The scientific name of green crab is blue-sawn crab. Because artificial breeding technology has not been completely solved, it cannot be industrialized. At present, the following two methods are mainly used to obtain seedlings:
One is to catch big-eyed larvae and the other is to catch young crabs. Young crabs have a long history of fishing, but there are many deficiencies:
1, Crab seedlings come from different sources. Some sea areas have higher salinity and some sea areas have lower salinity. If they are all stocked in the same pond, the survival rate of crab seedlings will be affected.
2, specifications are not uniform. Crabs caught by trawls and other operations are of varying sizes and they are easily stocked together to form crabs and affect the survival rate of crabs;
3, crab seedling prices are too high. The average price of a juvenile crab is 2-5 yuan, and the cost of seed investment is close to 5-80000 yuan/mu. It is not appropriate to promote breeding in large areas and it is difficult to form large-scale farming;
4. The traditional culture methods are staged, and the crab ponds are idle for a long time, which indirectly increases the cost of breeding;
5. The traditional cultured crabs are listed in two stages and it is difficult to expand sales channels.
Relatively speaking, the crude can make up for the above deficiencies:
1, the cost of breeding is low. The cost of stocking fry is 700-1000 yuan/mu, which greatly reduces the cost of breeding;
2, obvious benefits. Calculated according to the survival rate of 40%, the net income can reach yuan / mu, that is, according to the survival rate of 10%, you can maintain the cost, thereby reducing the risk of investment;
3, short breeding cycle. About 120 days from the seedling to the harvest;
4. Changed the single structure of traditional crab cultivation;
5, can be raised for two years in one year, can provide commodity crabs listed throughout the year, to provide conditions for the expansion of distribution channels;
6. Raise the index of re-education and improve the breeding efficiency of crab ponds;
7. Provide a more effective way for large-scale breeding of blue crabs.
Catch natural bigeye larvae
The crab breeding season in Zhuhai is from March to May and from August to October, and from March to March is the peak period. Captive fishing is performed using a fishing net with a 1-1.5 mm mesh. The captured large-eyed larvae (cub crabs) can be raised in ponds and covered with water grass. Holding time should not be too long. Crabs are generally transported in a foam box. There should be an escape screen around the box.
Large-scale large-eye larvae
1, stocking density
Green crabs can be divided into two groups for one year. The stocking densities can be adjusted according to the breeding season, tide, weather and other conditions. Generally, the amount of seedlings of bigeye larvae is 5000-10000/mu. The seedlings should be released in the morning to avoid the high temperature period.
2, feed feeding
Green crab is omnivorous, big eye larvae mainly through the filtration of organic matter and algae in the water, but also to capture more than their own body of food, so the feed to feed the main slurry, together with the sand plover (red meat blue quail) Live feeding. In the early feeding period, mainly oysters are used as the main slurry, and some fish pastes are fed together. They are fed continuously for 10 days. Each 10,000 big-eyed larvae invest 1 kg of raw oysters and half a catty of fish (calculated on fresh materials), and each They were fed 40-80 kg of sand worms once a day, and plants were placed in the four corners of the pond to increase the survival rate of bigeye larvae.
Big eye larvae are cultivated for about 10 days and the oyster shell becomes young crabs. After juvenile crabs have been shelled for 4-5 times, the higher density should be kept in separate ponds, generally keeping at 2000-3000/mu. The cultivation of young crabs is similar to that of big eye larvae. Feeding volume should be increased. Artificial diets can be fed for 10 days. 40-80 kg sandworms are fed once every 2-3 days. After that, sand and fish can be fed. Until you develop a young crab or crab that meets the specifications.
Normally, feed is fed twice a day and fed at 6 o'clock in the morning. The fed amount accounts for 30%-40% of the total daily feeding amount, and is fed at 5 o'clock in the evening. The fed amount accounts for 60%-70% of the total feeding amount. The feeding amount is 5% -10% of the body weight of the crab. The feeding condition can be observed by placing the quail to determine the increase or decrease of the diet. Conditions such as high temperature, heavy rain, and low salinity should be appropriately cast.
