Green shrimp is an economic shrimp that is widely distributed in China's freshwater waters, has a mixed diet, grows fast, and has strong fertility. In the past, it was mostly wild, and many areas now have artificial breeding. Cage culture shrimp has the characteristics of short breeding cycle, high survival rate, rapid efficiency, and good efficiency. It is a very promising breeding method and an important way to exploit and utilize large water resources. In recent years, the author has directed agricultural production to use rivers, lakes, reservoirs, and other large water surfaces, and used its advantages of fresh water and sufficient dissolved oxygen to carry out high-efficiency aquaculture of cages of shrimp and achieved good results. These are summarized as follows, with a view to Shrimp farming helps.
First, the selection of aquaculture waters The choice of open water, slow water flow, small waves, quiet environment, sunny, avoid the main channel, the water depth of 2m - 4m, flat bottom, less sludge surface. It requires fresh water and no pollution. The pH of the water body is 7.0--8.5, the dissolved oxygen is above 4.8mg/L, and the contents of nitrate nitrogen and nitrite nitrogen are not higher than 20ppm and 0.1ppm, respectively. In general, coves, lakes, rivers, wandering or larger ponds can be equipped with shrimp cages.
Second, cages and settings
1. Cage requirements. It is usually made of polyethylene mesh cloth, and the box is made of rectangles. Boxes are made of bamboo and used as open-floating or wood-pile fixed cages. There are three types of cages: large-, medium-, and small-sized. The size of a large cage is 40-60 square meters, the size of medium-sized cages is 20-300 square meters, and the size of small-sized cages is 1-square-- 10 square meters. In actual production, the area of ​​cages for shrimps is appropriate from 30m2 to 40m2, and the specifications are preferably 6mx4.5mx1.5m or 7mx3mx1.5m. In addition, the mesh of the bottom of the box and the wall is 20 mesh. Square cm - 30 mesh/cm2 is better.
2. The installation of cages. The cage is preferably installed as a floating type and can be freely raised and lowered as the water level changes. When installing, use bamboo roots and make a rectangular frame that matches the specifications of the cage. Make a round hole with a diameter of about 5 cm in each corner of the bamboo frame. Insert a length of 1.4-1.5 m into each hole. One bamboo tip, 0.9m--1.0m below the insertion hole; the lower end of the bamboo tip is fitted with a simple pulley, and the four corner tethers at the bottom of the box are respectively fixed on the bamboo frame through the pulley. The four corner tethers and the bamboo shoots of the anti-evacuation net are fastened at the upper end of the bamboo tip. A bamboo pole with a length of 1.4m--1.5m is tied every 2m around the net wall of the cage. The lower end of the bamboo strip is tied to the bottom rope of the box, and the upper end is tightly fastened with the anti-escape wire after being tightened. A pair of bamboo piles are placed in the four corners of the box. The bottom of the box is put into the mud, and the upper end is exposed to the water surface. Then the tip of the top of the bamboo fixed on the cage is tied with the bamboo pile with a rope, and the cage is submerged into the water at 0.9m-- 4.0m, mesh exposed 0.3m--0.4m to prevent escape. The cage layout is arranged in rows of 5 cages each with a box spacing of 4m to 5m and a row spacing of 5m to 6m.
3. Shrimp nest set. In order to improve the utilization of cage water for shrimp farming, shrimp cages should be set up in cages. After setting up fresh shrimps, stock 3 to 5 square meters of water hyacinth and duckweed, etc., in each box, and arrange them longitudinally by cages in accordance with the ropes, and do not stick to the wall to prevent the shrimps from becoming water grass. As a ladder climbed along the wall. The role of shrimp nests: First, to provide habitat for shrimp; Second, the roots of plants grow green root can be used as a green feed for shrimp; Third, the water can be used as a natural feed bait feed, and fourth, there are shade sun protection, dark Cooling effect; Fifth, after the winter, the plants are submerged by frost, which can be used as a winter warming place for the shrimp.
Third, the release of shrimp
1. Specifications and density. Cage-fed shrimp can be fed for 1 year if there are enough shrimps. The first batch is spring-breeded, usually wintering mid-March to raise wintering shrimp, stocking young prawns with a specification of 1000/kg-2000/kg, stocking density of about 400/m2; second batch at the end of July. Before and after the first batch of freshwater shrimps were caught in the summer and autumn, and the young prawn were stocked in the same year, the stocking specifications were generally 3000/kg--5,000/kg, and the stocking density was about 500/m2.
2. Restocking. The juvenile shrimps were immersed in cages for 4 days to 5 days before they were placed under the boxes, and the shrimps were started to be stocked with mud or algae. The larvae must be weighed, counted, and operated with water, and they should not be exposed to sunlight, otherwise they will affect the survival rate. During the operation, the juveniles cannot be stacked and the time of leaving the water cannot exceed 5 minutes. The juvenile shrimps in the same cage should have the same specifications and be allowed to leave at once. The time for leaving the boxes is usually selected in the morning and evening on a cloudy or sunny day. The operation should be careful and the movement should be light. Do not injures the shrimp. The transported juveniles are kept for a period of one day, and the dead shrimps and the injured shrimp bodies are removed before they are placed in the box.
Fourth, feeding and management
1. feed. Green prawns are omnivorous animals with a wide range of feed sources and should be adapted to local conditions. Feed can be used rice bran, wheat bran, soybean meal, peanut meal, snail, fish, fish meal, silkworm meal, etc. Rice bran and glutinous rice are recommended as the main feed for the shrimp in the rice production area, but with 20% - 25% Animal foods, such as fish, snails, clam meat, silkworm cocoons, cockroaches and so on.
