Crab seedlings, also known as big eye larvae, usually have 141-160,000 birds per kilogram, and only weigh 6-7 milligrams. Their ability to find bait and avoid predators is poor. If directly put into large lakes such as lakes, crab pools, etc., the survival rate must be very low, which is also a great waste of crab seedling resources. Therefore, whether it is natural crabs or artificially propagated crabs, it should generally be cultivated for 20-40 days to allow the crabs to peel 3-5 times and develop into 3- to 5-phase crabs to enhance the environment. adaptability. If you continue to grow a few grams of young crabs, and then put more water to develop crabs, more adaptable, the survival rate will be even higher.
The quality of crab seedlings directly affects the results of larval rearing. It is also one of the keys to the success or failure of adult crab breeding. Therefore, we must choose natural crabs in the Yangtze River Estuary or crabs artificially propagated in the Yangtze River water system. In the specific selection of crab, you can pay attention to the following aspects:
The first is to see the color. High-quality crab seedlings are generally light yellow or gray-gray, with bright color;
The second is to look at vitality. High-quality crab seedlings are full of vitality, quickly spread by hand after being loosened, and quickly swam around in water;
The third is to see the specifications. High-quality crab seedlings have the same specifications and uniform size, generally no more than 160,000 per kilogram;
The fourth is to look at impurities. High-quality crab seedlings should contain no impurities and no dead seedlings;
The fifth is to look down on the time. In artificially propagated crab seedlings, more than 80% of the juveniles grow into large ocular larvae and begin to fade. The dilution time is generally not less than 100 hours.
Here are some ways to cultivate young and young crabs.
First, cages to cultivate crabs
1, the production of cages: nets can be used polyethylene mesh or nylon sieve, length, width, height were 2,1,1 meters, or 4,2,1 meters, or 4,3,1 meters, net Head 0.8-1 mm. The cage is supported with bamboo, etc., to open the box. The cage should be covered, and a door that can be opened and closed at the junction between the cover and the side of the box should be closed. The zipper should be sewn and closed normally.
2, cage settings: cages should be located in non-polluting lakes, reservoirs, rivers, or deeper ponds, preferably with micro-flowing water, in order to maintain a high level of dissolved oxygen. About 20 cm of the box is exposed above the water, 80 cm sinks into the water, and the box is 3 to 5 meters away. Water hyacinths, water lettuces, water peanuts and other plants should be placed inside the box, which generally accounts for about one-half of the area inside the box, or about 1 kilogram of fresh grass per square meter, making it easy for the crabs to attach and inhabit.
3, crab seedlings: different areas, different stocking densities at different times, the density of 0-2 million per square meter, ranging from about 10,000 per square meter.
4. Feeding: The basic requirement is that the bait nutrition should be rich and fresh, and the particle size must be in the middle, and the quantity of the feed should be sufficient. Optional soy milk, egg yolk, can also be used to process finely broken snails, quail meat, or granular feed crushing feed, you can also fish out zooplankton (red worms), leeches and other feeding. Feeding 3 to 4 times a day, the daily feeding amount can account for about 50% of the body weight of the crabs. With the continuous growth of the crabs, the latter can account for 10% to 15% of the body weight. The bait should be sprinkled on the stems and leaves of water plants and be distributed evenly.
5, daily management: To check whether the cage is damaged, to prevent fleeing seedlings. Regularly wash the net to prevent it from clogging the mesh and make the exchange of water inside and outside the box unsmooth. To prevent water mice, water snakes, etc. into the box to harm crabs. After 20-40 days of cultivation, crab seedlings develop into 3-5-phase juvenile crabs. Harvest them in time and transfer them to earthen ponds to raise juvenile crabs in order to avoid disparities in the size of the boxes and the occurrence of similar disability and affect the survival rate.
