Technical measures for River Crab Culture to deal with the influence of Ice and Snow disaster

First, commercial crab management: 1, hit the ice eye and break the ice. The temporary culture density of commercial crabs is high, and the temperature is low after snow, so it is difficult to culture and manage. Through ice hole or ice breaking, 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 there is no oxygen in the water (lower than 1.8mg/L), the gathering of aquatic insects such as Cyclops and pine fleas can be seen near the ice eye, and timely measures should be taken according to the observed situation. 2. Increase oxygen. 85% of the oxygen in the water comes from the photosynthesis of phytoplankton to increase oxygen, and a small part comes from the dissolution of air and water replenishment. (1) the overwintering pool should be frozen with clear ice. If it freezes 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. The 1.5-3.0 kilowatt aerator can be turned on continuously for 2-3 hours to increase oxygen. In the case of lack of oxygen and lack of water source in the overwintering pond, 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) Chemical oxygenation. 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 pool is more than 0.8 meters. If it is lower than this number, it should be filled with water at any time. 4. Start the arrest. Take the temperature as the key to arrest. Catch crabs in dry ponds above 0 ℃ and water in crab ponds below 0 ℃. Specifically, crabs are caught in dry ponds in the daytime and back in crab ponds in the evening. Second, river crab species management: after snow, due to the poor physique of river crabs, water hypoxia, freezing and enemy damage, if poor management, often lead to the death of young crabs. In order to make the river crab survive the winter safely, crab farmers can take the following methods: 1, water level. The overwintering pond should be kept at a depth of about 1.5 meters, and river crabs will not be frostbitten and frostbitten to death only in deeper water. Always check the overwintering pond for leakage. The crab pond must not be kept at a low water level for a long time, otherwise, although the crab is hidden in the cave or soil, it is still exposed to the air and will be frostbitten or frostbitten to death. When it is found that the water level is falling, it is necessary to add water in time, and the temperature difference of influent water is less than 2 ℃. 2. Bait feeding. The river crab basically stopped eating after the snow disaster. When the ice and snow melts, the activity of river crabs increases, so pay attention to keep the fresh water quality. When the water temperature rises to about 10 ℃, appropriate increase in fat, protein high animal feed, cooked wheat, corn and so on. 3. Daily management. There should be a special person to manage the patrol of the pond, and the frozen pond noodles should be broken and frozen in time, so as to minimize the phenomenon of disturbing crabs such as sailing and fishing for fish and shrimp, so as to prevent crabs from being frightened and running around and causing injuries and physical exertion. Third, the management of parent crab ponds: the starting and transportation of parent crabs and the decrease of temperature will produce strong sexual stimulation to parent crabs, so that the excitability of parent crabs is at a higher level; the worse the quality of parent crabs is, the higher the mortality rate will be, and the number of eggs will decrease greatly. the quality of eggs is also very poor, and there are often serious dead eggs. 1. The choice of overwintering pool. Parent crabs generally spend the winter in outdoor soil ponds. Overwintering ponds should be chosen in places where the wind is sunny and close to the water source, where the environment is relatively quiet, east-west, rectangular or square, with a water depth of more than 1.5 meters, and the soil quality is better with mud, sand or clay. 2. Water quality control. During the overwintering period of the parent crab holding eggs, when the water body is frozen, insert an appropriate amount of grass handle, and break the ice every morning before the sun rises to clear the snow on the ice in time. The key point is to keep the water environment relatively stable. The main water quality indexes are monitored every half a month. The salinity is about 25 ‰, the dissolved oxygen is above 5mg/L, and the pH value is 7.8-8.7. The leaking earth pond should be filled with water every 5-7 days, and the amount of water should not exceed 30% of the total water body each time, so as to keep the water level above 1.5 meters. When it reaches more than 5 ℃, fresh sea water should be added and replaced regularly. Because although the development of parent crab eggs (embryos) is very slow and there are few metabolites when the water temperature is above 5 ℃, the metabolic ability of parent crabs begins to be enhanced, coupled with the higher density of parent crabs, the water quality will gradually become worse, which will affect the embryonic development of parent crabs, so it is necessary to adjust the water quality at this time. 3. Feed. Choose fresh bait with rich nutrition, such as sand silkworm, fresh mixed fish, etc., after parent crabs hold eggs, with the continuous change of water temperature, depending on the feeding situation of parent crabs, the daily feeding amount is generally controlled to 2-10% of the total body weight of parent crabs. No matter how the surface water temperature changes, as long as the parent crabs are found to be active, they should be fed properly. Feed once a day before sunset, put the feed below the water level along the soil pond, patrol the pool the next day to check the feeding of parent crabs, remove the residual bait, and adjust the feeding amount at the same time. Multiple kinds of bait should be fed alternately. Fresh bait and compound bait should be fed when the water temperature is above 8 ℃. When the water temperature rises above 8 ℃, the embryo of the parent crab begins to accumulate temperature, the development speeds up gradually, and the physical energy consumption of the parent crab increases. First, the parent crab constantly fan the tail fan to make the water flow around the embryo, remove the metabolites to get dissolved oxygen, and promote the development of the embryo; second, the parent crab may constantly secrete a kind of "maternal hormone" to protect the normal development of the embryo. At this time, in addition to regulating the water quality, it is also necessary to increase the feeding of some fresh bait and good quality compound bait to meet the physiological needs of the parent crab and ensure that the parent crab has sufficient nutrition and physical strength to reproduce. 4. Daily management. Patrol the pond once a day in the morning and evening to observe the activity, feeding and water color changes of parent crabs, check whether the escape prevention facilities are damaged, and regularly examine the development of fertilized eggs of parent crabs every half a month. timely take and adjust management measures to ensure that parent crabs can survive the winter smoothly. Fourth, the main points of adult crab production after the disaster: 1, pond cleaning. The pond must be cleaned up before the crab is released, and the pond should be strengthened after snow to remove too much silt. Crab species about 15 days before stocking, thoroughly clear the pond, there are dry method and with water to clear the pond two kinds. The general dry cleaning pond uses 1000 kilograms of quicklime per hectare and sprinkles it all over the pool after melting. The clear pool with water can only be used when most of the water cannot be discharged, and the specific dosage can be flexibly controlled according to the depth of the pool water, which can ensure that the enemy organisms in the water can be killed. 2. Reinforce and repair escape prevention facilities. Strong anti-escape equipment must be built around the breeding pond to prevent the crab from escaping. The inner wall of anti-escape equipment should be smooth, such as plastic film, iron plate, aluminum plate and so on. 3. Anti-freezing of aquatic plants. Some farmers have planted seaweed and other aquatic plants to prevent them from freezing to death when frozen after snow. the specific method is to ensure that the water level is higher than the aquatic plants, so that the ice layer is above the aquatic plants. 4. The breeding of crabs should be suspended. When the temperature is below 0 ℃, crab species can not be caught, transported or released to prevent frostbite. Wait for the weather to warm up, when the temperature is above 0 ℃, then carry on the related operation of crab species.