2. Feed formulation. According to experience, feeds fed with freshwater shrimp are best formulated with pelleted feeds containing more than 30% protein, with a low feed rate and fast growth.
3. Feeding. Cage cultured green prawns are fed twice a day, and the daily feeding amount is generally 4%-6% of the shrimps in the crate. The specific feeding amount is increased or decreased depending on the feeding conditions of the crayfish and the weather changes. The weather is clear and the water temperature is It is appropriate to make more injections, and conversely, less should be used. Generally, feeds should be fed with fresh shrimp for 2 hours - food intake should be completed within 3 hours. When feeding specifically, one-third of the daily feed is fed in the morning and 2/3 of the daily feed is fed in the evening. Feeding the feed should be cast in the whole box, with the focus feeding in the water grass. In addition, due to the fact that the shrimp have the characteristics of holding food, swimming, feeding and discarding, the feed pellets should not be too large, and the general particle size should be 0.2cm--0.3cm.
4. Daily management. Mainly to do a good job of "four diligence" and "four defenses." The “four diligence†is: patrolling the ground, insisting on morning patrol inspections, testing water quality, observing the activities of shrimps and feeding conditions, removing residual baits, making daily inspections of the patrol ponds, and checking whether the nets of the cages are open and broken. Scrubbing nets to prevent adhesion of sediment, excessive algae and clogging the mesh, affect the exchange of water; ground maintenance, keep the box stable, the tether is strong, the box intact. The “four defenses†are: First, prevent flight; Second, prevent enemy damage. Since the water in the tank is small, once the wild fish and other predators are present, the shrimp will suffer heavy losses and should be checked frequently. Normally, it is cleared once every 15 days or so. The third is the sudden change of water quality and pesticide pollution: The fourth is to prevent caissons, burglary, theft and other hazards.
5. Fishing. Take measures to catch up on the market and stay small to continue farming. After one month of juvenile prawn rearing in spring, the fish can be picked and caught once every two months. Green prawn weighing more than 2.5g, ie, a size of 300 pigs/kg--400 pigs/kg, will be picked and listed. By the end of July, all tanks will be discharged. In the summer and autumn, juvenile larvae reared for breeding began to be arrested one month later, and they were arrested and stayed small until the end of November.
Fifth, shrimp disease prevention and control cage culture of shrimp, the prevention and treatment of diseases should implement the "prevention-based" approach. Because the water flow in the cage is fast, the water body is not easy to lack oxygen, and there are few enemy predators, so shrimp disease rarely occurs. Mollusca parasitic disease (black shank) and leukoplakia are two major diseases.
1. Mollusca parasitic disease. Molluscs parasitize in the crests, body surface, etc. of the shrimps. The prevention and control methods can be prevented by 1ppm bleaching powder dipping or bleaching powder (lime can also be used).
2. White spot disease. Also known as muscle necrosis, the white muscle in the abdominal muscles of diseased shrimp, and as the condition worsens, the white spot also grows small and large, and eventually spreads to the entire body and causes the shrimp to die. Both juvenile shrimp and adult shrimp can be infected. The disease is caused by a virus infection. It occurs when the water temperature changes widely, the water temperature is too high, and the water quality deteriorates. Therefore, the juvenile should pay attention to the temperature difference of the water body after entering the box. Keep fresh water in management and feed live bait to reduce the incidence of this disease. The prevention and control method is to put 2.5 g/m3 of oxytetracycline into the water body.
Intensive breeding of green shrimp breeding technology Green shrimp ponds, cages, rice field scale breeding and large surface proliferation, the need for a large number of high-quality shrimp, therefore, to adopt artificial control conditions under the breeding of shrimp species, in production is of great significance. Over the past few years, the author has conducted in-depth research on broodstock breeding, breeding, and seedling raising of young shrimps, simultaneously carried out demonstration and promotion of comparative scale, and achieved satisfactory results and economic benefits. The technology is summarized as follows.
I. Preparation for breeding ponds
1. Breed pond conditions. The area of ​​the breeding pond for shrimps is 0.2 hectares - 0.3 hectares, the depth is 1.0m - 1.2m, and the pond slope ratio is 2.5 - 3.0:1, set at the outlet Set shrimp pond 20 square meters - 30 square meters. Breeding ponds should be selected from areas with sufficient water, fresh water, no pollution, and convenient drainage and irrigation.
2. Breeding pond clearing. One month before breeding, shrimp ponds were trimmed, reconstructed, and exposed in dry ponds. During the first 15 days of feeding eggs and broodstock, the ponds were first filled with water about 10 cm, and the ponds were disinfected with quicklime at 200 kg/mu. Five days after clear ponds. - Start water in -7 days, the water level is about 80cm, and the water inlet and outlet are filtered with a double layer of 80 mesh - 100 mesh sieve to prevent wild fish, frog eggs and other predator organisms from entering the breeding pool.
Second, the food culture of food organisms The abundance of food organisms is the key factor in breeding the survival rate of young larvae. The rich food organisms provide the ideal open bait for the development of the larvae of the shrimp, and its nutritional value is more comprehensive than the artificial feed. And can reduce the pollution of the pond bottom, keep the water fresh, so, in the first 5 days - 7 days after the broodstock broodstock, breeding ponds should be applied after fermentation of organic fertilizer 300kg/mu - 500kg/mu.