Second, the cement pool to raise crabs
1. Cement pool conditions: The area is generally more than 10 square meters, less than 100 square meters, the depth of the pool is about 1 meter, and the pool-shaped square can be round. Water quality should be fresh and water should be sufficient. The pool should have inlets and outlets and be blocked with mesh cloth to avoid fleeing seedlings. At the bottom of the pool, you can put some broken bricks and tiles, and then put in water plants to make it easier for crabs to inhabit. The upper part of the pool wall should be smooth, and the pool should be covered with plastic film to prevent escape.
2, cement pool disinfection and fertilization: The new cement pool should be soaked with water for several days, and repeatedly change the water before the release of crab seedlings, the old pool before putting the seedlings to wash with 100ppm bleach solution again, 5-7 days after the water injection 40--50 cm, appropriate amount of fertilizer, pre-incubation of plankton, to prepare a good ecological environment and bait foundation for crab seedlings.
3, crab seedlings: cement ponds with normal conditions, 5000-6000 can be placed per square meter, better conditions, can often change the water or cement pool can keep micro-water, crabs per square meter can be put 10,000 about.
4. Feeding and management: Although crab seedlings cultivated plankton before fertilization, they could not meet the needs of growth and development of crabs, but also fed certain nutrient-rich baits. Every day can be divided into 2 - 3 times splash soy milk, soy flour, fish meal and other bait, the daily feeding amount is about 20% - 30% of the weight of crabs. Pay attention to spread evenly and cast more on the leaves of aquatic plants. The water is shallow at the beginning. In order to maintain rich dissolved oxygen and good water quality, it is often necessary to add water or change water. In the later stages of cultivation, the depth of pool water can gradually be added to 70-80 cm.
Third, the earth pond nurtures crabs
1, soil conditions: the area should not be too large, a few hundred square meters to thousands of square meters is better, the pool depth of about 1 meter, can maintain a depth of 70 - 80 cm. Long shape is better. The bottom of the pool is required to be flat, with less silt, no water leakage, solid pool floor, adequate water supply, good water quality, and easy access to water.
2, earthen pond disinfection: 15-20 days before the release of crab seedlings, drain the pool water, first make the bottom of the pool, then the orange juice (7)?铩I 矣昧 矣昧 旱 旱 旱 旱 旱 旱 旱 旱 . .. 5 meters, 60-80 kilograms per 667 square meters. With bleach, the pool water concentration is 20 ppm. The drug should be fully stirred and evenly spilled.
3, fertilization: Crab seedlings 5-7 days before the next tank, fertilizer should be applied to cultivate food organisms so that the crabs after the pond is a palatable natural food. Generally, 150-200 kilograms of fermented cow dung, pig dung, human waste, etc. can be applied per 667 square meters.
4, the release of crabs: crab seeding density, according to soil conditions, feeding conditions, out of the pool specifications and management level and other factors to determine, the current general every 667 square meters of crab seedlings 1.5-2 kg, good conditions can be Put 2-3 kg.
Due to the large area of ​​the earthen pond, it is difficult to evenly feed the fish. The crabs in the later period are often of great disparity. Therefore, the same batch of crabs should be placed in each pond, and the specifications must be the same.
5. Feeding and management: Crab seedlings and water ponds can use some natural foods, but it is difficult to meet the needs of the whole growing season. Pre-feeding can be mainly soybean milk, egg yolk, and fish gizzards. After one week, feed varieties can be expanded to bean cakes, wheat bran, small fish, shrimp, snail meat, and quail, etc. The feeds are ground and added into a paste. Sprinkle evenly in the early stage, and feed it along the earth pond at a certain point. Put the feed on shallow water or aquatic plants and other attachments. The amount of daily feeding can be controlled by 10% - 15% of the total weight of larvae, and it can be adjusted to about 10% in the later period. Every day from 7 to 8 in the morning and from 6 to 7 in the evening, the feeding is once in the evening, and the feeding amount can be 60% to 70%. The specific amount of feed per day depends on the food intake and weather conditions of the crabs.
