The large water surface crab breeding has the characteristics of simplicity, low investment, quick effect, high yield, and has broad prospects for promotion in our province. Combining with the actual situation of breeding crabs in our province, the crab water surface culture technology is introduced as follows:
First, the main biological characteristics of crab
1, living habits
The life of crabs is about two years. Most of the time they live in fresh water, but when they are breeding, the crabs swim to the estuary to spawn in the shallow sea. The life of crabs goes through five stages: fertilized eggs, zoea, large-eyed larvae, juvenile crabs and adult crabs. There are differences in living habits at all stages. In the zoea stage, it is necessary to live in brackish or salt water environments. After the juveniles become big-eyed larvae, they enter the stage of crabs, transition from planktonic life to swimming, and can crawl and land. They can leave the seawater environment and live in freshwater waters. Large-eyed larvae metamorphose into young crabs. After the crabs are grown, they reach the crabs, which mainly live in fresh water and inhabit the caves under the water.
2, diet
The crabs feed on phytoplankton algae in the early stage of zoea and gradually turn into omnivorous animals. They prefer animal feeds such as fish, shrimp, snails, cockroaches, cockroaches, worms, aquatic insects, and the like. The body is of particular interest. However, in natural waters, plant feeds are more easily obtained than animal feeds. Therefore, plant feeds in the stomach of river crabs account for a major part, such as reeds, black seaweeds, barnyard grasses, Vallisneria and small water algae.
3, shell and growth
The crabs go through many oyster shells throughout their lives. The life of crabs is roughly 18 times that of shells. After each oyster shell, crabs increase in size and weight subsequently increases.
4, reproduction
Generally after the fall of September, mature crabs begin sexual reproduction after sexual maturity, and follow the river downstream to the estuary shallow sea. The end of October to the second year of March each year is the spawning period of crabs. When the water temperature is above 8°C, crabs spawn and lay eggs. Artificial breeding is to place mature crabs caught in artificially prepared seawater to facilitate their spawning.
Second, the river crab breeding technology
The artificial breeding of crabs can be divided into three breeding sections: artificial breeding, crab breeding, and crab breeding. The farming section for large water surface in our province is crab breeding, which is the development of young crabs with a size of 80-240/kg. Specifications 6 to 10/kg commercial crabs.
1, the choice of breeding waters
Fresh water, pollution-free water, stable water levels, abundant aquatic plants, and lakes and reservoirs with large snails should be selected for aquaculture. Few plants can be planted artificially. There are few snails and can be put in manually. Shallow lakes and reservoirs have good aquaculture effects.
2, crab species stocking
1) Quality requirements for crab species
Buying a good crab species is a key part of breeding crabs. Crab species require uniform specifications, moderate size, complete appendages, and robust physique. How to identify the quality of crab species depends on body color. Crab species that have not been exposed to water for a short period of time or in the absence of water have better shades of gray and bright shells. If the crab species is left in water for a long time, it will lead to serious water loss in the body, making the back carapace pale and pale yellow. Although this species of crab is not dead, it will gradually die after stocking. The second is to watch activities. Crab species are active in crawling, moving freely and lively. Turning crabs can turn over immediately. You can also grab a handful of crabs and put them on the ground. If you see the crab species fleeing immediately, it is a good crab species. The third is to look at the body and see if the chewing foot and step foot are complete and if there is any damage.
2) Crab transportation
Crab species are transported in the spring of April. The transportation of crab species must be able to master the four technical keys of low temperature 5 to 10°C, ventilation, humidity, and prevention of crab species activity. The specific method is to first place the crabs to be transported in crab cages or sealable cages, and then put them in rivers or micro-flowing water. After 4 to 6 hours of raising, they will empty the intestines and empty the stools. The crabs are placed in a soaked Pouch or a 60cm40cm polyethylene mesh bag, and the crabs are back up. Generally, about 15kg of crabs are packaged per pouch, and the polyethylene mesh bags can be loaded with crab seeds of 5 to 10kg and then fastened. Put bamboo baskets or foam boxes of the same size and the pockets must be tight so that crabs cannot move within the bags. Foam boxes are to be drilled in the walls of the box for ventilation. Transport vehicles can use cars and trains. Before loading the car, lay a layer of grass in the car and wet it with water. Prevent wind during transport. In the temperature of 5 ~ 10 °C transportation, as long as the ventilation, moist environment, 24 hours without opening the package view, the survival rate of transport up to 95%%.
3) Stocking Density and Stocking Methods
Crab species requirements 80 ~ 240 / kg, this size of crab species also known as crabs. Open 10 to 20 crabs per mu. Before stocking, the first crab will be treated with slow-release seedlings. The crab will be soaked in water together with net bags for 1 to 2 minutes, removed and placed in the air for 3 to 5 minutes. This is repeated 2 or 3 times until the crabs are fully absorbed. After adapting to the water environment, crabs are stocked on a boat for stocking. The stocking sites should be far away from the outlets, and they should be selected for more stockpiling, small waves, and rich natural lakes in the Huku Bay. When stocking, pour the crabs from the bag on the boat, let the crabs climb into the water, put them as evenly as possible and enlarge the range.