Third, the selection and breeding of broodstock
1. The choice of broodstock. Green-crawling broodstock broodstock is generally caught in large water surfaces such as lakes, reservoirs, ditches, and ponds in mid-to late May. Select lively females with complete limbs, body lengths up to 5 cm, and mature or nearly mature female ovaries as broodstocks. Ovary volume covers almost the entire back, the front end reaches the base of the forehead, and the egg's color is green or orange (if The color of the egg is gray-brown and appears eye spots, indicating that the egg has hatched and is easily detached from the mother, which is inconvenient for transportation and operation). The amount of stock for broodstock brooding is 8kg/mu -10kg/mu.
2. The breeding of shrimp. Practice has proved that the cultivation of brooding broodstock and zoea larvae is better performed with a small area of ​​intensive cultivation. The specific operation method is to use a 0.5cm mesh, 1.2m high polyethylene mesh, mesh The bottom edge is buried in the mud and compacted, enclosing it in the corner of the pond, covering an area of ​​50 m2 - 60 m2. Water plants such as water hyacinths, water peanuts and other fresh aquatic plants are placed along the perimeter of the fence, occupying the fence. From 20% to 30% of the surface of the water, brooding broodstock is placed in a fence to be cultivated. After the broodstock is released, check the development of the shrimp eggs every day. After the juvenile larvae are all detached from the mother, use lobster cages and other fishing tools to remove the prawn from the market. At this time, press 150kg/mu--200kg/mu in the cultivation pond. Apply fermented organic fertilizer and continue to cultivate the bait's food organisms.
The wavy larvae in the seine nets are bred with cooked fish broth and egg yolks. The broth and egg yolks are sputtered after being filtered through 60 mesh-80 mesh sieves. Four times a day, 10,000 shrimp per 10,000 shrimps are fresh fish. And 2 egg yolks are fed. The larvae have been intensively cultivated for a week, and their body length has reached about 0.5cm. The segregation nets can be gently removed for seedling cultivation. The seedlings were changed to fish and egg yolk as soybean milk in the early stage of cultivation. Each day, 3 kg of soybeans were used to grind the soybean milk into 3 batches of feed. After 15 days of cultivation, the length of the shrimp seedlings was about 1 cm, except for the daily soymilk feed. Increase the feeding rate of feeds and feeds. The feed volume accounts for about 5% of the body weight of the shrimps. It is fed twice a day. The amount of feed in the morning accounts for 20% of the total amount of feed, and the amount of feed in the afternoon accounts for 80%, along the pool. The shallow water area is fed at multiple points.
IV. Water Quality Management Water quality management of shrimp breeding is mainly to ensure that there are abundant food organisms, adequate dissolved oxygen, and appropriate pH. It takes 35 days to 40 days for larvae to grow to 1.5cm--2.0cm in length. The stocking densities during seedling cultivation are large and the water quality is variable. Water quality, transparency and the eating and feeding of shrimps should be used to adjust the water quality in time. , strengthen the scientific management of water quality.
1. Timely and appropriate fertilization and water injection and drainage. While controlling the pond water body fatness, it is also necessary to meet the growth needs of shrimp feeding on natural food organisms. Under normal circumstances, the shrimp nursery ponds are fertilized 2 times - 3 times a month, and 150 kg of organic fertilizer is applied each time. 200kg, and timely drainage according to the transparency of the pool water. The water depth of the pond during the post-cultivation period of the penaeid shrimp needs to be added between 1.0m and 1.2m to ensure that the penaeid shrimp grows in a good environment.
2. Adjust the pH of the water body. Green shrimp live in a slightly alkaline water body. With the input of artificial diet and organic fertilizer, the pH of the water body slowly decreases. The pH of the water body should be tested once a week. If the pH value is 5, the shrimp seedlings will be harvested. As long as 1.5cm--2.0cm, the stocking density of seedlings in nursery ponds is already quite large. In order to increase the emergence rate per unit area, the ponds should be divided in time. The fishing tools of the shrimp seedlings can be gently pulled out by the fry nets. The light trapping can also be performed according to the characteristics of the clustered phototaxis of the shrimp seedlings, and a triangular handprinting net made from a 30 mesh to a 40 mesh sieve is repeatedly captured at the poolside.
Measures and Recommendations for Improving the Yield of Green Pond Cultured Prawn in Recent Years With the deepening of the research on the growth characteristics, nutritional requirements, and pellet feed of the shrimp, the shrimp culture has developed into a “low input, high output†high efficiency breeding model. , And achieved a good demonstration of the promotion effect. Due to the late start of aquaculture in Anhui Province and the Jiangsu, Zhejiang and other places, the technology is not mature enough and the yield is low, which seriously affects the farmers' benefits. Therefore, how to effectively increase the yield has become an urgent task.
First, the cause of the low yield of fresh shrimp
1. Aquaculture ponds are not standardized. First, poor pond water quality, single pond area is unreasonable, pool water depth is too shallow or too deep, and second, pond silt is thick, slope ratio is small, clear pond is not complete, and enemies are many; third, inflow and outflow are not strictly filtered, and no attachment is provided. Objects or transplanting aquatic plants.
2. Improper timing, size, and density of seedlings, often results in the formation of “several generations of fellows†in the pond, with small commodity sizes and low market rates.
