At present, the overwintering technology for fish used in the north is mainly under-ice bioaerobic overwintering technology. This technology is mainly to promote the photosynthesis of phytoplankton in the water under the ice and release more oxygen by adopting various technical measures. The survival of fish requires increasing the density and survival rate of fish overwintering. 1. Choose the best winter water for wintering. It is best to use new water, such as rivers, lakes, reservoirs, water, springs, wells, etc., and add a small part of the old water (feeding used water), new and old water ratios. For 3-4:1. The old water is rich in phytoplankton, which is beneficial to light and oxygenation. If the overwintering water is dominated by old water, disinfection is required. The lime water is poured into the whole pond and splashed with 20-25 kg of lime per acre. 2. Kill large-scale zooplankton in the water. Large-scale zooplankton feed on phytoplankton. It also consumes oxygen during wintering. Therefore, measures should be taken to kill it. Ten to fifteen days before freezing, crystals of trichlorfon are splashed in Quanchipia and 0.5 grams of crystal trichlorfon is used per cubic meter of water. Other insecticides can also be used. 3. Keep clear ice and ice can maintain high light transmittance. Keeping clear ice should take the following two measures: The first is to prevent snow blocking bubbles. The snow bubble is a layer of iced ice formed on the surface of the water when the pool water just touches snowfall. If snow capping occurs, clear windless weather should be selected, and the iced ice should be crushed and removed, so that a clear layer of ice can be formed on the surface of the water. The second is frequent snow and dust. The larger the area of ​​the snow sweeping on the ice, the better. The small pool is best to sweep clean. The larger wintering pool can sweep a 1-meter-wide transparent road every 0.5 meters, preferably from north to south, for better lighting. In addition, the dust on the ice must be cleaned in time. 4. Pay attention to supplement the nutrients to the water body under the ice. If the dissolved oxygen in the water is found to be drastically reduced, it is the lack of fertilizer in the water body and the chemical fertilizer can be chased. Apply 1.5-2 kg of urea and 1.5-2 kg of superphosphate per acre of water. The method of hanging bag is used to fertilize and make ice eyes. The fertilizer is hung in the water under the ice, and 4-6 bags are hung per acre of water.
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