When the crabs are in the pool, the pool water can be kept at about 50 cm. The pool water is warmed up by the light, which is conducive to the growth of natural food organisms and crab growth. In order to maintain good water quality, add water once every 3-5 days and add 5 to 10 cm of water each time. If water quality is found to be deteriorating, change the water promptly. It is also necessary to prevent water snakes, frogs, etc. from entering the rearing pond to harm the crabs. After 20-40 days of cultivation, the ability of juvenile crabs is greatly enhanced. At this time, catching another pool can continue to cultivate juvenile crabs or directly cultivate crabs.
The three types of crab cultivation methods have their own advantages. The use of net cages for rearing crabs, due to convenient exchange of water, high dissolved oxygen in water, high density of crab seedlings, rapid development of young crabs, high survival rate; cement ponds cultivate crabs, stocking densities are also larger, can save cultivation pond Area, crabs are also more convenient to catch; soil ponds cultivate crabs, the operation is relatively simple, and some can be slightly modified fish ponds, fish ponds can be used to cultivate crabs. After the crab cultivation stage, the survival rate of the 3 stage crabs is generally 30% - 40%, and the survival rate of the 5 stage crabs can reach 30%.
4. After the young crabs have been cultivated with cages, concrete tanks or earthen ponds, the size of the out-of-carton (pool) is generally 3,000-5,000/kg. In order to further improve the survival rate, crabs are often cultivated into 100-200. Only / kg of juvenile crabs, ie species of crabs or "cuckoo crabs". Juvenile crabs are cultivated in ponds.
1. Juvenile Crab Pool Conditions: The area is generally 700-2000 square meters, and the pool depth is about 1.5 meters. It requires sufficient water, good water quality, convenient injection and drainage, and less silt at the bottom of the pool. In order to facilitate catching juvenile crabs, one end of the bottom of the pool is inclined from the outlet end to the outlet end, and the height difference between the two ends is 10-15 cm. Young crabs should be built around the escape facilities.
2. Clearing, disinfecting, and planting grass: Ponds that are prepared to raise young crabs should thoroughly remove carnivorous, omnivorous fish, and frogs. Before the crumb crabs are released, they must be sterilized 7-10 days before they are put into use. When water is added one week later, wild fish should be prevented from entering the pool. The bottom of the pond should be planted with aquatic plants, Vallisneria, Hydrilla verticillata, and Malay Oozi. Can also be transplanted water hyacinth, water peanuts, water lettuce, etc., coverage should be around 30%. Aquatic grass can provide a hidden environment for crabs, but it can also be used as a part of feed. It can also put some broken tiles in the bottom of the pool for crabs to inhabit.
3, crabs put: specifications 3000-5000 / kg of crabs, each 667 square meters can be put 3-4 million, 8-10 kg, put 45-60 per square meter. After 4-5 months of incubation, the discharge specifications can reach 5-8 grams, that is, 120-200/kg.
4. Feeding management: Juvenile crab breeding is in the hot season from June to September. It is very important to eat well and have frequent activities.
1 Feeding: The feed should be fresh, palatable and evenly fed. In the early and late stages, some animal feeds can be fed as appropriate, and in the middle period, plant-based feeds should be used. Animal and vegetable feeds should be properly matched and fed. Daily feeding accounts for 5% - 10% of body weight. To set up a feed station, a combination of spot feeding and dispersion feeding. To feed the feed on the water line, the main feeding in the evening.
2 Pay close attention to changes in water quality so that the dissolved oxygen in the water is kept above 5 mg/l. It is necessary to add water or change the water frequently. Normally, add water once every 3-5 days. Each time you deepen 10-15 cm, if you change the water, you can first drain the pool water by 1/4-1/3 and add new water. It is necessary to maintain good water quality and to make the water level relatively stable. At the same time, lime is used every 15 to 20 days in the summer. Each dose of 667 square meters is 10-15 kilograms, which can prevent disease and supplement calcium, which is beneficial to the shelling of juvenile crabs.