3, daily management
Double barriers are installed at the water inlet and outlet to prevent escape. Barriers can use polyethylene mesh or wire mesh. Always check if there are any holes in the block, and repair them if necessary. During the flood season, it is necessary to pay attention to the management of the anti-escape equipment and prevent the flood from destroying the escape prevention equipment. During the crab growth period, it is forbidden to sow grass and ducks are forbidden. Fishing nets are prohibited from fishing. Take care to prevent sewage containing organophosphorus or pyrethroids from entering the waters, and do not use such drugs in waters.
4, crab fishing
It is usually harvested from the end of August to the beginning of September. If fishing is too late, mature crabs will escape outwards and engage in reproductive migration. Therefore, fishing must catch up with the natural reproduction of crabs before the concentration of force to catch, usually with cages and crabs ecstasy array fixed arrest, you can also use wire mesh, take crabs every evening or morning, repeated, and the fishing effect is good. In the sexual maturation season, the crabs must crawl and feed on the beach at night, or they can be used for reproduction and crawling. At this time, humans can be organized to use light trapping, touring and capturing, and to carry out many times.
1) Crab fishing: Crab turtle, also known as the sect, is a common fishing tool suitable for large-scale catching of crabs in shallow lakes and reservoirs. It uses a net wall as a guide net to induce crabs into the net bags. The net bag has 7 to 10 knots and is about 10 meters long. It has large imports and small outlets. It is round or square and sinks to the bottom of the water. Each section of the entrance has floating nets that can not be entered. The mesh bag is fixed at the mouth of the net wall, and the crabs in the mesh bag can be poured once each morning and evening.
2) Earthworm fishing: Earthworm is also a common fishing net. It has many festivals, ranging in length from 10 meters to tens of meters. It has a rectangular shape. Each section has an entrance and it can't enter. After a few festivals, there is a mesh bag and the crabs finally enter the net bag when fishing. When catching crabs, sink the ground dragon into the bottom of the water and use a float as a mark. The crabs in the net bag can be poured one at a time in the morning and evening. After the crabs are poured out, the bags are tied and put back into place.
3) Screen fishing: The screen is also called gill net and hanging net. Generally, each net length is 50 meters, net height is about 1 meter, and mesh size is 6 to 5 to 8 centimeters. From 3 to 4 in the afternoon, the network will be released. Every 1 to 2 hours, the net will be taken for crab once. The net will be closed in the morning and the crabs will be finished. Take care when removing crabs on the net to avoid tearing the nets.
First, the main biological characteristics of crab
1, living habits
The life of crabs is about two years. Most of the time they live in fresh water, but when they are breeding, the crabs swim to the estuary to spawn in the shallow sea. The life of crabs goes through five stages: fertilized eggs, zoea, large-eyed larvae, juvenile crabs and adult crabs. There are differences in living habits at all stages. In the zoea stage, it is necessary to live in brackish or salt water environments. After the juveniles become big-eyed larvae, they enter the stage of crabs, transition from planktonic life to swimming, and can crawl and land. They can leave the seawater environment and live in freshwater waters. Large-eyed larvae metamorphose into young crabs. After the crabs are grown, they reach the crabs, which mainly live in fresh water and inhabit the caves under the water.
2, diet
The crabs feed on phytoplankton algae in the early stage of zoea and gradually turn into omnivorous animals. They prefer animal feeds such as fish, shrimp, snails, cockroaches, cockroaches, worms, aquatic insects, and the like. The body is of particular interest. However, in natural waters, plant feeds are more easily obtained than animal feeds. Therefore, plant feeds in the stomach of river crabs account for a major part, such as reeds, black seaweeds, barnyard grasses, Vallisneria and small water algae.
3, shell and growth
The crabs go through many oyster shells throughout their lives. The life of crabs is roughly 18 times that of shells. After each oyster shell, crabs increase in size and weight subsequently increases.
4, reproduction
Generally after the fall of September, mature crabs begin sexual reproduction after sexual maturity, and follow the river downstream to the estuary shallow sea. The end of October to the second year of March each year is the spawning period of crabs. When the water temperature is above 8°C, crabs spawn and lay eggs. Artificial breeding is to place mature crabs caught in artificially prepared seawater to facilitate their spawning.
Second, the river crab breeding technology
The artificial breeding of crabs can be divided into three breeding sections: artificial breeding, crab breeding, and crab breeding. The farming section for large water surface in our province is crab breeding, which is the development of young crabs with a size of 80-240/kg. Specifications 6 to 10/kg commercial crabs.
1, the choice of breeding waters
Fresh water, pollution-free water, stable water levels, abundant aquatic plants, and lakes and reservoirs with large snails should be selected for aquaculture. Few plants can be planted artificially. There are few snails and can be put in manually. Shallow lakes and reservoirs have good aquaculture effects.
