With the deepening of the adjustment of the agricultural industry structure, some rivers and lakes along the river have begun to “return fields and return lakes†in order to protect the ecology, and changed rice to raise crabs. To this end, from 2000 to 2001, we conducted a large-scale Crab breeding experiment using low lake field (lowland paddy field) at Lugu Lake, Zhouchengyu Fishery Yard in Jianli County, Hubei Province, and achieved good economic and ecological benefits. Basically mature.
I. Selection of Hutian Low Hutian is a farmland formed by farmland around the lake in the “grain-based†era, and its low-lying terrain makes it easy to form water. Therefore, the following points must be taken into consideration when selecting low lake fields for crab cultivation: First, there must be plenty of water, good water quality, no pollution, easy access to water and drainage, and drought, irrigation, and drainage. Second, the bottoms of low lake fields should be hard sandy. Soil; Third, the dike is strong, not easy to be storms across, embankment can be more than 2m water conservation; Fourth, to facilitate the transportation, vehicles, boats can be directly to the farming Hutian; Fifth, there is sufficient power for timely access, drainage.
2. Anti-escaping Polyethylene nets are embedded in the dike around the lake. The net height is about 50cm. A 30cm wide hard plastic film is sewn on the upper part of the net; cone-shaped anti-escape nets are installed at the inlet and outlet valves. Near the inlet and outlet, set 2 to 3 blocks on the inside to prevent crabs from fleeing.
3. Qinghu Lake Due to the accumulation of water all year round in the low lake fields, there are a large number of wild black locusts, stingrays and yellow locusts in the lake fields. They must be cleared of lakes before they are released to remove these harmful Fish. The specific measures are: pump the stagnant water in the lake to the lowest water level, use electric catching method to kill the fish as much as possible, and then use 100 ml of “clean pond net†every 6 mu to kill the fish once.
Fourth, to create a suitable ecological environment According to the living characteristics of river crabs in natural lakes, namely: crabs like to live in waters with fresh water, high transparency, rich dissolved oxygen, underlying grasses and a large number of benthos and water depth of about 2m. Low Lake Tanaka artificially creates a suitable ecological environment for his life and promotes the rapid growth of crabs.
1. Cultivate and transplant high-quality aquatic plants to remove harmful aquatic plants.
The quality of aquatic plants is not only a good food for crabs, but also a place for crabs to inhabit, avoid their enemies, and clam shells. It can also improve water quality and increase dissolved oxygen in water. It can also play a role in cooling summers and promoting the growth of crabs. To raise crabs in low lake fields, it is necessary to cultivate high-quality wild aquatic plants and also to transplant high-quality aquatic plants.
Natural lowland Tianzhong itself grows some high-quality wild aquatic plants such as goldfish algae, Hydrilla verticillata, Malay-eyed vegetables, â– grass (oil strips), philodendron (water peanuts), and pristine grasses. These plants are lakes The main water plants, which account for 80% of the total amount of aquatic weeds, should guarantee the growth and reproduction of these plants.
While ensuring the rapid growth of wild aquatic plants in the lake, it is also necessary to transplant some high quality aquatic plants like crabs. One is planting Vallisneria using the method of seeding. Vallisneria, also known as noodles, duck tongue grass, and leek grass, is a typical submerged plant. It is one of the aquatic plants that the crabs like to eat. The seeds are small, the seeds are wrapped in the grass clips, and soaked in water for 10 to 15 minutes before sowing. Then, the grass seed is pulled out with a sampan, and the soil and grass seeds are mixed well and then sowing can be performed. Each kilogram of grass seeds can be sown with 5 to 8 acres. The second is the use of sowing method for the transplanting of goldfish and black-green algae, that is, from the rivers and large lakes to take gold algae or black algae, and then cut it into small pieces of about 15cm, and then spread it into the lake, per acre Grass 10kg to 15kg.