3. Feeding management technology can not keep up. The first is water quality management. Since water quality controls the degree of water body fat and dissolved oxygen, it can be adapted to the growth needs of the shrimp. However, in most farmers, only knowing that cultivating freshwater requires high dissolved oxygen in the water and neglecting water quality. "Fat, live, cool" three elements; Second, feed selection and application is irrational, in the breeding of rice bran, cabbage and other mixed mushy feeding, there is no match with animal feed, feed utilization is low, and easy to deteriorate water quality.
Second, measures to increase the yield
1. Renovate pond conditions
(1) The area, shape and depth of the pond are generally 3 mu - 5 mu. The rectangle is appropriate. The depth of the pond is required to be about 1.2m. If the water level is too shallow, the temperature difference between day and night will change greatly. If the water depth is too deep, the vertical dissolved oxygen in the water will differ. Large, not conducive to the growth of shrimp.
(2) Pond clearing. To remove excess silt, the sediment is kept at about 10cm, and the slope of the pond is trimmed at 1:2.5-1:3 so that the shrimp can feed at night. If it is a old pond, it is best to bring clear ponds to kill predators such as yellow locusts and loach.
(3) Transplant aquatic plants. If there is no aquatic grass in the breeding pond, aquatic plants such as water peanuts and Vallisneria can be transplanted. The transplanted area accounts for about 30% of the pond area, and the transplanted location is generally 2.0m long from the pond and is in a long strip shape. Aquatic plants can both purify water and avoid hostilities. Green feed can also be provided.
2. Adjust water quality and increase dissolved oxygen in water
(1) Apply fertilizer timely. It is the key to grasping both the "fat" and "living" water quality, specifically "fat two heads, clear middle". "Fat two-headed" refers to the stage from shrimp seedlings to juveniles and late autumn. "Clearing the middle" refers to the high-temperature period of August-September, requiring fresh water to prevent oxygen deprivation. Fertilizer can be used as compound fertilizer with dosage of 5kg/mu -10kg/mu.
(2) timely water injection. Less water is added during the initial period of cultivation and during the latter period of cultivation. Water is added during the middle period of cultivation. Adding fresh water can increase the dissolved oxygen, nutrients and trace elements in the water, increase the appetite of the shrimp, and reduce the concentration of metabolic poisons and prevent pool water from aging. When water is added, the water should be filtered to prevent the enemy from entering the pond with the water.
(3) timely adjust the pH of the water body. The lime is splashed twice a month and the pH of the pool water is maintained between 7.0 and 8.0 to facilitate the growth of the shrimp clams.
3. Improve stocking mode and adjust stocking density
(1) Improve stocking mode and adjust "family generations". Due to the rapid growth of shrimp, the majority of fish farmers rely mainly on stocking and holding eggs, adopting self-cultivation, self-breeding, and self-support. This farming method is extensive farming. Although it is convenient and practical, it is difficult to control the breeding density and it is easy to produce “several generations of the same. "Tang", the market size of fresh shrimp is not uniform, and the yield is not high. Therefore, to increase the yield and efficiency of shrimp production, it is necessary to adopt extensive farming as the intensive cultivation, change the stocking and holding of the shrimp to stocking the shrimp, and change the amount of shrimp to two. Shrimp and other technical measures.
(2) Adjust the stocking density and increase the listing size. The high stocking density of shrimps not only results in the killing of shrimps when there is insufficient feed, but also results in low yields and small commodity sizes; the stocking density is too low and the water use efficiency is low. The stocking density should be 40,000/mu - 50,000/mu.
4. Feed structure adjustment, scientific feeding of freshwater prawn as omnivorous animals, breeding of two freshwater prawn in one year has two peak feeding periods, namely April-May and August-October, June-July For the growth of young shrimp during the breeding season, the food intake will decline and the above characteristics will be grasped to facilitate scientific feeding.
(1) Select pellet feed. At present, a variety of commercial feeds can be used to feed fresh shrimp. However, fresh shrimps have different levels of feed and utilization for various commercial feeds. The animal feeds that the shrimps like to eat include snails, fish meal, and fish gills, and the feeds for the crops include bean cakes, rice bran, bran, and the like. Most farmers use the mixed mash feed such as vegetable cakes and rice bran, which has low utilization rate and is likely to deteriorate water quality. Therefore, green prawn intensive, the best use of pellet feed, and animal feed more than 30% is appropriate.
(2) Reasonable feeding. Green shrimp like to feed along the pool at night, and can observe the feeding conditions of the shrimp. Generally, they are fed twice a day. The amount of feed in the morning accounts for 30% of the total feeding amount in the day and 70% in the evening.
5. The timely removal of wild fish After a period of cultivation, a small amount of wild fish may appear in the pond. If it is not cleared in time, the wild fish competes with fresh shrimp and consumes dissolved oxygen in the water.
Third, the proposal
1. The best choice for the green shrimp seedlings is in the large-scale waters with the size of 150/kg--200 tails/kg. The broodstock with the same degree of shrimp development is screened, and hatching and nursery are centralized to make the shrimps of the same size.
2. With the deployment of fresh shrimp, one pond must be thrown in one-off quantities, which cannot be supplemented and supplemented, resulting in irregular seed specifications and the risk of unfavorable growth of shrimps such as killing each other.
3. Some hidden objects must be set in the pond. It is best to plant plants in the bottom of the pond. The plants are parallel to the pool and set into strip shapes. Each strip has a width of 1.0m. The total area of ​​the pond is about 30% of the pond area. .
