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Healthy and practical management technology of cultured shrimp
First, the site selection 1, the water supply conditions shrimp production must have sufficient water and good water quality as a guarantee, which pH and salinity of these two parameters can not be excessive fluctuations, the ideal pH range of 7.5-8.5 The salinity is between 10-30 。. In addition to brackish water and brackish water, the production of freshwater sources in shrimp farms is also very necessary. It can adjust the salinity of shrimp ponds and the domestic water supply for shrimp farmers. The water source shall not be affected by industrial and agricultural sewage discharge. The main water quality indicators shall not exceed the safe concentration required for shrimp aquaculture and the national fishery water quality standards. 2. Geological conditions There is a muddy or muddy sandy intertidal zone with less wind and waves along the coast, and a saline-alkaline wasteland along the tidal zone. However, it is necessary to make more explorations of the bottoms and analyze the chemical composition and mechanical composition of the soil samples at different levels. Try to avoid building pools in acidic soils. In addition, attention should also be paid to the choice of flat terrain, convenient construction and drainage. 3. Social conditions (infrastructure) Transportation, electricity, communications, labor, feed and supply, security and other social and economic factors should be considered. Second, shrimp farm construction 1, shrimp ponds. The area of ​​the shrimp pond is about 10 mu. The shrimp pond is preferably round, and square and rectangular shrimp ponds and quadrangular arcs are also the pools that effectively circulate water. Pool surface depth 1.5-2.0 meters. The bottom of the pool should be turned down towards the drain gate with a ratio of 0.2%. The top of the pool levee is 2-3.5 meters wide, and the top of the levee is 0.5-1.0 meters above the design water level. The slope of the bottom of the pool depends on the soil quality and slope protection. Generally, the slope is 1:2-1:2.5. The clay land generally does not need slope protection, loose soil or dams at both ends of the long pool are best for slope protection. Both ends of the shrimp pond should be provided with a water gate. Gate width 1.0-1.5 meters. The bottom of the drain gate should be lower than the deepest point in the pool so as to drain the pool water, which is beneficial to clearing the pond and collecting shrimp. There are three gates on the gate wall, gates are installed in the middle, and gates are installed inside and outside. The inlet and outlet channels should be set separately. The inlet and outlet should be kept as far away as possible, and the drainage and the inlet water should not be mixed. Wastewater should be treated (sedimentation tank) before being discharged from the shrimp farm. III. Preparation before laying seedlings 1. Dredging. After the shrimp is harvested, the pool of stagnant water shall be drained, the sun bathing pool closed, the dams and gates repaired, and the sludge in the pool shall be completely removed. Wherever there is thick sediment, human or bulldozers and mud pumps are used to completely remove the sludge. The beach with less sediments can be used to promote the oxidative decomposition of organic matter by methods such as exposure, ploughing, and rinsing, and it should be repeatedly poured and discharged several times before being discharged. Thoroughly dip the bottom of the pool. 2, remove the algae. The breeding ponds are rich in a large number of algae and aquatic plants. The most common species are Cladophora, Brassica oleracea, Gossypium arborescens, and Large-leaf Algae. They occupy the pond space and wind the shrimps, causing the death of shrimp or young shrimps. They also strongly absorb the nutrients in the water and hinder the reproduction of shrimp food organisms such as plankton, benthic diatoms, and so on. Especially when these algae bloomed to a certain extent, they began to die in large numbers, damaging pool water and causing a large number of shrimp deaths. Therefore, any pond that has a large population of algae should be cleared before stocking. Removal methods are generally to remove the algae out of the pond before stocking, or to use ploughing to bury the algae in the mud. There is also a point of burning the dead algae after drying. It is also possible to use early fertilizer methods to limit the breeding of heterotrophic algae, that is, fertilize immediately after irrigation to allow plankton to reproduce first, reduce the transparency of the pool water, and suppress the germination of algae buds. 7-8 ppm copper sulfate and 0.5 ppm moss algae can also be used to suppress the algae. 3. Apply lime. The lime should be applied immediately after the pond is drained with clean water. The lime used at this time is agricultural lime (CaCo3), and 75-150 kilograms of lime per acre should be spread over the bottom of the pool and up to the top of the dam. In the feeding area and the wet area of ​​the pond, the amount of lime sown should be increased. 