Once the river crab is infected, the infection spreads very quickly, and some diseases deduct “shaking disease†basically is incorrigible. The farmers have suffered heavy losses. Many crab farmers have already reached the point of “looking at the disease and sigh†and are afraid to raise crabs again. Some of the crab farmers have adopted artificial ecological farming and have experienced less incidence in the past years. The cultured crabs have large specifications, good quality, and considerable benefits. For this reason, I believe that the development of crab farming in the future must take the path of ecological crabs. First, attach importance to the conditions of the water crab in the natural environment, disease resistance is strong, but in the case of intensive farming, due to the high density of farming, limited range of activities, coupled with feeding and management method defects, easily lead to crab disease. Therefore, it is very important to choose what kind of water conditions. Water area is the basic condition for the growth and culture of crabs. Currently, there are many kinds of crab waters, including ponds, ditches, lakes, reservoirs, rice fields, floodplains, and shallow rocks. From the effect of raising crabs, larger areas of lakes and shoals are considered. It is better to raise crabs in paddy fields, and crabs in small ponds are not good for crabs. Generally, water area with an area of ​​more than 50 mu, good soil texture, rich natural food, water quality, no pollution, good light and good ventilation conditions is the best choice for raising crabs and raising high quality crabs. Cultivate crabs to match them. Second, attach importance to the quality of crab species The quality of crab species, including the choice of pro-crab, the quality of crab seedlings big eye larvae, the cultivation of crab species "duck crab" and many other aspects, must be fastened around. The pro-crabs are fundamental. At present, except for a few nursery units, the pro-crabs originate from natural fishing in the Yangtze River. The vast majority of them are simply selected from the culture area, resulting in mixed crab species in different river systems, small individual crabs, and severely degraded germplasm. This has become a major constraint to crab farming. For crab growers, the first choice is to look for the source and specifications of the crabs. It is best to take the pro-crabs from the Yangtze River or use the crabs from the Yangtze River crabs to cultivate the crabs. Breeding crabs grow crabs. During the breeding of crab seedlings and the cultivation of crabs, the large number of seedlings that use drugs often cause damage to organs of the crabs, especially the liver, lose their ability to resist disease, and are drug-dependent and drug-resistant. Aquaculture crabs are extremely harmful and special attention should be paid to this “drug vaccine†when purchasing crab seedlings. In addition, sexually mature, long-distance trafficked crabs, such as polyhelminths and crab slaves, cannot be stocked as crabs. When stocking, crabs should be immersed and disinfected. The use of drugs, dosage, and immersion time must be properly controlled. It is necessary to prevent effects and to prevent poisoning or death. Third, pay attention to reasonable stocking to determine stocking density and polyculture should first consider the prevention and treatment of the disease. A great deal of experience has shown that adopting a rare-raising approach not only improves the proportion of large-size and high-quality crabs, increases the benefits per unit area of ​​water, and promotes ecological balance, but also regulates the microecological balance, maintains normal flora in aquaculture waters, and prevents infections. The role of epidemic outbreaks. Reasonable stocking densities and polycultures are actually to maintain a reasonable density of crabs in a limited space, which can reduce the chance of pathogenic contact and infection. In addition to good environmental conditions, crabs with rich experience can be properly intensively bred; large water bodies should be semi-intensive or extensively cultured depending on the specific circumstances. From the point of view of controlling the outbreak of crab disease, the number of crabs for crabs on the surface of each hectare should not exceed 18,000, ie 1,200 per mu. The surface of crabs can be mixed with filter-feeding eel and squid, together with a small amount of small-size eel and large-sized eel, to feed plankton, wild fish, and control blue mud in crab water bodies. Fourth, pay attention to planting aquatic plants commonly known as "crab size, see water plants." Aquatic grass is not only a delicious feed for crabs, but also an attachment for crabs in the water. It is also a hiding place for crabs and clam shells. Water plants also increase dissolved oxygen, regulate water quality, and lower water temperature, especially to adsorb water and soil fat. . The plants in the crab ponds should be submerged, emerged, and floated to form "underwater forests" and "water peanut clusters." Submerged aquatic weeds are preferably Yinleza, Vallisneria, Malanian, and alfalfa. Aquatic aquatic plants include reeds, barnyardgrass, etc. Floating aquatic plants include water peanuts, leek, and duckweed. Before the crabs are stocked, they are planted, transplanted, and transplanted to grow and plant their feet. During the rearing period, if some aquatic plants or tender stems are eaten by crabs, they must be replenished in time to keep the water body covered with 2/3 of the grass. rate. Fifth, attention to the use of snails crab shellfish especially