In the crab breeding process, the growth height of aquatic weeds should be controlled to avoid growing out of the water surface. If water grows out of the lake, it will directly affect the light in the lake and the exchange of water in the upper and lower layers, resulting in a decrease in water temperature and a decrease in dissolved oxygen, which is not conducive to normality of crabs. Grow. Therefore, always keep the height of the water below 30cm above the water surface. If you exceed this height, you must cut off the height. While transplanting high quality aquatic weeds, we remove harmful water plants such as water chestnuts, water chestnuts, and lotus leaf that affect light and water quality in lake fields.
2. Transplant snails.
Snails are a type of shellfish and live food for crabs. Living snails can not only ingest benthic algae and organic debris in the bottom of the lake, but also improve water quality. After the snails are released, some snails that have not been ingested can also reproduce, increase the number of live baits, and have multiple functions. From March to June, it is the season of snail breeding, and its body harbors a lot of young snails. At this time, transplanting snails is not only conducive to the breeding of snails, but also meets the needs of juvenile snails and crabs to take up juvenile snails. When transplanting, put snail 200-300kg per acre is appropriate.
Fifth, seed selection and delivery
1. Seed selection.
At present, China has formed a large-scale production of crab crabs mainly Liao crab and Yangtze crab, followed by Minjiang crab and Yellow River Crab. Because these crabs grow in different water systems for a long time, the natural environment is quite different. Therefore, the growth rules of crabs in different river systems have their own characteristics. The crab grows fast, has a short life cycle, matures early, comes into the market early, and concentrates on fishing (this also applies to farming in the South). The Yangtze River Crab also grows fast, but has a long life cycle, is late in its maturity, and is listed late for fishing. In order to increase economic efficiency, it is easy to decentralise the market and raise the selling price. Most crabs are selected as breeding objects when raising crabs in low lake fields. When selecting the Yangtze River crab, generally grasp the following principles: (1) fast growth, large specifications. (2) No disease, no residue, and strong physique. (3) crawling against water faster.
2. Stage seedlings.
The seedlings are planted in stages. The "round catch and release" is a set of effective crab cultivation methods that we have concluded during the crab cultivation in low lake fields. After the lake fields have been cultivated in mid-April each year, when the water temperature exceeds 18°C, they are released. When the Yangtze River crabs were bred early in the year, the specifications were generally around 10,000/kg, and 400 to 500 animals were released per mu. Because the individual crabs are small and easy to be attacked by predators, after the crabs are transported, they must first be put into the lake and surrounded by polyethylene nets to be raised in the holding area. The density of the crabs is 20,000 or so per mu. Feed the cooked, small-sized fish in a timely manner and feed it at 20% of the body weight of the crabs. When the crabs grow to 1000/kg, the fence is removed and the crabs spread to the entire lake. In early July, conventional Yangtze River crabs will be released again. The specifications will be 8,000 birds per kg, and 400 to 500 animals per acre will be thrown directly into the lake to cultivate large-sized crab species and no longer reared. When crabs are caught in the fall, the seeds are left in the lake. Using this breeding method, a batch of commercial crabs can be harvested in the same year, and a batch of large-sized crab species can also be cultivated. Such crab species have strong adaptability to the environment and high survival rate, and can produce large-size commercial crabs in the following year.
Six, water quality control
1. Control the water depth and adjust the water temperature.
In the process of crab cultivation, different water depths are controlled at different growth stages to facilitate the normal development and growth of crabs. In spring, the temperature is low, the water depth is controlled to 0.5m, and sunlight can directly reach the bottom of the lake. The water temperature rises quickly, which is beneficial to the growth of aquatic plants and the recovery of river crabs. We know that the suitable growth temperature for crabs is 15°C to 30°C, and the optimum growth temperature is 25°C to 28°C. When the water temperature is above 33°C, it stops feeding and is in a semi-conscious state. Therefore, when summer arrives and the temperature and water temperature are high, water injection into the lake is started so that the water depth gradually reaches about 2m. In this way, even in the hot summer months when the surface water temperature is 35°C, the bottom water temperature of the lake can still be maintained at about 28°C, thus ensuring the normal feeding and growth of crabs. In autumn, the water depth in the lake remains about 2.0m. This water temperature is constant, and it is not susceptible to cold currents and cooling. It can ensure that the crab has a water environment for smooth growth and fattening. In winter, crabs and fish are netted and immediately added to 0.5m to 0.7m to facilitate safe wintering.