4, clear the enemy. In the case of shrimp disease, ponds that do not drain water must also be cleared of predator organisms before applying lime. The medicines used are: Tea seed cake: The main kill fish, shellfish, sandworm, etc., and the tea seed cake will be used. Crushed, soaked in water for several hours, sprinkled in water at a rate of 15-20 grams per cubic meter of water, killing fish for 1-2 hours. Chlorinating agent disinfectants: including shrimp kang, bleaching powder and so on. They have a strong killing effect on protozoa and bacteria. The dosage of shrimp Kang is 2-3ppm and bleaching powder is 30-50ppm. Chlorine dioxide: Has the effect of killing bacteria, fungi, viruses, etc., dosage 5-10ppm. Ammonia: A high concentration of ammonia kills fish and pathogenic organisms, and has the function of fertilizer pools. The amount of 250ppm. Trichlorfon: Trichlorfon is highly toxic to crustaceans and uses it to kill white shrimp and other miscellaneous shrimps. Dosage of 2-2.5ppm, use of trichlorfon clear pool must be carried out 10 to 15 days before stocking shrimp, otherwise it will hurt the shrimp. 5, water and fertilizer. The purpose of influent and fertilizer water is to promote the healthy growth of plankton. Well-developed plankton is the basis for aquaculture production because of: - Avoiding pool bottoms and preventing the growth of harmful benthic algae. - Reduce fluctuations in water temperature. - Provide oxygen. ——Using nitrogen and phosphorus-containing waste in the pool. - Provides a darker environment that makes shrimp easier. After the initial sowing of lime is completed, the pond can be filled with 30-40 cm of water. The water should be filtered through a screen of 60 mesh or more into the pool, and then the fertilizer should be applied according to the pond's fertilizer status. It is better to use dry chicken manure in the new shrimp ponds, with 100-200 kilograms per acre, divided into 2-3 inputs. The old shrimp ponds are suitable for applying chemical fertilizers. The first application of nitrogen fertilizer is 2-4ppm, and phosphorus fertilizer is 0.2-0.4ppm. After that, fertilizer is applied once every 2-3 days, and the dosage is 1/2 of the initial dosage. And gradually add water to 50-70 cm. When the transparency of the pool reaches 30-40 cm, fertilization should be stopped. After the plankton reproduces, if the water becomes clear, it may be due to the breeding of protozoa such as caterpillars, salty Broad Bean insects, etc. In this case, the pool water should be drained and the water and fertilizer pool should be re-aligned. After the pond enters the water, it is necessary to sprinkle lime once more, and then put the seedlings. The purpose is to maintain the pH between 7.5-8.5 and the daily pH fluctuation is less than 0.5. The dosage is generally about 7 kg per mu. Fourth, shrimp stocking 1, stocking conditions 1 water depth should reach 40-70cm, fertile water, transparency 30-40cm. 2 The pond water temperature should be above 20°C. 3 Shrimp pond salinity is preferably maintained at about 20 ,, and the salinity difference with the nursery room is not more than 5 ‰. Otherwise, the shrimp seedlings should undergo a step-by-step transition so that they can be adapted and then restocked. 4 The pH should be between 7.5-9.0. 2. The selection of shrimp needs to be healthy, disease-free, with neat size, clean surface, agility and flexibility during swimming, shaking from time to time when the whip touches, and swimming backwards when the water is stirred. When the flow of water stops, healthy young prawn tends to come to the side, and little or no drugs are used in the nursery process, and high temperature cultivation is not required. 3. The seedling density of seedling density should be determined according to the water depth of the shrimp pond, the water exchange conditions, the type and amount of feed, the specifications of the seedlings, and the technical and management level. At present, the general water is shallow (about 1m), there is no aerator pond per acre seedlings of about 10,000, and set up aerators, water depth of about 1.5m ponds, per acre seedlings 20,000 or even 50,000 or so. 4. The cultivation of artificially cultivated shrimp seedlings in the middle of the shrimp seedlings is relatively small, and the survival rate is very unstable, which often affects the growth effect. After the middle-cultivated shrimp seedlings are stocked, the survival rate is high and stable, which facilitates the estimation of the number of shrimps in the shrimp ponds and accurate feeding. Since the density of the shrimp seedlings in the middle-cultivation period is relatively large, the density of other competing food-eating creatures is relatively reduced and the bait-feeding effect can be improved; The intermediate cultivation delays the rearing time of the rearing tanks so that the food organisms in the rearing tanks have more sufficient breeding time and growing time, which can enhance the effect of the cultivation of food organisms and reduce the breeding period in the rearing