3, water quality monitoring
Because bigeye larvae have weaker activity than juvenile crabs, poor disease resistance and frequent clam shells, large eye larvae (larvae) have relatively high environmental requirements for aquaculture water bodies. The water temperature (water surface and bottom) should be measured twice a day, every day. According to the water temperature, the amount of feed, drainage, or sheltering can be determined. Conditional monitoring of salinity, pH, and transparency is possible from time to time. At the same time, the depth of the water body is generally 1 meter, and the conditional water can be changed every day, no more than 1/2-1/3 at a time, and the juvenile crab can not change the water when it is heavily shelled. Unconditionally changing the pond, as long as the monitoring of good water, or proper splash of probiotics to regulate water quality, you can also change the water. During the cultivation period, the water bodies should be sterilized on a regular basis. Every 20-30 days, 10-15ppm of quicklime can be used for Quanchiposa, or 0.6ppm of bleach can be used for Quanchiposa.
4, daily management
(1) List and register the status of water color, weather, feeding, medication, and crab feeding, growth and disease every day so as to timely summarize and improve the breeding techniques;
(2) The rainy season in Zhuhai is long. Continuous heavy rain will drastically reduce the salinity of water bodies. In addition to discharging the upper water of crab ponds in time, some coarse salts may be sprinkled to relieve the local salinity;
(3) Check whether there is a crab hole in the dam and, if so, plug it in time. At the same time, check if the water quality deteriorates or if the crab is sick;
(4) Observe whether there are dead fish, dead shrimps or dead crabs on the edge of the pond, pay attention to the state and location of the death, and remove and examine the fish in time.
(5) If bubbles appear on the surface of the wind during wind blowing, it means that there is too much organic matter and the water should be changed as soon as possible;
(6) Pay attention to the smell of water. The organic matter in the water body consumes a lot of oxygen at night, or a large amount of toxic substances overflows, causing the death of crabs due to hypoxia or poisoning;
(7) A large number of crabs were found crawling and even refused to launch. This was caused by environmental discomfort and caused severe anoxia, or toxic substances in the pool, or ciliated worms. The cause should be checked;
(8) There is a large amount of chironomid larvae (red worms) or mothheads in the sediment, and the water body is rare, indicating that the ponds have been seriously polluted;
(9) Disinfect regularly with lime, calcium peroxide, zeolite and photosynthetic bacteria.
One is to catch big-eyed larvae and the other is to catch young crabs. Young crabs have a long history of fishing, but there are many deficiencies:
1, Crab seedlings come from different sources. Some sea areas have higher salinity and some sea areas have lower salinity. If they are all stocked in the same pond, the survival rate of crab seedlings will be affected.
2, specifications are not uniform. Crabs caught by trawls and other operations are of varying sizes and they are easily stocked together to form crabs and affect the survival rate of crabs;
3, crab seedling prices are too high. The average price of a juvenile crab is 2-5 yuan, and the cost of seed investment is close to 5-80000 yuan/mu. It is not appropriate to promote breeding in large areas and it is difficult to form large-scale farming;
4. The traditional culture methods are staged, and the crab ponds are idle for a long time, which indirectly increases the cost of breeding;
5. The traditional cultured crabs are listed in two stages and it is difficult to expand sales channels.
Relatively speaking, the crude can make up for the above deficiencies:
1, the cost of breeding is low. The cost of stocking fry is 700-1000 yuan/mu, which greatly reduces the cost of breeding;
2, obvious benefits. Calculated according to the survival rate of 40%, the net income can reach yuan / mu, that is, according to the survival rate of 10%, you can maintain the cost, thereby reducing the risk of investment;
3, short breeding cycle. About 120 days from the seedling to the harvest;
4. Changed the single structure of traditional crab cultivation;
5, can be raised for two years in one year, can provide commodity crabs listed throughout the year, to provide conditions for the expansion of distribution channels;
6. Raise the index of re-education and improve the breeding efficiency of crab ponds;
7. Provide a more effective way for large-scale breeding of blue crabs.
Catch natural bigeye larvae
The crab breeding season in Zhuhai is from March to May and from August to October, and from March to March is the peak period. Captive fishing is performed using a fishing net with a 1-1.5 mm mesh. The captured large-eyed larvae (cub crabs) can be raised in ponds and covered with water grass. Holding time should not be too long. Crabs are generally transported in a foam box. There should be an escape screen around the box.