3 daily management: to do a good job of preventing flight, preventing disease, and preventing predators. Should pay attention to the patrol pond, find problems and take measures to solve them. According to the development of young crabs, timely adjustment of feeding amount.
The quality of crab seedlings directly affects the results of larval rearing. It is also one of the keys to the success or failure of adult crab breeding. Therefore, we must choose natural crabs in the Yangtze River Estuary or crabs artificially propagated in the Yangtze River water system. In the specific selection of crab, you can pay attention to the following aspects:
The first is to see the color. High-quality crab seedlings are generally light yellow or gray-gray, with bright color;
The second is to look at vitality. High-quality crab seedlings are full of vitality, quickly spread by hand after being loosened, and quickly swam around in water;
The third is to see the specifications. High-quality crab seedlings have the same specifications and uniform size, generally no more than 160,000 per kilogram;
The fourth is to look at impurities. High-quality crab seedlings should contain no impurities and no dead seedlings;
The fifth is to look down on the time. In artificially propagated crab seedlings, more than 80% of the juveniles grow into large ocular larvae and begin to fade. The dilution time is generally not less than 100 hours.
Here are some ways to cultivate young and young crabs.
First, cages to cultivate crabs
1, the production of cages: nets can be used polyethylene mesh or nylon sieve, length, width, height were 2,1,1 meters, or 4,2,1 meters, or 4,3,1 meters, net Head 0.8-1 mm. The cage is supported with bamboo, etc., to open the box. The cage should be covered, and a door that can be opened and closed at the junction between the cover and the side of the box should be closed. The zipper should be sewn and closed normally.
2, cage settings: cages should be located in non-polluting lakes, reservoirs, rivers, or deeper ponds, preferably with micro-flowing water, in order to maintain a high level of dissolved oxygen. About 20 cm of the box is exposed above the water, 80 cm sinks into the water, and the box is 3 to 5 meters away. Water hyacinths, water lettuces, water peanuts and other plants should be placed inside the box, which generally accounts for about one-half of the area inside the box, or about 1 kilogram of fresh grass per square meter, making it easy for the crabs to attach and inhabit.
3, crab seedlings: different areas, different stocking densities at different times, the density of 0-2 million per square meter, ranging from about 10,000 per square meter.
4. Feeding: The basic requirement is that the bait nutrition should be rich and fresh, and the particle size must be in the middle, and the quantity of the feed should be sufficient. Optional soy milk, egg yolk, can also be used to process finely broken snails, quail meat, or granular feed crushing feed, you can also fish out zooplankton (red worms), leeches and other feeding. Feeding 3 to 4 times a day, the daily feeding amount can account for about 50% of the body weight of the crabs. With the continuous growth of the crabs, the latter can account for 10% to 15% of the body weight. The bait should be sprinkled on the stems and leaves of water plants and be distributed evenly.
5, daily management: To check whether the cage is damaged, to prevent fleeing seedlings. Regularly wash the net to prevent it from clogging the mesh and make the exchange of water inside and outside the box unsmooth. To prevent water mice, water snakes, etc. into the box to harm crabs. After 20-40 days of cultivation, crab seedlings develop into 3-5-phase juvenile crabs. Harvest them in time and transfer them to earthen ponds to raise juvenile crabs in order to avoid disparities in the size of the boxes and the occurrence of similar disability and affect the survival rate.
Second, the cement pool to raise crabs
1. Cement pool conditions: The area is generally more than 10 square meters, less than 100 square meters, the depth of the pool is about 1 meter, and the pool-shaped square can be round. Water quality should be fresh and water should be sufficient. The pool should have inlets and outlets and be blocked with mesh cloth to avoid fleeing seedlings. At the bottom of the pool, you can put some broken bricks and tiles, and then put in water plants to make it easier for crabs to inhabit. The upper part of the pool wall should be smooth, and the pool should be covered with plastic film to prevent escape.