snails particularly like to eat, because snails are rich in nutrients, but also contains more of the crab development of calcium, phosphorus and other substances, so when processing crab mixed feed must add snails Meat acts as a food attractant. Spirulina is not only a good natural bait for crabs but also an excellent “cleaner†in crab ponds. It helps to improve the bottoms and improve the self-purification of water bodies. The use of snail has two methods: First, fresh snails will be directly put into the crab waters in spring to allow them to feed plankton in the water and naturally reproduce snails. Small snails are fed by small-size crabs. Large snails feed on large crabs. According to the feeding conditions of crabs, they are not regularly supplemented. They always keep live snails at a certain density in crab ponds. Second, they use crumbled snails during the middle and late breeding period. The meat is mixed with other vegetable feeds to feed crabs. Sixth, pay attention to the regulation of water quality Maintaining good water quality is particularly important for healthy crabs. It generally requires fresh water, dissolved oxygen above 5mg/L, pH value between 7.5-8.5, and the principle of maintaining water level and adding water is “Spring shallow, "Shaman, Qiuqin and Dongshen"; The transparency of water is gradually increased from 30cm in early spring to 45cm in summer and autumn. If the water has a certain degree of fatness, the water level should be appropriately shallow, and it can generally be controlled at 0.4-0.6. m, transparency 30cm-35cm; medium water depth, 1m-1.5m, water is not fat, transparency 35cm-40cm; late water to clear, transparency 45cm. Adding water or changing water is currently the most common method for improving the water quality environment and preventing diseases. However, because of the imbalance of the ecological environment, the physical and chemical factors in water and the pesticides remaining in the water exceed the standards, the scale of crab cultivation continues to expand and the area of ​​the breeding area is contiguous, and most of the ponds enter into the area. Drainage is not separated, resulting in the exchange of water for the "good water" situation, often increase the number of water changes and water changes and crab did not reduce, but increase and increase the strange phenomenon. Therefore, the addition of water and water to crab ponds should be based on the water quality, water temperature, season and crab growth. The water quality of crabs is treated with self-pure grasses, snails, photosynthetic bacteria using beneficial bacteria, probiotics, and disinfectants. This maintains the benign ecological circulation of waters and promotes the healthy growth of crabs. Seven, pay attention to scientific feeding and feeding a comprehensive nutrition of high quality feed, try to meet the nutritional needs of crabs, keep the crabs nutritional balance. Scientific feeding can not only enhance crab's physique and disease resistance, but also prevent water quality from deteriorating and reduce the occurrence of crab disease. Feeding should be based on the season, weather, water quality, and feeding conditions during the growth stage of crabs. Specifically speaking, the first is to have a reasonable mix of barnyardgrass, sperm, and green fodder, both to prevent crabs from suffering from undernutrition and prone to soft-shell disease, and to prevent excess nutrients from easily causing clam shells to fail. General implementation of "two fine, medium thick" feeding method. Second, the amount of feeding should be appropriately increased or decreased according to the amount of crabs in the water, the quality of the feed, and the eating and feeding conditions of the crabs. In addition to meeting the supply during the period before and after, the medium term should be properly controlled. Third, the feed must be of high quality and fresh, and avoid feeding decomposed feed and animal carcasses. Eight, pay attention to the use of drugs in order to control the occurrence of crab disease and the treatment of crab disease, some crab ponds commonly used water disinfection method to kill bacteria, parasites, and some even half a month or once a week, this method is certainly a certain The effect, but also kills most of the beneficial bacteria at the same time, impedes the decomposition of organic matter such as residual baits and feces in the water, indirectly increases the pollution of water quality, reduces the disease resistance of the crab, and some drugs also have Strong toxic and side effects cause organ damage. This method of achieving temporary sterilizing and killing at the expense of the health of crabs and the destruction of the aquatic ecological environment is inadequate. Therefore, it is advisable to use as little or no medicine as possible. It is best to use Chinese herbal medicines, medicines that have little impact on the health of crabs, and medicines that protect the liver and other organs. Avoid using drugs for humans and prohibit the use of antibiotics in excess. The drugs used must master their acid and alkali properties and incompatibility. When the crab is attacked, it is necessary to consult an expert on crab disease, accurately diagnose it, prescribe the right medicine, try to reduce the number of times the water is poured on the drug, and do not use it frequently. The purpose of inhibiting and killing pathogenic bacteria in the crab can be achieved by feeding the crab on the bait. When making baits, be careful to mix evenly. It is best to use adhesives.
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