4. Strictly prevent the occurrence of "Sweet Green Shatha" in shrimp ponds. The following two methods can be used to remove the shrimp ponds. First, the bamboo rafts are used manually to reach the downwind position, and the water is discharged from the outlet of the drain. The second is to dilute with copper sulfate. The sprayer is sprayed gradually and the drug concentration must not exceed 0.5 ppm.
First, the selection of aquaculture waters The choice of open water, slow water flow, small waves, quiet environment, sunny, avoid the main channel, the water depth of 2m - 4m, flat bottom, less sludge surface. It requires fresh water and no pollution. The pH of the water body is 7.0--8.5, the dissolved oxygen is above 4.8mg/L, and the contents of nitrate nitrogen and nitrite nitrogen are not higher than 20ppm and 0.1ppm, respectively. In general, coves, lakes, rivers, wandering or larger ponds can be equipped with shrimp cages.
Second, cages and settings
1. Cage requirements. It is usually made of polyethylene mesh cloth, and the box is made of rectangles. Boxes are made of bamboo and used as open-floating or wood-pile fixed cages. There are three types of cages: large-, medium-, and small-sized. The size of a large cage is 40-60 square meters, the size of medium-sized cages is 20-300 square meters, and the size of small-sized cages is 1-square-- 10 square meters. In actual production, the area of ​​cages for shrimps is appropriate from 30m2 to 40m2, and the specifications are preferably 6mx4.5mx1.5m or 7mx3mx1.5m. In addition, the mesh of the bottom of the box and the wall is 20 mesh. Square cm - 30 mesh/cm2 is better.
2. The installation of cages. The cage is preferably installed as a floating type and can be freely raised and lowered as the water level changes. When installing, use bamboo roots and make a rectangular frame that matches the specifications of the cage. Make a round hole with a diameter of about 5 cm in each corner of the bamboo frame. Insert a length of 1.4-1.5 m into each hole. One bamboo tip, 0.9m--1.0m below the insertion hole; the lower end of the bamboo tip is fitted with a simple pulley, and the four corner tethers at the bottom of the box are respectively fixed on the bamboo frame through the pulley. The four corner tethers and the bamboo shoots of the anti-evacuation net are fastened at the upper end of the bamboo tip. A bamboo pole with a length of 1.4m--1.5m is tied every 2m around the net wall of the cage. The lower end of the bamboo strip is tied to the bottom rope of the box, and the upper end is tightly fastened with the anti-escape wire after being tightened. A pair of bamboo piles are placed in the four corners of the box. The bottom of the box is put into the mud, and the upper end is exposed to the water surface. Then the tip of the top of the bamboo fixed on the cage is tied with the bamboo pile with a rope, and the cage is submerged into the water at 0.9m-- 4.0m, mesh exposed 0.3m--0.4m to prevent escape. The cage layout is arranged in rows of 5 cages each with a box spacing of 4m to 5m and a row spacing of 5m to 6m.
3. Shrimp nest set. In order to improve the utilization of cage water for shrimp farming, shrimp cages should be set up in cages. After setting up fresh shrimps, stock 3 to 5 square meters of water hyacinth and duckweed, etc., in each box, and arrange them longitudinally by cages in accordance with the ropes, and do not stick to the wall to prevent the shrimps from becoming water grass. As a ladder climbed along the wall. The role of shrimp nests: First, to provide habitat for shrimp; Second, the roots of plants grow green root can be used as a green feed for shrimp; Third, the water can be used as a natural feed bait feed, and fourth, there are shade sun protection, dark Cooling effect; Fifth, after the winter, the plants are submerged by frost, which can be used as a winter warming place for the shrimp.
Third, the release of shrimp
1. Specifications and density. Cage-fed shrimp can be fed for 1 year if there are enough shrimps. The first batch is spring-breeded, usually wintering mid-March to raise wintering shrimp, stocking young prawns with a specification of 1000/kg-2000/kg, stocking density of about 400/m2; second batch at the end of July. Before and after the first batch of freshwater shrimps were caught in the summer and autumn, and the young prawn were stocked in the same year, the stocking specifications were generally 3000/kg--5,000/kg, and the stocking density was about 500/m2.
2. Restocking. The juvenile shrimps were immersed in cages for 4 days to 5 days before they were placed under the boxes, and the shrimps were started to be stocked with mud or algae. The larvae must be weighed, counted, and operated with water, and they should not be exposed to sunlight, otherwise they will affect the survival rate. During the operation, the juveniles cannot be stacked and the time of leaving the water cannot exceed 5 minutes. The juvenile shrimps in the same cage should have the same specifications and be allowed to leave at once. The time for leaving the boxes is usually selected in the morning and evening on a cloudy or sunny day. The operation should be careful and the movement should be light. Do not injures the shrimp. The transported juveniles are kept for a period of one day, and the dead shrimps and the injured shrimp bodies are removed before they are placed in the box.
Fourth, feeding and management
1. feed. Green prawns are omnivorous animals with a wide range of feed sources and should be adapted to local conditions. Feed can be used rice bran, wheat bran, soybean meal, peanut meal, snail, fish, fish meal, silkworm meal, etc. Rice bran and glutinous rice are recommended as the main feed for the shrimp in the rice production area, but with 20% - 25% Animal foods, such as fish, snails, clam meat, silkworm cocoons, cockroaches and so on.
2. Feed formulation. According to experience, feeds fed with freshwater shrimp are best formulated with pelleted feeds containing more than 30% protein, with a low feed rate and fast growth.