tanks. Therefore, the pollution of shrimp ponds is reduced, and it is beneficial to the growth of shrimp during the growing period. In addition, it is also advantageous for multi-culture shrimp. The practice is: to cultivate the pool can use the cultivation pool. It can also be specially built, with a water depth of 0.5-1 m. It is also necessary to clear the pond and reproduce plankton before releasing the seedlings. The methods are the same as before. Stocking densities are 10-15 million per acre. During the cultivation period, the live bait is better. In the initial stage, the minced fish and cake are used (the daily amount is about 10,000 to 500 grams), and the young shrimp can also be used. Feed (starting with a daily amount of about 10,000 100 grams). When the shrimp grows to 3-4cm, it can be divided into small groups. 5. Observing technicians in the growing process should inspect the ponds in the early morning and late afternoon to observe the environmental changes, safety conditions, and shrimp activities of the ponds and make records. The contents are as follows: 1. Measure the temperature and water temperature once every day at 5 o'clock and 15 o'clock; determine the water-soluble oxygen content of the pool at 6 o'clock and 16 o'clock; determine the salinity, transparency, pH value, and ammonia nitrogen of the pool water regularly or irregularly. And hydrogen sulfide content. 2. Pay attention to whether the gates and fences leak water and run shrimp. Pay attention to the danger of leaks, bursts, and flooding of the dams and find problems and timely maintenance. 3. Observe the activities and distribution of shrimp, pay attention to the health status of the shrimp, and check whether there is dead shrimp at the bottom of the pool and at the poolside. The length of shrimp was measured once every 5 days or 10 days. The length of the shrimp is the length from the base of the eye stem to the end of the tail section. The number of manoeuvres per measurement must not be less than 50. While measuring body length, stomach fullness was determined. According to the number of stomach contents, it is divided into four levels: full stomach, half stomach, residual stomach and empty stomach. If necessary, stomach contents should be analyzed. 4. Regularly estimate the number of shrimp tails in the pool. To provide basis for determining the amount of bait. For 2-3cm shrimps, small nets of known area can be used to lift the shrimp in multiple points in the pond to determine the number of tails per unit area of ​​prawn and thus to determine the number of prawn in the whole pond. More than 6cm shrimp. Rotary net quantification can be used. In the pool sampling, the total number of shrimp caught, using the following formula, find the number of shrimp in the pool. Total shrimp shrimp pond area (m2) Total pond tail number = K net mouth area (m2) Netting number K is the net mouth shrinkage factor, which increases with water depth, and the water depth at 1m is 2, 2 meters. A marker count can also be made later in the culture. According to pond size. Collect 500-1000 prawns at different sites, cut off one side of the tail and return it to the original pool. After 1-2 days, use nets to catch shrimp in different parts of the pond. Count the total number and the number of tails of the cut-down tail shrimp, and the number of re-catcher tails should be at least 1/10 of the total number of tails cut. Use the formula below to find the whole pond shrimp. Number of. The total number of shrimp shrimp shrimp tail = total number of shrimp re-capture flag shrimp tail number six, bait and feeding 1, bait species: Animal diet: under the miscellaneous fish. A small amount of low shellfish. Require disinfection or steaming after feeding. Formulated feed: It is based on the nutrition needs of shrimp and is made of various raw materials. The requirements are: protein content should be over 40%, of which animal protein should account for more than 1/3; crude fat content is 4-6%; carbohydrate 20 About 2%; minerals below 20%. Particle diameter 1.5-3.5mm, water content below 10%, smooth surface without bristles and cracks, soak in seawater for three hours. 2. The determination of the amount of bait The determination of the amount of bait is a key technology in the cultivation, and it is the main factor determining the success or failure of raising shrimp and the economic benefit. The number of baits is generally determined based on the following factors. 1 First, the number of shrimp tails in the pool should be accurately estimated. In addition to the above estimation method, the survival rate can be estimated based on experience. Based on the estimated number of shrimp tails and the average body length, the feed intake formula was used to calculate the number of feeds. The calculation formula for various baits is as follows: The average body length of shrimp is represented by I, and the unit is centimeters. The food intake unit is grams, which means that each shrimp feeds on a daily basis in grams. Shellfish and mixed fish (fresh weight) = 0.6612.5 Shellfish and mixed fish (fresh weight) Compound feed (dry weight) = 3 2 Feeding amount was adjusted according to the feeding condition of the shrimp. After 1 hour of feeding, 50% of the prawns should reach full stomach or half stomach. If there is no adverse change in the environmental conditions, 50% of the prawns should reach full stomach or half stomach. Conversely, if there is still excess bait in the pool before the next feeding amount, feeding should be reduced or suspended. 