2, cement pool disinfection and fertilization: The new cement pool should be soaked with water for several days, and repeatedly change the water before the release of crab seedlings, the old pool before putting the seedlings to wash with 100ppm bleach solution again, 5-7 days after the water injection 40--50 cm, appropriate amount of fertilizer, pre-incubation of plankton, to prepare a good ecological environment and bait foundation for crab seedlings.
3, crab seedlings: cement ponds with normal conditions, 5000-6000 can be placed per square meter, better conditions, can often change the water or cement pool can keep micro-water, crabs per square meter can be put 10,000 about.
4. Feeding and management: Although crab seedlings cultivated plankton before fertilization, they could not meet the needs of growth and development of crabs, but also fed certain nutrient-rich baits. Every day can be divided into 2 - 3 times splash soy milk, soy flour, fish meal and other bait, the daily feeding amount is about 20% - 30% of the weight of crabs. Pay attention to spread evenly and cast more on the leaves of aquatic plants. The water is shallow at the beginning. In order to maintain rich dissolved oxygen and good water quality, it is often necessary to add water or change water. In the later stages of cultivation, the depth of pool water can gradually be added to 70-80 cm.
Third, the earth pond nurtures crabs
1, soil conditions: the area should not be too large, a few hundred square meters to thousands of square meters is better, the pool depth of about 1 meter, can maintain a depth of 70 - 80 cm. Long shape is better. The bottom of the pool is required to be flat, with less silt, no water leakage, solid pool floor, adequate water supply, good water quality, and easy access to water.
2, earthen pond disinfection: 15-20 days before the release of crab seedlings, drain the pool water, first make the bottom of the pool, then the orange juice (7)?铩I 矣昧 矣昧 旱 旱 旱 旱 旱 旱 旱 旱 . .. 5 meters, 60-80 kilograms per 667 square meters. With bleach, the pool water concentration is 20 ppm. The drug should be fully stirred and evenly spilled.
3, fertilization: Crab seedlings 5-7 days before the next tank, fertilizer should be applied to cultivate food organisms so that the crabs after the pond is a palatable natural food. Generally, 150-200 kilograms of fermented cow dung, pig dung, human waste, etc. can be applied per 667 square meters.
4, the release of crabs: crab seeding density, according to soil conditions, feeding conditions, out of the pool specifications and management level and other factors to determine, the current general every 667 square meters of crab seedlings 1.5-2 kg, good conditions can be Put 2-3 kg.
Due to the large area of ​​the earthen pond, it is difficult to evenly feed the fish. The crabs in the later period are often of great disparity. Therefore, the same batch of crabs should be placed in each pond, and the specifications must be the same.
5. Feeding and management: Crab seedlings and water ponds can use some natural foods, but it is difficult to meet the needs of the whole growing season. Pre-feeding can be mainly soybean milk, egg yolk, and fish gizzards. After one week, feed varieties can be expanded to bean cakes, wheat bran, small fish, shrimp, snail meat, and quail, etc. The feeds are ground and added into a paste. Sprinkle evenly in the early stage, and feed it along the earth pond at a certain point. Put the feed on shallow water or aquatic plants and other attachments. The amount of daily feeding can be controlled by 10% - 15% of the total weight of larvae, and it can be adjusted to about 10% in the later period. Every day from 7 to 8 in the morning and from 6 to 7 in the evening, the feeding is once in the evening, and the feeding amount can be 60% to 70%. The specific amount of feed per day depends on the food intake and weather conditions of the crabs.
When the crabs are in the pool, the pool water can be kept at about 50 cm. The pool water is warmed up by the light, which is conducive to the growth of natural food organisms and crab growth. In order to maintain good water quality, add water once every 3-5 days and add 5 to 10 cm of water each time. If water quality is found to be deteriorating, change the water promptly. It is also necessary to prevent water snakes, frogs, etc. from entering the rearing pond to harm the crabs. After 20-40 days of cultivation, the ability of juvenile crabs is greatly enhanced. At this time, catching another pool can continue to cultivate juvenile crabs or directly cultivate crabs.