2. Lime splashes regulate water quality.
In the process of raising crabs, during the high-temperature season from June to August, the lime is sprinkled into the lake once every 20 days. Each time, 6 kg per acre is spilled. Lime and lime can improve water quality and increase the transparency of water. Secondly, it can increase the concentration of calcium ions, and facilitate the absorption of crabs and clam shells. Thirdly, it can increase the pH of water bodies (because the water in the lake fields is acidic), and it has many effects.
3. Increase the volume of water exchange.
After entering the summer, water is first injected into the lake, and drainage begins when the water depth reaches 2m. By adopting the “edge-to-edge†approach, the entire body of water in the lake will become alive, basically forming a pattern of running water and raising crabs. This will not only be beneficial to the growth of crabs and increase the total output, but will also reduce the occurrence of diseases in the breeding process.
7. The feeding of bait feed should follow the principle of “pre-rough, medium-green, and later-fineâ€. The previous period (before May) was the initial release and recovery period of crabs. The bait was mainly used to cultivate aquatic plants and put snails. The crabs mainly ingest aquatic plants and tender grasses. Wild fish eggs and flies on leaves and aquatic plants. The mid-term (June-August) is a hot season. At this time, feeding animal feeds tends to spoil the water quality. Therefore, aquatic grasses and transplanted snails are still the dominant species in this period. With the end of the high-temperature season, the water temperature gradually drops to 28°C. Below, the river crab enters the suitable temperature growth period, at this time must mix with feeds some wheat, corn, soybean, broad bean and other plant foods. In the later period, generally after September, the crabs begin to mature their shells for the last time. At the same time, they also enter the fattening and rapid weight gain stages. At this time, they are required to feed some low-value fish and other animal foods while feeding plant foods to strengthen nutrition. To increase crab production and specifications.
VIII. Injury First, catch fish. Although crabs have been sterilized prior to their release, they are sometimes not removed. Therefore, the wild fish in the lake must be further fished after the spring season. According to the habit of yellow sturgeons preferring to inhabit and hunt deeper around the lake, the stingrays are used to remove the stingrays from the lake; according to the behavior of the yellow sturgeon preferring to prey on the watery areas of the lake, it is used in the grass. The method of burying the fish larvae catches the yellow cricket; according to the breeding habits of the quail, the quail eggs are floating on the water for hatching after the pupa are laid, while the brooding fish of the male and female of the black locust ambush under the fertilized eggs to care for the fertilized eggs. In the fertilized egg floating place with a hook raccoon broodstock to remove the broodstock, and remove the fertilized eggs.
The second is to prevent bird and rat damage. During the crab-fishing season, when the water depth is shallow, a large number of migratory birds (including white cranes, grey cranes, black ducks, etc.) fly, causing great harm to the crabs in the lake. These birds are also national protected animals and cannot be harmed. . Therefore, after the migratory birds have entered the lake, they will be driven off by continuing to set off firecrackers. Rats can directly eat crabs that have landed on the shore. Rats are given rodenticides or rodent control devices to eradicate rats where they are often found.
Nine, the harvest entered October, when the crab matured and began to carry out reproductive migration, this time began to crab harvest. Low-lake fishing crabs are caught in cages. Each cage is generally 15m long and 40cm40cm wide. The mature crabs generally flow down the water and concentrate in large numbers at the outlet. Taking into account the actual situation of large catches and difficult to sell, only a few cages are placed at the outlet when crabs are newly hatched. Generally, 1,000 to 1,500 kg of crabs are caught every day. When the crab production is low at the end of the harvest, it starts to drain, stimulating crabs to crawl in the direction of running water. At this time, we must put more cages on the ground. Generally, we should hold an average of every 10 mu. When the water depth is 0.1m, we will not drain any more, so as to prevent crabs from being injured when fishing. In this way, the crabs in the lake can be caught in a month or so.