3. Feeding. Cage cultured green prawns are fed twice a day, and the daily feeding amount is generally 4%-6% of the shrimps in the crate. The specific feeding amount is increased or decreased depending on the feeding conditions of the crayfish and the weather changes. The weather is clear and the water temperature is It is appropriate to make more injections, and conversely, less should be used. Generally, feeds should be fed with fresh shrimp for 2 hours - food intake should be completed within 3 hours. When feeding specifically, one-third of the daily feed is fed in the morning and 2/3 of the daily feed is fed in the evening. Feeding the feed should be cast in the whole box, with the focus feeding in the water grass. In addition, due to the fact that the shrimp have the characteristics of holding food, swimming, feeding and discarding, the feed pellets should not be too large, and the general particle size should be 0.2cm--0.3cm.
4. Daily management. Mainly to do a good job of "four diligence" and "four defenses." The “four diligence†is: patrolling the ground, insisting on morning patrol inspections, testing water quality, observing the activities of shrimps and feeding conditions, removing residual baits, making daily inspections of the patrol ponds, and checking whether the nets of the cages are open and broken. Scrubbing nets to prevent adhesion of sediment, excessive algae and clogging the mesh, affect the exchange of water; ground maintenance, keep the box stable, the tether is strong, the box intact. The “four defenses†are: First, prevent flight; Second, prevent enemy damage. Since the water in the tank is small, once the wild fish and other predators are present, the shrimp will suffer heavy losses and should be checked frequently. Normally, it is cleared once every 15 days or so. The third is the sudden change of water quality and pesticide pollution: The fourth is to prevent caissons, burglary, theft and other hazards.
5. Fishing. Take measures to catch up on the market and stay small to continue farming. After one month of juvenile prawn rearing in spring, the fish can be picked and caught once every two months. Green prawn weighing more than 2.5g, ie, a size of 300 pigs/kg--400 pigs/kg, will be picked and listed. By the end of July, all tanks will be discharged. In the summer and autumn, juvenile larvae reared for breeding began to be arrested one month later, and they were arrested and stayed small until the end of November.
Fifth, shrimp disease prevention and control cage culture of shrimp, the prevention and treatment of diseases should implement the "prevention-based" approach. Because the water flow in the cage is fast, the water body is not easy to lack oxygen, and there are few enemy predators, so shrimp disease rarely occurs. Mollusca parasitic disease (black shank) and leukoplakia are two major diseases.
1. Mollusca parasitic disease. Molluscs parasitize in the crests, body surface, etc. of the shrimps. The prevention and control methods can be prevented by 1ppm bleaching powder dipping or bleaching powder (lime can also be used).
2. White spot disease. Also known as muscle necrosis, the white muscle in the abdominal muscles of diseased shrimp, and as the condition worsens, the white spot also grows small and large, and eventually spreads to the entire body and causes the shrimp to die. Both juvenile shrimp and adult shrimp can be infected. The disease is caused by a virus infection. It occurs when the water temperature changes widely, the water temperature is too high, and the water quality deteriorates. Therefore, the juvenile should pay attention to the temperature difference of the water body after entering the box. Keep fresh water in management and feed live bait to reduce the incidence of this disease. The prevention and control method is to put 2.5 g/m3 of oxytetracycline into the water body.
Intensive breeding of green shrimp breeding technology Green shrimp ponds, cages, rice field scale breeding and large surface proliferation, the need for a large number of high-quality shrimp, therefore, to adopt artificial control conditions under the breeding of shrimp species, in production is of great significance. Over the past few years, the author has conducted in-depth research on broodstock breeding, breeding, and seedling raising of young shrimps, simultaneously carried out demonstration and promotion of comparative scale, and achieved satisfactory results and economic benefits. The technology is summarized as follows.
I. Preparation for breeding ponds
1. Breed pond conditions. The area of ​​the breeding pond for shrimps is 0.2 hectares - 0.3 hectares, the depth is 1.0m - 1.2m, and the pond slope ratio is 2.5 - 3.0:1, set at the outlet Set shrimp pond 20 square meters - 30 square meters. Breeding ponds should be selected from areas with sufficient water, fresh water, no pollution, and convenient drainage and irrigation.
2. Breeding pond clearing. One month before breeding, shrimp ponds were trimmed, reconstructed, and exposed in dry ponds. During the first 15 days of feeding eggs and broodstock, the ponds were first filled with water about 10 cm, and the ponds were disinfected with quicklime at 200 kg/mu. Five days after clear ponds. - Start water in -7 days, the water level is about 80cm, and the water inlet and outlet are filtered with a double layer of 80 mesh - 100 mesh sieve to prevent wild fish, frog eggs and other predator organisms from entering the breeding pool.
Second, the food culture of food organisms The abundance of food organisms is the key factor in breeding the survival rate of young larvae. The rich food organisms provide the ideal open bait for the development of the larvae of the shrimp, and its nutritional value is more comprehensive than the artificial feed. And can reduce the pollution of the pond bottom, keep the water fresh, so, in the first 5 days - 7 days after the broodstock broodstock, breeding ponds should be applied after fermentation of organic fertilizer 300kg/mu - 500kg/mu.