Large-scale large-eye larvae
1, stocking density
Green crabs can be divided into two groups for one year. The stocking densities can be adjusted according to the breeding season, tide, weather and other conditions. Generally, the amount of seedlings of bigeye larvae is 5000-10000/mu. The seedlings should be released in the morning to avoid the high temperature period.
2, feed feeding
Green crab is omnivorous, big eye larvae mainly through the filtration of organic matter and algae in the water, but also to capture more than their own body of food, so the feed to feed the main slurry, together with the sand plover (red meat blue quail) Live feeding. In the early feeding period, mainly oysters are used as the main slurry, and some fish pastes are fed together. They are fed continuously for 10 days. Each 10,000 big-eyed larvae invest 1 kg of raw oysters and half a catty of fish (calculated on fresh materials), and each They were fed 40-80 kg of sand worms once a day, and plants were placed in the four corners of the pond to increase the survival rate of bigeye larvae.
Big eye larvae are cultivated for about 10 days and the oyster shell becomes young crabs. After juvenile crabs have been shelled for 4-5 times, the higher density should be kept in separate ponds, generally keeping at 2000-3000/mu. The cultivation of young crabs is similar to that of big eye larvae. Feeding volume should be increased. Artificial diets can be fed for 10 days. 40-80 kg sandworms are fed once every 2-3 days. After that, sand and fish can be fed. Until you develop a young crab or crab that meets the specifications.
Normally, feed is fed twice a day and fed at 6 o'clock in the morning. The fed amount accounts for 30%-40% of the total daily feeding amount, and is fed at 5 o'clock in the evening. The fed amount accounts for 60%-70% of the total feeding amount. The feeding amount is 5% -10% of the body weight of the crab. The feeding condition can be observed by placing the quail to determine the increase or decrease of the diet. Conditions such as high temperature, heavy rain, and low salinity should be appropriately cast.
3, water quality monitoring
Because bigeye larvae have weaker activity than juvenile crabs, poor disease resistance and frequent clam shells, large eye larvae (larvae) have relatively high environmental requirements for aquaculture water bodies. The water temperature (water surface and bottom) should be measured twice a day, every day. According to the water temperature, the amount of feed, drainage, or sheltering can be determined. Conditional monitoring of salinity, pH, and transparency is possible from time to time. At the same time, the depth of the water body is generally 1 meter, and the conditional water can be changed every day, no more than 1/2-1/3 at a time, and the juvenile crab can not change the water when it is heavily shelled. Unconditionally changing the pond, as long as the monitoring of good water, or proper splash of probiotics to regulate water quality, you can also change the water. During the cultivation period, the water bodies should be sterilized on a regular basis. Every 20-30 days, 10-15ppm of quicklime can be used for Quanchiposa, or 0.6ppm of bleach can be used for Quanchiposa.
4, daily management
(1) List and register the status of water color, weather, feeding, medication, and crab feeding, growth and disease every day so as to timely summarize and improve the breeding techniques;
(2) The rainy season in Zhuhai is long. Continuous heavy rain will drastically reduce the salinity of water bodies. In addition to discharging the upper water of crab ponds in time, some coarse salts may be sprinkled to relieve the local salinity;
(3) Check whether there is a crab hole in the dam and, if so, plug it in time. At the same time, check if the water quality deteriorates or if the crab is sick;
(4) Observe whether there are dead fish, dead shrimps or dead crabs on the edge of the pond, pay attention to the state and location of the death, and remove and examine the fish in time.
(5) If bubbles appear on the surface of the wind during wind blowing, it means that there is too much organic matter and the water should be changed as soon as possible;
(6) Pay attention to the smell of water. The organic matter in the water body consumes a lot of oxygen at night, or a large amount of toxic substances overflows, causing the death of crabs due to hypoxia or poisoning;
(7) A large number of crabs were found crawling and even refused to launch. This was caused by environmental discomfort and caused severe anoxia, or toxic substances in the pool, or ciliated worms. The cause should be checked;
(8) There is a large amount of chironomid larvae (red worms) or mothheads in the sediment, and the water body is rare, indicating that the ponds have been seriously polluted;
(9) Disinfect regularly with lime, calcium peroxide, zeolite and photosynthetic bacteria.