I. Selection of Hutian Low Hutian is a farmland formed by farmland around the lake in the “grain-based†era, and its low-lying terrain makes it easy to form water. Therefore, the following points must be taken into consideration when selecting low lake fields for crab cultivation: First, there must be plenty of water, good water quality, no pollution, easy access to water and drainage, and drought, irrigation, and drainage. Second, the bottoms of low lake fields should be hard sandy. Soil; Third, the dike is strong, not easy to be storms across, embankment can be more than 2m water conservation; Fourth, to facilitate the transportation, vehicles, boats can be directly to the farming Hutian; Fifth, there is sufficient power for timely access, drainage.
2. Anti-escaping Polyethylene nets are embedded in the dike around the lake. The net height is about 50cm. A 30cm wide hard plastic film is sewn on the upper part of the net; cone-shaped anti-escape nets are installed at the inlet and outlet valves. Near the inlet and outlet, set 2 to 3 blocks on the inside to prevent crabs from fleeing.
3. Qinghu Lake Due to the accumulation of water all year round in the low lake fields, there are a large number of wild black locusts, stingrays and yellow locusts in the lake fields. They must be cleared of lakes before they are released to remove these harmful Fish. The specific measures are: pump the stagnant water in the lake to the lowest water level, use electric catching method to kill the fish as much as possible, and then use 100 ml of “clean pond net†every 6 mu to kill the fish once.
Fourth, to create a suitable ecological environment According to the living characteristics of river crabs in natural lakes, namely: crabs like to live in waters with fresh water, high transparency, rich dissolved oxygen, underlying grasses and a large number of benthos and water depth of about 2m. Low Lake Tanaka artificially creates a suitable ecological environment for his life and promotes the rapid growth of crabs.
1. Cultivate and transplant high-quality aquatic plants to remove harmful aquatic plants.
The quality of aquatic plants is not only a good food for crabs, but also a place for crabs to inhabit, avoid their enemies, and clam shells. It can also improve water quality and increase dissolved oxygen in water. It can also play a role in cooling summers and promoting the growth of crabs. To raise crabs in low lake fields, it is necessary to cultivate high-quality wild aquatic plants and also to transplant high-quality aquatic plants.
Natural lowland Tianzhong itself grows some high-quality wild aquatic plants such as goldfish algae, Hydrilla verticillata, Malay-eyed vegetables, â– grass (oil strips), philodendron (water peanuts), and pristine grasses. These plants are lakes The main water plants, which account for 80% of the total amount of aquatic weeds, should guarantee the growth and reproduction of these plants.
While ensuring the rapid growth of wild aquatic plants in the lake, it is also necessary to transplant some high quality aquatic plants like crabs. One is planting Vallisneria using the method of seeding. Vallisneria, also known as noodles, duck tongue grass, and leek grass, is a typical submerged plant. It is one of the aquatic plants that the crabs like to eat. The seeds are small, the seeds are wrapped in the grass clips, and soaked in water for 10 to 15 minutes before sowing. Then, the grass seed is pulled out with a sampan, and the soil and grass seeds are mixed well and then sowing can be performed. Each kilogram of grass seeds can be sown with 5 to 8 acres. The second is the use of sowing method for the transplanting of goldfish and black-green algae, that is, from the rivers and large lakes to take gold algae or black algae, and then cut it into small pieces of about 15cm, and then spread it into the lake, per acre Grass 10kg to 15kg.
In the crab breeding process, the growth height of aquatic weeds should be controlled to avoid growing out of the water surface. If water grows out of the lake, it will directly affect the light in the lake and the exchange of water in the upper and lower layers, resulting in a decrease in water temperature and a decrease in dissolved oxygen, which is not conducive to normality of crabs. Grow. Therefore, always keep the height of the water below 30cm above the water surface. If you exceed this height, you must cut off the height. While transplanting high quality aquatic weeds, we remove harmful water plants such as water chestnuts, water chestnuts, and lotus leaf that affect light and water quality in lake fields.