3 Adjust the feeding amount according to the environmental conditions. When the water temperature is too high or too low, the salinity changes abruptly, the dissolved oxygen is insufficient, and when the water quality conditions such as ammonia nitrogen exceed the standard, the food intake of the shrimp may decline. Therefore, in the event of poor water quality, every effort should be made to improve water quality and reduce or suspend feeding. 3. Feeding position: The ideal bait distribution is in areas where shrimp can feed as soon as possible. Shrimp tends to ingest food at the bottom of the clean pool cleared by aerators. Avoid scattering the bait in dirty areas. At the initial stage of breeding, the pond should be baited about 2 meters from the dyke. With the growth of shrimp, gradually feed into the deep water during the day and feed in the shallow water area at night. At the same time, the feeding should be uniform to facilitate the feeding of shrimp. 4, feeding time: the former mid-term vote 2-4 times a day, post-cast 5 times. Nocturnal feeding should account for more than 60% of the daily feeding amount. Mildew, deterioration, fat ammoniation (oil burning) feed cannot be cast. VII. Water Quality Management Survival of shrimp in water, water quality directly affects the physiological activities of shrimp. In fresh and high-quality water, the shrimps have a strong food intake and grow faster. Otherwise, it is the delivery of high-quality bait, shrimp does not ingest food, even due to lack of oxygen caused the death of shrimp. Therefore, to raise a pond, we must first raise a pool of water. 1. Water quality control index pH 7.5-8.5 Daily fluctuations Salinity 10‰-30‰ Daily fluctuations 80mg/l Hydrogen sulfide 0.01mg/l Transparency 30-40cm 2. Add water and change water in the early stage of cultivation. Add water to the deepest water level within 20-30 days, then change the water depending on the water quality, and change the water if the following conditions are required: - The difference in pH value is more than 0.5 or more than 7.5-8.5. - The water is too transparent (>80cm) or too turbid ( - the color of the water darkens significantly. - The amount of inorganic suspended matter increases.) - Stable foam appears on the surface of the pond. Measured to be exchanged before changing water Water pH, salinity and turbidity The water salinity should be similar, the pH is between 7.8-8.2, the water should not contain large amounts of suspended solids, conditional reservoirs can be allocated, and the water is precipitated in the reservoir for 24 hours. After adding water, even if the water quality is good, the amount of water changed per day should not exceed 30%. When fluctuating shrimp disease or prone to fulminant shrimp disease occurs in the vicinity, you should change the water as little or as little as possible. 3. Lime and its types of use include: Agricultural lime, also known as stone powder (CaCo3), is directly crushed by limestone to increase the buffer capacity of the pool water, and has no significant influence on the pH value of the shrimp ponds. In particular, the high-level pond raises the shrimp.Caustic lime (CaCoH2) is a kind of limestone that is burned by high temperature of about 800-900°C and then added water to it to explode into small particles.It is used to increase the pH value of the pool water and the amount is generally 4-6kg/mu. Should not be used. CaO), which is lime without water added after firing from limestone, has a great influence on the pH value and cannot be used directly in shrimp ponds. It can be used in ponds and clear ponds with low pH. Dolomite powder (CaMg (Co3) H2), which has the same effect as agricultural lime, and currently has a large amount of high-level ponds.In the production process, lime can be used frequently, and lime should be used if the pH value drops below 7.5 or the fluctuation is greater than 0.5 within 24 hours. It is often associated with a decrease in alkalinity, lime is added after each change of water and after heavy rain, and lime is added twice a week for the first 50 days of cultivation to stabilize the pH and ensure good growth of plankton. Dolomite should be used routinely.Slaked lime is used only to increase the pH when the pH is lower than 7.5. 