According to the author's practical experience, Penaeus vannamei (hereinafter referred to as white prawns) will experience reduced feeding and slow growth when the water temperature is lower than 18°C, and gradual death will occur when the water temperature is lower than 12°C. This phenomenon is common and serious in the wintering of white prawns in high density earth ponds. At the same time, the water environment in the winter shed is difficult to control, white prawn disease is frequent, the growth rate is too slow, and even the overwintering culture fails. The author combines the production practices of farmers and the common problems in the cultivation of white prawn in the winter shed. The following notes on the rearing of white prawn in winter sheds are presented below: Tips for fertilizers and waters 1. Special aquaculture special fertilizers for promoting the growth of fine unicellular algae Fertilizer, the former such as beneficial algae nutrients, algae extract, unicellular algae growth hormone and so on. Fertilizers commonly used are urea, ammonium bicarbonate, and phosphate fertilizers. Fertilizer should pay attention to keep the ratio of nitrogen to phosphorus 3-4:1. 2. The use of beneficial microorganisms on the same day or every other day, the effect of which is: on the one hand, the superior algae phase is rapidly propagated and a good water color is created; on the other hand, beneficial microorganisms form dominant populations in shrimp ponds, and the growth of pathogenic microorganisms is inhibited. A safe and stable water environment will help improve the survival rate of shrimp seedlings. 3. Appropriately opening the aerator in the process of fertilizer and water can speed up the speed of fertilizer and water and shorten the time for fertilizer and water. Disadvantages of using organic fertilizer and water alone: ​​(1) The fermentation process of organic fertilizers is not easy to control, especially when the temperature in winter is low, fermentation of organic fertilizers is often incomplete, and harmful organic pathogens cannot be effectively killed, leading to cross-infection. (2) The simple use of organic fertilizer can make macromolecule algae (Microcystis, etc.) grow too fast in water, and indirectly inhibit the growth of unicellular algae, which is suitable for the growth of white shrimp. Water quality management Because the winter shed is relatively closed, the water environment in the winter shed, such as temperature, atmospheric pressure, and illuminance, is very different from the natural environment. Therefore, the pH of the water body is stabilized, and ammonia, nitrite, hydrogen sulfide, and other harmful substances are reduced. Maintaining the growth of the fine algae in the water and maintaining the stability of the water color is the key to the successful wintering of white shrimp. The method of maintaining the stability of the water environment is based on regular (7-10 days) application of beneficial microorganisms to regulate water quality, appropriate use of biocides such as procyanidin, unicellular algae growth hormone depending on changes in water quality, and promotion of beneficial algae and beneficial flora. Reproduction inhibits the breeding of harmful microorganisms. At the same time with the use of multi-effect improver, accelerate the degradation of organic waste, reduce the content of toxic substances, activate shrimp pond bottom, and maintain the stability of water quality physical and chemical factors. During the cultivation of white prawns in the winter shed, darkness or turbidity often occurs. This is due to the lack of trace elements necessary for the growth of certain algae in the water, the inability of algae to grow normally, and the occurrence of algae aging and death. Where conditions permit, proper water change is a way to effectively improve water quality. However, due to the large difference between water temperature and water temperature in the shrimp pond, the exchange of water easily causes a strong stress response to the shrimp. Therefore, in this case, beneficial microbial preparations and multi-effect sediment modifiers should be promptly applied to remove as much as possible suspended organic matter in the water as soon as possible, to degrade the organic waste at the bottom of ponds, and to increase the number and flora of beneficial microorganisms in shrimp ponds. Through the heterotrophic action of beneficial microorganisms, it breaks down and absorbs too much organic matter in the water, reduces the toxicity of ammonia nitrogen, nitrite, etc., and maintains a good water environment. Under normal circumstances, the use of beneficial microbial preparations once every 5-7 days during overwintering can have a significant effect in preventing this phenomenon. Feeding and management 1. High-quality, high-energy, high-quality white shrimp feed should be used. Feed specifications increase with shrimp body growth. Put 3-4 larvae in a shrimp pond, regularly observe the feeding and growth of the shrimp, and determine whether or not the larvae have residual baits, the degree of fullness of the shrimp stomach, the number and length of the shrimp manure, and adjust the amount of feed to be fed. To not waste too much feed, but also to ensure the normal growth of shrimp. Due to the lower water temperature, the activities and metabolism of shrimp are at a relatively low level, and the demand for feed is also reduced accordingly. The principle of small meals should be adhered to when feed is fed. Feeding three times a day is appropriate. Because of the small amount of feed, only one feed a day. 2. In order to increase the growth rate of prawns in the early stage of culture, some prawn prawn feeds may be properly fed, and vitamin C, fish oil, immune polysaccharides, GD life factors, etc. may be added at the same time to strengthen the metabolism of prawn, increase the energy supply, and reduce the loss of protein. 