How to prevent frost in temporary culture of river crabs in winter
1. Ice breaking
The temporary culture density of commercial crabs is high, and the temperature is low after snow, so it is difficult to culture and manage. By hitting the ice hole or breaking the ice, on the one hand, we can observe whether the overwintering pond is short of water and lack of oxygen, on the other hand, it can make some harmful gases escape from the water body. When the water is anoxic (lower than 1.8mg/L), aquatic insects such as Cyclops and pine fleas can be seen near the ice eye, and measures to increase oxygen should be taken in time according to the observed conditions.
two。 85% of the oxygen in the oxygenated water comes from the photosynthesis and oxygenation of phytoplankton, and a small part comes from the dissolution of air and water replenishment.
1) the clear ice overwintering pool should be frozen with clear ice. If it is frozen into black ice, it should be re-frozen after it is broken to ensure that the clear ice area accounts for more than 50%. Snow is cleared in time after snow, and the snow-clearing area accounts for more than 80% of the pond area. Such as black ice or snow sweeping is not timely, resulting in insufficient light under the ice, blocking photosynthesis, easy to cause hypoxia.
2) Mechanical oxygenation can be done with 1.5-3.0 kW aerator running continuously for 2-3 hours. In the case of lack of oxygen and lack of water source in the overwintering pool, the water pump can be used to increase the oxygen of circulating water. You can also use a gas cylinder or an air pump to press the air into the water to increase oxygen.
3) in case of emergency, chemical drugs such as Zengyangling can be used to increase oxygen.
3. Replenish water
Ensure that the subglacial water depth of the overwintering pond is more than 0.8m. If it is lower than this number, it should be filled with water at any time. The temperature of replenished water should be more than 4 ℃.
4. Start the arrest
More than 0 ℃ can be caught in a dry pond, but less than 0 ℃ should not be caught, and water can be poured into the crab pond. Specific operation method: catch crabs in the dry pond during the day and return to the water in the evening.
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Experience of high-yield culture of river crab
The area of the river crab pond is 10-30 mu, the depth of the pond is 1.2-1.5 meters, the slope is 1: (2-3), and the ring ditch around the pond is 2 meters wide and 1.8-2.0 meters deep. The coverage area of aquatic plants should account for 40-60% of the pond area, and the suitable aquatic plants are Ellosia, bitter grass, verticillium verticillata and so on.
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Five key points of River Crab Culture in October
When we enter the later stage of river crab culture in October, we should strengthen the culture management to ensure that the river crab can promote fattening and growing darts. 1. Strengthen daily management and patrol the pond three times a day, one in the morning, one in the middle and one in the evening, mainly to observe the dynamics of river crabs in the pond. In the morning, we patrolled the pond to see if the crabs came ashore.
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