I. Requirement of prawn on the environment (-) The requirements for temperature and salinity of P. monodon and P. vannamei are well known. Both of these shrimps are warm and tropical. Subtropical shrimp. They are also salty. No matter how "wide" it is, there is a certain range of the most suitable scope. See Table 1 for details. Only in the most suitable range can shrimp grow healthily. Otherwise, it will grow well or be susceptible to disease. (B) The importance of water temperature to the health of prawn In the past few years, the warm winter, early spring urging early shrimp farming, coupled with some shrimp farmers in the shrimp market in the morning, selling good prices, early psychogenesis drive, raising the shrimp season more The earliest, even on the Zhanjiang lunar calendar month put the seedlings raising shrimp, they hold the "stroke" mentality, as long as the fight, they can make a fortune. Some people have achieved their goals and have stimulated many people to raise shrimp early. This has generally delayed early-stage seedlings by about one month. At this time, the temperature is highly volatile and extremely unstable. According to the laws of meteorological change in Guangdong for many years, there was a strong cold air intrusion around the beginning of March of each year. Even though the coast of western Guangdong, the temperature dropped to around 10°C. Before this time, the shrimp seedlings were not frozen and their growth was greatly inhibited. The juveniles were of weak constitution and could not withstand the sudden change of water temperature. When the external environment changes, these young shrimps bear the brunt of getting sick first. Late planting was too late, and in mid-and late October, white-spotted prawns or white vannamei were still released. At that time, the shrimp pond water temperature had dropped to about 20°C, and the diurnal changes were large. Moreover, the water temperature continues to drop, and it is impossible to reach the optimum temperature for the growth of these two kinds of shrimps. The growth is not normal and shrimps will die of illness over time. In the early morning and late evening of 1999, the shrimp culture became more and more sick. The main reason was that the shrimp pond water temperature did not meet the physiological requirements of shrimp, and the cultured shrimps were highly susceptible to illness. In addition, the water temperature of the cultivated shrimp grows parabolically, and the rainfall is adequate, the salinity is moderate, and the external conditions are suitable for the growth of the shrimp. Therefore, the shrimp will be smooth and the disease is small. Second, the unfavorable factors of shrimp aquaculture (-) Qingchi not complete, long-term overload of shrimp ponds shrimp expert aquaculture advisory group has long pointed out that in order to make sustainable development of shrimp, shrimp ponds up to two years of raising shrimp. However, on the coast of South China, some raise the shrimp production efficiency by 3 to 5 years. When the shrimp ponds are overloaded, the shrimp ponds do not have time to rest, and even the shrimp ponds do not have enough time to disinfect the shrimps. Therefore, shrimp disease frequently occurs. (2) The salinity of seawater is relatively high, and unfavorable shrimp growth will cause less rainfall in the early spring or late autumn. In particular, the coastal areas of Zhanjiang often suffer from drought. Shrimp ponds have high seawater salinity, and the salinity is generally above 5/1000, which exceeds the optimum salinity of 10 to 20%o of the two shrimps. The growth is slow with the growth of the oyster shell, and the water temperature is low. It is even slower. When the external environment changes rapidly, these shrimps are susceptible to death. (3) The water temperature is low, and it is not appropriate for the food organisms to grow in the early spring or late autumn. The water temperature is low, the salinity is high, the food organisms grow slowly, the water color is difficult to cultivate, and the feed growth of shrimp ponds is the optimum water temperature 25-30 degrees Celsius, in salinity. In the low-salinity seawater of less than 20 parts per thousand, there are many kinds of food organisms and the population is large, so that the shrimps are rich in natural food organisms, close to the natural ecological conditions, the shrimps grow well, the feed coefficient is low, and the shrimp bodies are robust and resistant to diseases. Strong. Third, grasp the season of shrimp farming, implement the technical measures for healthy shrimp farming Guangdong coast all over the spring temperatures vary, the normal climate, the correct time for seedlings, water temperature can be stable above 22 °C, in the coast of Zhanjiang is around March 20 . The Pearl River estuary will reach the end of March. The east coast of Guangdong will not reach this temperature until mid-to-late April. At this time, after the shrimp seedlings are put into the shrimp pond, the water temperature is suitable, the growth is fast, the shrimp body is robust, and the disease resistance is strong. Prawn Penaeus monodon and P. vannamei have similar habits. They like to grow water