2. Transplant snails.
Snails are a type of shellfish and live food for crabs. Living snails can not only ingest benthic algae and organic debris in the bottom of the lake, but also improve water quality. After the snails are released, some snails that have not been ingested can also reproduce, increase the number of live baits, and have multiple functions. From March to June, it is the season of snail breeding, and its body harbors a lot of young snails. At this time, transplanting snails is not only conducive to the breeding of snails, but also meets the needs of juvenile snails and crabs to take up juvenile snails. When transplanting, put snail 200-300kg per acre is appropriate.
Fifth, seed selection and delivery
1. Seed selection.
At present, China has formed a large-scale production of crab crabs mainly Liao crab and Yangtze crab, followed by Minjiang crab and Yellow River Crab. Because these crabs grow in different water systems for a long time, the natural environment is quite different. Therefore, the growth rules of crabs in different river systems have their own characteristics. The crab grows fast, has a short life cycle, matures early, comes into the market early, and concentrates on fishing (this also applies to farming in the South). The Yangtze River Crab also grows fast, but has a long life cycle, is late in its maturity, and is listed late for fishing. In order to increase economic efficiency, it is easy to decentralise the market and raise the selling price. Most crabs are selected as breeding objects when raising crabs in low lake fields. When selecting the Yangtze River crab, generally grasp the following principles: (1) fast growth, large specifications. (2) No disease, no residue, and strong physique. (3) crawling against water faster.
2. Stage seedlings.
The seedlings are planted in stages. The "round catch and release" is a set of effective crab cultivation methods that we have concluded during the crab cultivation in low lake fields. After the lake fields have been cultivated in mid-April each year, when the water temperature exceeds 18°C, they are released. When the Yangtze River crabs were bred early in the year, the specifications were generally around 10,000/kg, and 400 to 500 animals were released per mu. Because the individual crabs are small and easy to be attacked by predators, after the crabs are transported, they must first be put into the lake and surrounded by polyethylene nets to be raised in the holding area. The density of the crabs is 20,000 or so per mu. Feed the cooked, small-sized fish in a timely manner and feed it at 20% of the body weight of the crabs. When the crabs grow to 1000/kg, the fence is removed and the crabs spread to the entire lake. In early July, conventional Yangtze River crabs will be released again. The specifications will be 8,000 birds per kg, and 400 to 500 animals per acre will be thrown directly into the lake to cultivate large-sized crab species and no longer reared. When crabs are caught in the fall, the seeds are left in the lake. Using this breeding method, a batch of commercial crabs can be harvested in the same year, and a batch of large-sized crab species can also be cultivated. Such crab species have strong adaptability to the environment and high survival rate, and can produce large-size commercial crabs in the following year.
Six, water quality control
1. Control the water depth and adjust the water temperature.
In the process of crab cultivation, different water depths are controlled at different growth stages to facilitate the normal development and growth of crabs. In spring, the temperature is low, the water depth is controlled to 0.5m, and sunlight can directly reach the bottom of the lake. The water temperature rises quickly, which is beneficial to the growth of aquatic plants and the recovery of river crabs. We know that the suitable growth temperature for crabs is 15°C to 30°C, and the optimum growth temperature is 25°C to 28°C. When the water temperature is above 33°C, it stops feeding and is in a semi-conscious state. Therefore, when summer arrives and the temperature and water temperature are high, water injection into the lake is started so that the water depth gradually reaches about 2m. In this way, even in the hot summer months when the surface water temperature is 35°C, the bottom water temperature of the lake can still be maintained at about 28°C, thus ensuring the normal feeding and growth of crabs. In autumn, the water depth in the lake remains about 2.0m. This water temperature is constant, and it is not susceptible to cold currents and cooling. It can ensure that the crab has a water environment for smooth growth and fattening. In winter, crabs and fish are netted and immediately added to 0.5m to 0.7m to facilitate safe wintering.