3. The feeding of feed was finished within one hour, and 70% of the shrimp was full stomach. Too much feeding will not only increase the cost of breeding, but also increase the residual bait at the bottom of the pond, pollute the water body, and accelerate the aging and deterioration of the bottom of the pond. The proper use of aerators in aerobic aeration winter aquaculture is one of the keys to successful breeding. At present, most aerators used in shrimp ponds are impeller type and waterwheel type aerators. Deep-water aerators are not widely used because of the high prices, unstable use effects, and the constraints of the quality and life of the aerators. Since the air pressure in the winter shed is low and the air does not circulate, the oxygenation efficiency of the impeller type and water wheel type aerator is not high, and the aerator is often turned on for more than ten hours a day, and there is also a phenomenon that the shrimp lacks oxygen. The correct method is to use the oxygen at the bottom and use the oxygen on the surface of the water to use oxygen at the bottom. This can provide more oxygen to the bottom of the shrimp pond, which is conducive to beneficial microorganisms to form dominant populations, inhibit the breeding of anaerobic bacteria, thus ensuring the stability of the water environment and speeding up the growth of shrimp. In addition, in sunny days when the light is strong and the air temperature is high, both sides of the ventilation openings lift convection to absorb fresh air, convective air, do not let the environment inside the winter shed long-term low pressure, resulting in shrimp stress. Prevention and control of shrimp disease in winter shed culture of white shrimp, shrimp disease prevention and control is a very important part of the whole process of cultivation. The prevention and control of shrimp disease focuses on prevention. Due to the constraints of shrimp's physiology, living habits, and feeding habits, it is difficult to cure once the shrimps have developed shrimp disease, which makes it even more important to prevent shrimp diseases. The prevention of shrimp disease adopts comprehensive prevention and treatment, and the principle of treating it in emergencies, treating the symptoms in the absence of symptoms, and treating both symptoms and symptoms. Methods to ensure the stability of the water environment, good, improve the immune resistance to shrimp, the rational use of drugs and biological agents as the main comprehensive control measures to ensure the healthy growth of shrimp to achieve the purpose of preventing shrimp disease. 1. Regularly check the physical and chemical condition of water. During the whole culture process, the water temperature is maintained at 20-26°C, the dissolved oxygen is not less than 5 mg/L, the transparency is 20-30 cm, and the pH is 7.8-8.6. It is very important to monitor the pH of the water during the cultivation process. Under normal circumstances, the pH value will change 12-16 hours before the change of water, and the fluctuation range is greater than 0.5, while the change of ammonia nitrogen and nitrite will be delayed until the ammonia nitrogen, nitrite and other indicators are detected. The shrimp has been damaged. Therefore, the pH should be monitored periodically every morning and evening and recorded for future reference. 2, at any time to check shrimp feeding, shrimp excrement, gastrointestinal fullness and shrimp growth. Instantly adjust feed intake. Adhere to the use of high-protein, high-energy, high-quality, full-price compound feed, and avoid the use of low-protein, low-quality, low-cost feeds. Adhere to a small number of meals feeding method, the number of feeding 3 times / day is good, less feed in the morning, feeding the amount of the whole day of feeding 25% -30%. Feed more in the afternoon or at night, feeding 70%-75% of the total feeding amount. 3. Regularly add vitamins, garlic pulp, immune polysaccharides, GD life hormones, fish oil and other nutrients in the feed to improve shrimp immune resistance and promote healthy growth of shrimp. 4. Regularly release biological agents such as beneficial microorganisms and multi-effect sediment modifiers to improve and regulate water quality and sediment quality, and maintain the stability of the water environment. The water color is “cool, tender, and live†and provides a good living environment for the growth of shrimp. 5. Under normal circumstances, it is best to use less or no disinfectant. If disinfection is necessary, disinfectants with small irritant, low oxygen consumption, and strong bactericidal and antiviral effects should be used, such as dibromohydantoin, bromochlorohydantoin, tetrabromohydantoin, and long-acting chlorine dioxide. Minimize the use of disinfectants that enhance the "oxygen bond." 6. Once a shrimp disease occurs, ask an experienced technician to identify the cause and apply it to the patient. Do not use disinfectant drugs for a long time and in large doses. The use of drugs should have a certain interval of recovery. The treatment should be combined with the use of vitamins, immune polysaccharides, etc., to maintain adequate nutrition of shrimp, improve shrimp vitality, reduce drug stimulation of healthy shrimp. 7. Put a small amount (3-4 tails/mu) of omnivorous fishes in shrimp ponds to allow the fish to swallow sick shrimps and dead shrimps, and reduce shrimp outbreaks and exacerbations caused by self-mutilation of shrimps. Using an ecologically balanced approach, an ecological barrier is established between diseased shrimp and healthy shrimp. In summary, the overwintering culture of P. vannamei in South America is a complex systematic project. The key to healthy culture lies in the delivery of high-quality and healthy shrimps; the use of complex beneficial microbial agents to maintain a good water environment; and rational feeding of high-quality full-priced fish Improve the dissolved oxygen content in the water; improve the shrimp bottom sediment immediately, reduce the burden on the bottom of the shrimp pond; properly add the additives that strengthen the shrimp immunity and reduce the stress response; scientifically and rationally apply drugs to control shrimp disease. The use of beneficial microbial preparations to regulate and maintain a good water environment throughout the whole process of breeding is the key to successful breeding. It is also wintering aquaculture is a complex system engineering, the emergence of various anomalies in the breeding process must be handled by a comprehensive approach to management, a single method can only be an emergency, can not solve the underlying problem.
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