The three types of crab cultivation methods have their own advantages. The use of net cages for rearing crabs, due to convenient exchange of water, high dissolved oxygen in water, high density of crab seedlings, rapid development of young crabs, high survival rate; cement ponds cultivate crabs, stocking densities are also larger, can save cultivation pond Area, crabs are also more convenient to catch; soil ponds cultivate crabs, the operation is relatively simple, and some can be slightly modified fish ponds, fish ponds can be used to cultivate crabs. After the crab cultivation stage, the survival rate of the 3 stage crabs is generally 30% - 40%, and the survival rate of the 5 stage crabs can reach 30%.
4. After the young crabs have been cultivated with cages, concrete tanks or earthen ponds, the size of the out-of-carton (pool) is generally 3,000-5,000/kg. In order to further improve the survival rate, crabs are often cultivated into 100-200. Only / kg of juvenile crabs, ie species of crabs or "cuckoo crabs". Juvenile crabs are cultivated in ponds.
1. Juvenile Crab Pool Conditions: The area is generally 700-2000 square meters, and the pool depth is about 1.5 meters. It requires sufficient water, good water quality, convenient injection and drainage, and less silt at the bottom of the pool. In order to facilitate catching juvenile crabs, one end of the bottom of the pool is inclined from the outlet end to the outlet end, and the height difference between the two ends is 10-15 cm. Young crabs should be built around the escape facilities.
2. Clearing, disinfecting, and planting grass: Ponds that are prepared to raise young crabs should thoroughly remove carnivorous, omnivorous fish, and frogs. Before the crumb crabs are released, they must be sterilized 7-10 days before they are put into use. When water is added one week later, wild fish should be prevented from entering the pool. The bottom of the pond should be planted with aquatic plants, Vallisneria, Hydrilla verticillata, and Malay Oozi. Can also be transplanted water hyacinth, water peanuts, water lettuce, etc., coverage should be around 30%. Aquatic grass can provide a hidden environment for crabs, but it can also be used as a part of feed. It can also put some broken tiles in the bottom of the pool for crabs to inhabit.
3, crabs put: specifications 3000-5000 / kg of crabs, each 667 square meters can be put 3-4 million, 8-10 kg, put 45-60 per square meter. After 4-5 months of incubation, the discharge specifications can reach 5-8 grams, that is, 120-200/kg.
4. Feeding management: Juvenile crab breeding is in the hot season from June to September. It is very important to eat well and have frequent activities.
1 Feeding: The feed should be fresh, palatable and evenly fed. In the early and late stages, some animal feeds can be fed as appropriate, and in the middle period, plant-based feeds should be used. Animal and vegetable feeds should be properly matched and fed. Daily feeding accounts for 5% - 10% of body weight. To set up a feed station, a combination of spot feeding and dispersion feeding. To feed the feed on the water line, the main feeding in the evening.
2 Pay close attention to changes in water quality so that the dissolved oxygen in the water is kept above 5 mg/l. It is necessary to add water or change the water frequently. Normally, add water once every 3-5 days. Each time you deepen 10-15 cm, if you change the water, you can first drain the pool water by 1/4-1/3 and add new water. It is necessary to maintain good water quality and to make the water level relatively stable. At the same time, lime is used every 15 to 20 days in the summer. Each dose of 667 square meters is 10-15 kilograms, which can prevent disease and supplement calcium, which is beneficial to the shelling of juvenile crabs.
3 daily management: to do a good job of preventing flight, preventing disease, and preventing predators. Should pay attention to the patrol pond, find problems and take measures to solve them. According to the development of young crabs, timely adjustment of feeding amount.
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