with higher water temperature and lower salinity. As long as they meet their ecological conditions, they have proper technical measures and can obtain ideal breeding results. The following links should be specifically addressed: ) Thorough cleaning and disinfection is an important part of prevention of shrimp disease (2) Pre-flushing of food organisms and preservation of good intercropping water (C) Selection of healthy and robust shrimps. About the equivalent of 1.2-13cm shrimp seedlings grow. According to Song Yuchang (1996), after the P.20 shrimps, lymphoid organs grew rapidly and their ability to resist diseases increased significantly. However, the shrimps are too large, the seedling pools are less water-changing, the density of the shrimps is high, the water in the pools is not clean, and bacteria are often present, and the growth is inhibited, which is unfavorable for the growth. In the production of shrimp seedlings, Changchi water temperature is high, the external ecological conditions for shrimp growth, shrimp can be smaller. (4) Feeds of high quality and sufficient quality should pay attention to the cultivation of basic foods and feed in advance in time. Some old-fashioned shrimps believe that the food organisms in shrimp ponds can meet the growth requirements of young shrimp and do not feed them in time, delaying the growth of shrimp. Under normal circumstances, shrimp and man-made land, after 3-5 days to feed fish and shellfish steamed into cakes with eggs, filtered with a 20-mesh sieve, even into the pool, its nutrient-rich, close to shrimp or natural waters The bait, larvae grow fast and healthy. About a week after the cake was used, it was transferred to feed No. 1 shrimp. With the growth of shrimp, replace other specifications of feed. Feeding requires a small amount of meals, and the amount of feed should be based on various considerations such as the amount of food consumed by the shrimp, the climate, the quality of the water, and the growth of the shrimp. Shrimp full, no waste, to maintain good water quality, bottom quality, control feed coefficient, feed to use high quality brand, a few brands alternately or mixed use, you can get nutrition complement, so that the shrimp grow fat and grow quickly. (e) Do a good job in water quality management. In the first month of shrimp farming, fertilize regularly to regulate water quality. During the shrimp farming period, keep the pool water “green water†or “yellow brown waterâ€. Transparency 30-50cm. The introduction of freshwater or semi-closed shrimp farming, regular or irregular lime application, and the adjustment of pH are the guarantees for the success of seizing shrimp. (6) Use of aerators It is important to promote the oxidative decomposition of organic matter in the shrimp ponds, to promote up-down convection of the pool water, and to increase the bottom layer for dissolution. Treating shrimp at the onset stage of shrimp disease, feeding oxygen, reducing the underlying hydrogen sulfide, ammonia and other harmful substances, improving the secondary medicine feed, and preventing the occurrence of shrimp disease is an effective measure of the ecological conditions of shrimp habitat, improving the physical fitness of shrimp. Shi. Strong vitality, promote shrimp growth, increase shrimp production. (7) Actively preventing and treating shrimp diseases During the cultivation period, disinfectants containing chlorine shall be applied to the shrimp ponds regularly or from time to time to disinfect the shrimp pool so that the number of bacteria in the shrimp ponds is controlled below 100,000/Ml in order to inhibit the breeding of harmful bacteria. The beneficial bacteria, such as photosynthetic bacteria, probiotics, probiotics, and methotrexate, are applied several times in the shrimp ponds each month to make the beneficial bacteria dominant and suppress harmful bacteria. This is an effective method for preventing shrimp disease. At the same time, combined with the degree of pollution in shrimp ponds, appropriate application of zeolite powder or dolomite powder to regulate water quality and sediment quality. The proper deployment of VC, polysaccharides, and fish oil in the shrimp feed will improve the utilization of the feed and increase the immunity of the shrimp. It is an effective measure to prevent the occurrence of shrimp disease by administering a medicine feed in the case of shrimp disease during the onset of shrimp disease. The results of the cultivation of P. vannamei in Guangdong are not as strong as the imagination, and the disease in the second half of 1999 was the same as white spot disease. According to reports in Taiwan, the disease caused by Taiwanese breeding of P. vannamei in the first half of 1999 was very serious. Penaeus vannamei is cultivated in South America. Taura virus disease is very serious. It is the third killer virus (after white spot virus and yellow head virus). Therefore, the cultivation of Penaeus vannamei should take a cautious approach, prevent it from proceeding in a nutshell, explore the experience of breeding, and gradually proceed, so that the shrimp industry can continue its healthy development.
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