the water body. On the other hand, due to the lack of sunlight in winter, weak photosynthesis of phytoplankton in water and less oxygen production, resulting in insufficient dissolved oxygen in the culture environment, coupled with high culture density, it is easy to cause anoxic floating head or even death of fish.

In order to prevent anoxia of pond fish in winter, three measures can be taken: first, to control the culture density of fish, especially in the waters of cage culture, the area of the cage should be controlled within 3% of the total water surface to ensure sufficient dissolved oxygen and avoid the deterioration of the water body. Second, to achieve scientific fertilization, fertilization should be appropriate, methods should be appropriate, to prevent the water quality from being overfertilized and polluted. Third, it is necessary to catch in time in order to reduce the culture density and reduce the water load.