2, crab species stocking
1) Quality requirements for crab species
Buying a good crab species is a key part of breeding crabs. Crab species require uniform specifications, moderate size, complete appendages, and robust physique. How to identify the quality of crab species depends on body color. Crab species that have not been exposed to water for a short period of time or in the absence of water have better shades of gray and bright shells. If the crab species is left in water for a long time, it will lead to serious water loss in the body, making the back carapace pale and pale yellow. Although this species of crab is not dead, it will gradually die after stocking. The second is to watch activities. Crab species are active in crawling, moving freely and lively. Turning crabs can turn over immediately. You can also grab a handful of crabs and put them on the ground. If you see the crab species fleeing immediately, it is a good crab species. The third is to look at the body and see if the chewing foot and step foot are complete and if there is any damage.
2) Crab transportation
Crab species are transported in the spring of April. The transportation of crab species must be able to master the four technical keys of low temperature 5 to 10°C, ventilation, humidity, and prevention of crab species activity. The specific method is to first place the crabs to be transported in crab cages or sealable cages, and then put them in rivers or micro-flowing water. After 4 to 6 hours of raising, they will empty the intestines and empty the stools. The crabs are placed in a soaked Pouch or a 60cm40cm polyethylene mesh bag, and the crabs are back up. Generally, about 15kg of crabs are packaged per pouch, and the polyethylene mesh bags can be loaded with crab seeds of 5 to 10kg and then fastened. Put bamboo baskets or foam boxes of the same size and the pockets must be tight so that crabs cannot move within the bags. Foam boxes are to be drilled in the walls of the box for ventilation. Transport vehicles can use cars and trains. Before loading the car, lay a layer of grass in the car and wet it with water. Prevent wind during transport. In the temperature of 5 ~ 10 °C transportation, as long as the ventilation, moist environment, 24 hours without opening the package view, the survival rate of transport up to 95%%.
3) Stocking Density and Stocking Methods
Crab species requirements 80 ~ 240 / kg, this size of crab species also known as crabs. Open 10 to 20 crabs per mu. Before stocking, the first crab will be treated with slow-release seedlings. The crab will be soaked in water together with net bags for 1 to 2 minutes, removed and placed in the air for 3 to 5 minutes. This is repeated 2 or 3 times until the crabs are fully absorbed. After adapting to the water environment, crabs are stocked on a boat for stocking. The stocking sites should be far away from the outlets, and they should be selected for more stockpiling, small waves, and rich natural lakes in the Huku Bay. When stocking, pour the crabs from the bag on the boat, let the crabs climb into the water, put them as evenly as possible and enlarge the range.
3, daily management
Double barriers are installed at the water inlet and outlet to prevent escape. Barriers can use polyethylene mesh or wire mesh. Always check if there are any holes in the block, and repair them if necessary. During the flood season, it is necessary to pay attention to the management of the anti-escape equipment and prevent the flood from destroying the escape prevention equipment. During the crab growth period, it is forbidden to sow grass and ducks are forbidden. Fishing nets are prohibited from fishing. Take care to prevent sewage containing organophosphorus or pyrethroids from entering the waters, and do not use such drugs in waters.
4, crab fishing
It is usually harvested from the end of August to the beginning of September. If fishing is too late, mature crabs will escape outwards and engage in reproductive migration. Therefore, fishing must catch up with the natural reproduction of crabs before the concentration of force to catch, usually with cages and crabs ecstasy array fixed arrest, you can also use wire mesh, take crabs every evening or morning, repeated, and the fishing effect is good. In the sexual maturation season, the crabs must crawl and feed on the beach at night, or they can be used for reproduction and crawling. At this time, humans can be organized to use light trapping, touring and capturing, and to carry out many times.
1) Crab fishing: Crab turtle, also known as the sect, is a common fishing tool suitable for large-scale catching of crabs in shallow lakes and reservoirs. It uses a net wall as a guide net to induce crabs into the net bags. The net bag has 7 to 10 knots and is about 10 meters long. It has large imports and small outlets. It is round or square and sinks to the bottom of the water. Each section of the entrance has floating nets that can not be entered. The mesh bag is fixed at the mouth of the net wall, and the crabs in the mesh bag can be poured once each morning and evening.
2) Earthworm fishing: Earthworm is also a common fishing net. It has many festivals, ranging in length from 10 meters to tens of meters. It has a rectangular shape. Each section has an entrance and it can't enter. After a few festivals, there is a mesh bag and the crabs finally enter the net bag when fishing. When catching crabs, sink the ground dragon into the bottom of the water and use a float as a mark. The crabs in the net bag can be poured one at a time in the morning and evening. After the crabs are poured out, the bags are tied and put back into place.
3) Screen fishing: The screen is also called gill net and hanging net. Generally, each net length is 50 meters, net height is about 1 meter, and mesh size is 6 to 5 to 8 centimeters. From 3 to 4 in the afternoon, the network will be released. Every 1 to 2 hours, the net will be taken for crab once. The net will be closed in the morning and the crabs will be finished. Take care when removing crabs on the net to avoid tearing the nets.
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