4. Sulfide treatment Substrate pollution is the main cause of poor water quality. Protecting and properly treating the bottom quality is effective for improving the water environment. Method: In addition to the appropriate amount of feeding, the bait-reservoir and bait-cornered sludge bait should be frequently removed. When the sediment contamination is serious, iron oxides, slag, and zeolite powder containing iron oxide can also be added to the tank to avoid hydrogen sulfide. The production of high pool The use is 1-2 times per month in the early period of stocking, once every 10-15 days in the middle and later period, and the dosage is 80-200kg/mu.5. Add photosynthetic bacteria photosynthetic bacteria to improve water quality, sediment quality, control shrimp disease, and promote growth The special function is: In the first 2-3 days before the shrimp is put, 5 liters of bacteria liquid per acre is sprayed on the whole pond, and it is best to mix the photosynthetic bacteria with the fine sand and spread it to the bottom of the pool, every 15-20 days thereafter. Follow-up application 6. The aerator for aeration of conditional water in the pool water should be equipped with aerators, use 2-6 hours at night for every 2-3 days in the early stage of breeding, and use 2-6 hours for each night in the middle period, except for feeding at late stages. They are used after they are parked.8.Hazard Prevention and Pesticide Despite the clearing of the pond prior to the stocking of the shrimp, the cultivation period should still be noted: 1. Prevention of harmful plankton due to large amount of feed in the pool Fertilizers often have a large number of toxic or harmful plankton breeding during the development period, which has an adverse effect on the growth or survival of the shrimp. Toxic organisms mostly belong to the genus Dinophyta, such as N. dinoflagellates, noctiluca, etc. When they multiply, they not only consume large amounts of oxygen at night, but also produce toxins that cause them to paralyze and die. During the high temperature period in summer, rotifers and prawn are frequently bred in large numbers. They often eat phytoplankton in ponds, reduce the oxygenation factor in the pond, and increase the consumption of oxygen, resulting in the death of shrimp. 1-2ppm of copper sulfate can be used to kill noctiluca, rotifers and 70-80% of protozoa. The application should be carried out in the morning or at noon on sunny days. When the lobsters multiply, they can be killed by light. 2. The removal of fish often causes fish eggs or fry to enter the shrimp pond due to the rupture of the filter net during the irrigation process. Trash fish compete with shrimps for space, fight oxygen, and compete for bait. Fish kills shrimp. When fish are found to be large, tea seed cakes can be used for poisoning. The poisonous fish is selected in the morning during the tide. When poisoning fish, 1/2-1/3 of the pool water should be drained first. After that, the amount of shrimp pond water is accurately calculated. -20ppm injection, tea seed cake needs to be crushed and soaked in water, even after the water with the slag poured into the pool, the fish killed after 2-3 hours after application, remove dead fish, fresh water poured into the pool. 3. Do not apply pesticides when shrimp pecks. Nine, the common shrimp disease prevention shrimp disease during the growing season, once the disease, due to large shrimp pond area, water, drugs are often difficult to work. Therefore, we should focus on prevention and minimize the occurrence of diseases. The main prevention measures are: thorough clean pool disinfection; use of robust shrimp; reasonable control of stocking density; appropriate amount of high-quality feed, to avoid the use of mildew feed; strengthen feeding management, maintain a good bottom and water environment, water conservation, Do not blindly big row big irrigation; disease season, appropriate amount of feeding baits and the rational use of disinfectants or bottom modifier. The diagnosis and control methods of common diseases are as follows: 1. Symptoms of viral diseases: The symptoms are not obvious. The fulminant death may occur within 2-3 days after the incubation period. Observed with the naked eye, the disease did not ingest at the beginning of the disease, and the activity decreased and the response was sluggish. Some shrimps are pale red or gray, white or yellowish spots on the breastplate, and lentigos, hepatopancreas shrinking or swollen and erosion. Prevention and control: Currently, there are no effective anti-virus drugs for shrimp virus disease, which is mainly to strengthen feeding management and comprehensive prevention. 1 thorough cleaning and disinfection; 2 stocking of disease-free and healthy shrimps and control of stocking densities; 3 use of non-polluting and non-virus water sources. When a contagious epidemic is found, it is temporarily closed without changing the water. 4 In the epidemic season, 1-3 gram of poisonous venomous kings are added to the feed; 5 If the prawn is found to have a virus but has not yet developed, oxygenation measures should be taken. Ensure that the dissolved oxygen is not less than 5mg/l at any time; add 3‰ stable vitamin C and 1% shrimp virus to the net in the feed; 6 keep the shrimp ponds with stable environmental factors without disturbing people; 7 prevent bacteria and parasitism Insects and other complications. When the environment changes, the bait should be administered and the water body disinfected, such as Qiang 101. 