Third, the selection and breeding of broodstock
1. The choice of broodstock. Green-crawling broodstock broodstock is generally caught in large water surfaces such as lakes, reservoirs, ditches, and ponds in mid-to late May. Select lively females with complete limbs, body lengths up to 5 cm, and mature or nearly mature female ovaries as broodstocks. Ovary volume covers almost the entire back, the front end reaches the base of the forehead, and the egg's color is green or orange (if The color of the egg is gray-brown and appears eye spots, indicating that the egg has hatched and is easily detached from the mother, which is inconvenient for transportation and operation). The amount of stock for broodstock brooding is 8kg/mu -10kg/mu.
2. The breeding of shrimp. Practice has proved that the cultivation of brooding broodstock and zoea larvae is better performed with a small area of ​​intensive cultivation. The specific operation method is to use a 0.5cm mesh, 1.2m high polyethylene mesh, mesh The bottom edge is buried in the mud and compacted, enclosing it in the corner of the pond, covering an area of ​​50 m2 - 60 m2. Water plants such as water hyacinths, water peanuts and other fresh aquatic plants are placed along the perimeter of the fence, occupying the fence. From 20% to 30% of the surface of the water, brooding broodstock is placed in a fence to be cultivated. After the broodstock is released, check the development of the shrimp eggs every day. After the juvenile larvae are all detached from the mother, use lobster cages and other fishing tools to remove the prawn from the market. At this time, press 150kg/mu--200kg/mu in the cultivation pond. Apply fermented organic fertilizer and continue to cultivate the bait's food organisms.
The wavy larvae in the seine nets are bred with cooked fish broth and egg yolks. The broth and egg yolks are sputtered after being filtered through 60 mesh-80 mesh sieves. Four times a day, 10,000 shrimp per 10,000 shrimps are fresh fish. And 2 egg yolks are fed. The larvae have been intensively cultivated for a week, and their body length has reached about 0.5cm. The segregation nets can be gently removed for seedling cultivation. The seedlings were changed to fish and egg yolk as soybean milk in the early stage of cultivation. Each day, 3 kg of soybeans were used to grind the soybean milk into 3 batches of feed. After 15 days of cultivation, the length of the shrimp seedlings was about 1 cm, except for the daily soymilk feed. Increase the feeding rate of feeds and feeds. The feed volume accounts for about 5% of the body weight of the shrimps. It is fed twice a day. The amount of feed in the morning accounts for 20% of the total amount of feed, and the amount of feed in the afternoon accounts for 80%, along the pool. The shallow water area is fed at multiple points.
IV. Water Quality Management Water quality management of shrimp breeding is mainly to ensure that there are abundant food organisms, adequate dissolved oxygen, and appropriate pH. It takes 35 days to 40 days for larvae to grow to 1.5cm--2.0cm in length. The stocking densities during seedling cultivation are large and the water quality is variable. Water quality, transparency and the eating and feeding of shrimps should be used to adjust the water quality in time. , strengthen the scientific management of water quality.
1. Timely and appropriate fertilization and water injection and drainage. While controlling the pond water body fatness, it is also necessary to meet the growth needs of shrimp feeding on natural food organisms. Under normal circumstances, the shrimp nursery ponds are fertilized 2 times - 3 times a month, and 150 kg of organic fertilizer is applied each time. 200kg, and timely drainage according to the transparency of the pool water. The water depth of the pond during the post-cultivation period of the penaeid shrimp needs to be added between 1.0m and 1.2m to ensure that the penaeid shrimp grows in a good environment.
2. Adjust the pH of the water body. Green shrimp live in a slightly alkaline water body. With the input of artificial diet and organic fertilizer, the pH of the water body slowly decreases. The pH of the water body should be tested once a week. If the pH value is 5, the shrimp seedlings will be harvested. As long as 1.5cm--2.0cm, the stocking density of seedlings in nursery ponds is already quite large. In order to increase the emergence rate per unit area, the ponds should be divided in time. The fishing tools of the shrimp seedlings can be gently pulled out by the fry nets. The light trapping can also be performed according to the characteristics of the clustered phototaxis of the shrimp seedlings, and a triangular handprinting net made from a 30 mesh to a 40 mesh sieve is repeatedly captured at the poolside.
Measures and Recommendations for Improving the Yield of Green Pond Cultured Prawn in Recent Years With the deepening of the research on the growth characteristics, nutritional requirements, and pellet feed of the shrimp, the shrimp culture has developed into a “low input, high output†high efficiency breeding model. , And achieved a good demonstration of the promotion effect. Due to the late start of aquaculture in Anhui Province and the Jiangsu, Zhejiang and other places, the technology is not mature enough and the yield is low, which seriously affects the farmers' benefits. Therefore, how to effectively increase the yield has become an urgent task.
First, the cause of the low yield of fresh shrimp
1. Aquaculture ponds are not standardized. First, poor pond water quality, single pond area is unreasonable, pool water depth is too shallow or too deep, and second, pond silt is thick, slope ratio is small, clear pond is not complete, and enemies are many; third, inflow and outflow are not strictly filtered, and no attachment is provided. Objects or transplanting aquatic plants.
2. Improper timing, size, and density of seedlings, often results in the formation of “several generations of fellows†in the pond, with small commodity sizes and low market rates.
3. Feeding management technology can not keep up. The first is water quality management. Since water quality controls the degree of water body fat and dissolved oxygen, it can be adapted to the growth needs of the shrimp. However, in most farmers, only knowing that cultivating freshwater requires high dissolved oxygen in the water and neglecting water quality. "Fat, live, cool" three elements; Second, feed selection and application is irrational, in the breeding of rice bran, cabbage and other mixed mushy feeding, there is no match with animal feed, feed utilization is low, and easy to deteriorate water quality.