2. Lime splashes regulate water quality.
In the process of raising crabs, during the high-temperature season from June to August, the lime is sprinkled into the lake once every 20 days. Each time, 6 kg per acre is spilled. Lime and lime can improve water quality and increase the transparency of water. Secondly, it can increase the concentration of calcium ions, and facilitate the absorption of crabs and clam shells. Thirdly, it can increase the pH of water bodies (because the water in the lake fields is acidic), and it has many effects.
3. Increase the volume of water exchange.
After entering the summer, water is first injected into the lake, and drainage begins when the water depth reaches 2m. By adopting the “edge-to-edge†approach, the entire body of water in the lake will become alive, basically forming a pattern of running water and raising crabs. This will not only be beneficial to the growth of crabs and increase the total output, but will also reduce the occurrence of diseases in the breeding process.
7. The feeding of bait feed should follow the principle of “pre-rough, medium-green, and later-fineâ€. The previous period (before May) was the initial release and recovery period of crabs. The bait was mainly used to cultivate aquatic plants and put snails. The crabs mainly ingest aquatic plants and tender grasses. Wild fish eggs and flies on leaves and aquatic plants. The mid-term (June-August) is a hot season. At this time, feeding animal feeds tends to spoil the water quality. Therefore, aquatic grasses and transplanted snails are still the dominant species in this period. With the end of the high-temperature season, the water temperature gradually drops to 28°C. Below, the river crab enters the suitable temperature growth period, at this time must mix with feeds some wheat, corn, soybean, broad bean and other plant foods. In the later period, generally after September, the crabs begin to mature their shells for the last time. At the same time, they also enter the fattening and rapid weight gain stages. At this time, they are required to feed some low-value fish and other animal foods while feeding plant foods to strengthen nutrition. To increase crab production and specifications.
VIII. Injury First, catch fish. Although crabs have been sterilized prior to their release, they are sometimes not removed. Therefore, the wild fish in the lake must be further fished after the spring season. According to the habit of yellow sturgeons preferring to inhabit and hunt deeper around the lake, the stingrays are used to remove the stingrays from the lake; according to the behavior of the yellow sturgeon preferring to prey on the watery areas of the lake, it is used in the grass. The method of burying the fish larvae catches the yellow cricket; according to the breeding habits of the quail, the quail eggs are floating on the water for hatching after the pupa are laid, while the brooding fish of the male and female of the black locust ambush under the fertilized eggs to care for the fertilized eggs. In the fertilized egg floating place with a hook raccoon broodstock to remove the broodstock, and remove the fertilized eggs.
The second is to prevent bird and rat damage. During the crab-fishing season, when the water depth is shallow, a large number of migratory birds (including white cranes, grey cranes, black ducks, etc.) fly, causing great harm to the crabs in the lake. These birds are also national protected animals and cannot be harmed. . Therefore, after the migratory birds have entered the lake, they will be driven off by continuing to set off firecrackers. Rats can directly eat crabs that have landed on the shore. Rats are given rodenticides or rodent control devices to eradicate rats where they are often found.
Nine, the harvest entered October, when the crab matured and began to carry out reproductive migration, this time began to crab harvest. Low-lake fishing crabs are caught in cages. Each cage is generally 15m long and 40cm40cm wide. The mature crabs generally flow down the water and concentrate in large numbers at the outlet. Taking into account the actual situation of large catches and difficult to sell, only a few cages are placed at the outlet when crabs are newly hatched. Generally, 1,000 to 1,500 kg of crabs are caught every day. When the crab production is low at the end of the harvest, it starts to drain, stimulating crabs to crawl in the direction of running water. At this time, we must put more cages on the ground. Generally, we should hold an average of every 10 mu. When the water depth is 0.1m, we will not drain any more, so as to prevent crabs from being injured when fishing. In this way, the crabs in the lake can be caught in a month or so.
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