2, gill disease (jaundice, black gills) Symptoms: gill filaments are gray or black, swollen, brittle, from the tip of the tip to the base of necrosis, ulceration. It usually occurs after heavy rain. The pathogen is Vibrio or other motility bacteria (such as Aeromonas bacillus) Control: 1 Summer and autumn high temperature season to raise the water level and maintain good water quality; 2 Less or no feeding of live food, absolutely prohibit the feeding of spoilage The small junk fish shrimp; 3 regularly (10 days or so) splash lime 5-10 kg / acre; 4 disease shrimp pond whole pool bromine chloride 0.3ppm, while feeding florfenicol (0.1%) or haloperidol Acid (0.05%) and other baits. 5-7 days for a course of treatment. 3, red leg disease symptoms: appendage become red, especially swimming feet become red, head thoracodorsal area yellow. Shrimp is generally slow in the shallow water or poolside, anorexia, haemolysis and slow coagulation or non-solidification. The pathogen is Vibrio parahaemolyticus or Vibrio anguillarum. Prevention: Ibid. 4. Symptoms of muscular white turbidity and rickets: The white muscles of the shrimp's abdominal muscles become opaque, and some of the body's muscles become white and turbid; some shrimps are sickle-like and both eyes are close together. The abdomen bends to the ventral side, and the severe part of the abdomen is below the head and chest, accompanied by muscle turbidity and death. Cause: Water temperature is too high, salinity is too high or too low, low dissolved oxygen, high density, etc. may be induced, shrimp may be induced by the disturbance. Control: Suitable for stocking density. Maintain high water level in high temperature season, do not make sharp changes in physical and chemical factors, and frequent human disturbances. 5, fixed ciliate symptoms: black area, appendages, eyes and body surface of the body are gray-black villous. Shrimp floats on the water. Outliers alone, unresponsive, loss of appetite to stop eating, can not molting; midnight to dawn, the shrimp pool dissolved oxygen below 3mg / l, often due to breathing difficulties. Etiology: Ciliate is a fixed type, common polyhydrazone, single dwarf, bell-shaped insects, slugs and sheath insects. In the middle and later stages of shrimp rearing, these ciliates have caused them to multiply and attach to shrimps due to the pool of water containing large amounts of organic debris, difficulty in changing shrimp ponds, or primary pathogenic organisms such as bacteria and viruses in shrimps. body. Prevention: 1 appropriate amount of water in the middle and late period of breeding, reasonable feeding, reduce the organic content of the shrimp pond; 2 oxygenation measures to maintain the pool water-soluble oxygen is not less than 5mg / l; 3 check the diagnosis of shrimp body with bacterial or viral infection If so, coping with disease prevention and control; 4 tea seed cake Quanchiposa, the concentration of 10-15ppm or tea saponin concentration of 1-2ppm, to promote shrimp molting, water change after molting; 5 zinc sulfate 0.8-1.0ppm Quanchiposa. X. Harvesting timely harvest is an important factor in the high yield and harvest of shrimp aquaculture. The time of harvest should be determined according to the market demand, the law of value and the growth of shrimp, health status, water temperature changes, water quality and sediment contamination, and bait resources. Under normal conditions, shrimp should be collected regularly, their average weight measured and their overall production checked. The proportion of softshell shrimp should not exceed 5% when collecting shrimp. Therefore, it is necessary to take measures to predict the shelling period of shrimps. There are a large number of shrimp shells in shrimp ponds, indicating that a large proportion of shrimps are in shells. Shrimp collection should be scheduled for half of the next shelling period (see attached table). For example, if the shrimp has an average body weight of 30 grams, then the shrimp should be harvested 7-8 days after the observation of the oyster shell. There are two ways to harvest shrimp: one is the drainage method, and the net is used to collect shrimp; the other is to use nets to catch shrimp in the shrimp pond. The drainage method is characterized by the use of prawn swimming along the pool and weaker currents, along with strong flow. Install gates on the outer slot of the drainage sluice. Use rapid release of water to harvest shrimp. This method has the advantages of good shrimp collection and labor saving. The shrimp collected is not contaminated by the bottom sludge of Akachi, and is suitable for large-scale harvesting of shrimp. In the pool, nets are used to catch shrimps, which use rotary nets or small power grids, large trawls, or throwing nets to catch shrimps. The bottom of the pond is crushed and the shrimps are contaminated. This method is suitable for one-time harvesting. Schedule: Average body weight (g) between individual shell size and shelling Shelling interval (days) 2-5 7-8 6-9 8-9 10-15 9-12 16-22 12-13 23-40 14 -16 50-70 (female) 18-21 50-70 (male) 23-30