Second, measures to increase the yield
1. Renovate pond conditions
(1) The area, shape and depth of the pond are generally 3 mu - 5 mu. The rectangle is appropriate. The depth of the pond is required to be about 1.2m. If the water level is too shallow, the temperature difference between day and night will change greatly. If the water depth is too deep, the vertical dissolved oxygen in the water will differ. Large, not conducive to the growth of shrimp.
(2) Pond clearing. To remove excess silt, the sediment is kept at about 10cm, and the slope of the pond is trimmed at 1:2.5-1:3 so that the shrimp can feed at night. If it is a old pond, it is best to bring clear ponds to kill predators such as yellow locusts and loach.
(3) Transplant aquatic plants. If there is no aquatic grass in the breeding pond, aquatic plants such as water peanuts and Vallisneria can be transplanted. The transplanted area accounts for about 30% of the pond area, and the transplanted location is generally 2.0m long from the pond and is in a long strip shape. Aquatic plants can both purify water and avoid hostilities. Green feed can also be provided.
2. Adjust water quality and increase dissolved oxygen in water
(1) Apply fertilizer timely. It is the key to grasping both the "fat" and "living" water quality, specifically "fat two heads, clear middle". "Fat two-headed" refers to the stage from shrimp seedlings to juveniles and late autumn. "Clearing the middle" refers to the high-temperature period of August-September, requiring fresh water to prevent oxygen deprivation. Fertilizer can be used as compound fertilizer with dosage of 5kg/mu -10kg/mu.
(2) timely water injection. Less water is added during the initial period of cultivation and during the latter period of cultivation. Water is added during the middle period of cultivation. Adding fresh water can increase the dissolved oxygen, nutrients and trace elements in the water, increase the appetite of the shrimp, and reduce the concentration of metabolic poisons and prevent pool water from aging. When water is added, the water should be filtered to prevent the enemy from entering the pond with the water.
(3) timely adjust the pH of the water body. The lime is splashed twice a month and the pH of the pool water is maintained between 7.0 and 8.0 to facilitate the growth of the shrimp clams.
3. Improve stocking mode and adjust stocking density
(1) Improve stocking mode and adjust "family generations". Due to the rapid growth of shrimp, the majority of fish farmers rely mainly on stocking and holding eggs, adopting self-cultivation, self-breeding, and self-support. This farming method is extensive farming. Although it is convenient and practical, it is difficult to control the breeding density and it is easy to produce “several generations of the same. "Tang", the market size of fresh shrimp is not uniform, and the yield is not high. Therefore, to increase the yield and efficiency of shrimp production, it is necessary to adopt extensive farming as the intensive cultivation, change the stocking and holding of the shrimp to stocking the shrimp, and change the amount of shrimp to two. Shrimp and other technical measures.
(2) Adjust the stocking density and increase the listing size. The high stocking density of shrimps not only results in the killing of shrimps when there is insufficient feed, but also results in low yields and small commodity sizes; the stocking density is too low and the water use efficiency is low. The stocking density should be 40,000/mu - 50,000/mu.
4. Feed structure adjustment, scientific feeding of freshwater prawn as omnivorous animals, breeding of two freshwater prawn in one year has two peak feeding periods, namely April-May and August-October, June-July For the growth of young shrimp during the breeding season, the food intake will decline and the above characteristics will be grasped to facilitate scientific feeding.
(1) Select pellet feed. At present, a variety of commercial feeds can be used to feed fresh shrimp. However, fresh shrimps have different levels of feed and utilization for various commercial feeds. The animal feeds that the shrimps like to eat include snails, fish meal, and fish gills, and the feeds for the crops include bean cakes, rice bran, bran, and the like. Most farmers use the mixed mash feed such as vegetable cakes and rice bran, which has low utilization rate and is likely to deteriorate water quality. Therefore, green prawn intensive, the best use of pellet feed, and animal feed more than 30% is appropriate.
(2) Reasonable feeding. Green shrimp like to feed along the pool at night, and can observe the feeding conditions of the shrimp. Generally, they are fed twice a day. The amount of feed in the morning accounts for 30% of the total feeding amount in the day and 70% in the evening.
5. The timely removal of wild fish After a period of cultivation, a small amount of wild fish may appear in the pond. If it is not cleared in time, the wild fish competes with fresh shrimp and consumes dissolved oxygen in the water.
Third, the proposal
1. The best choice for the green shrimp seedlings is in the large-scale waters with the size of 150/kg--200 tails/kg. The broodstock with the same degree of shrimp development is screened, and hatching and nursery are centralized to make the shrimps of the same size.
2. With the deployment of fresh shrimp, one pond must be thrown in one-off quantities, which cannot be supplemented and supplemented, resulting in irregular seed specifications and the risk of unfavorable growth of shrimps such as killing each other.
3. Some hidden objects must be set in the pond. It is best to plant plants in the bottom of the pond. The plants are parallel to the pool and set into strip shapes. Each strip has a width of 1.0m. The total area of ​​the pond is about 30% of the pond area. .
4. Strictly prevent the occurrence of "Sweet Green Shatha" in shrimp ponds. The following two methods can be used to remove the shrimp ponds. First, the bamboo rafts are used manually to reach the downwind position, and the water is discharged from the outlet of the drain. The second is to dilute with copper sulfate. The sprayer is sprayed gradually and the drug concentration must not exceed 0.5 ppm.
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