(1) Cultivation of Eriocheir sinensis
In order to improve the survival of young crabs and increase economic benefits, it is necessary to cultivate crabs first. At present, in order to make the big-eyed larvae reach the commercial crabs, the temporary rearing technology in plastic greenhouses is mostly adopted. Choose good water quality and sufficient water source; Note: The pond with convenient drainage, no water leakage, no water seepage and little silt should not be too large, and the water depth should not exceed1.2m. The east-west direction of the pond is better, and there is plenty of sunshine. For greenhouse construction, please refer to the construction method of agricultural vegetable greenhouse.
Before releasing crab seedlings/0/5-20 days in Kloc-0, 75 kilograms of quicklime should be sprinkled and disinfected per mu. After the medicinal properties disappear, water should be fed through a 80-mesh filter to cultivate basic bait, transplant aquatic plants (which must be strictly disinfected) and set up necessary escape prevention facilities. Crab seedlings can be shallower when entering the pool. Conducive to improving the water temperature and the growth of algae and aquatic plants in the water. Feed the bait 2-3 times a day, such as soybean milk, fish, shrimp paste, etc., and feed more in the surrounding shallow areas, and feed at 4% of the body weight, and always pay attention to the weather, water sanctions, individual growth, and the number of organisms competing for bait. With the growth of young crabs, we should also add some plant bait, such as duckweed and other high-quality aquatic plants. In daily management, we should pay attention to water quality regulation, master the water quality to be fat and cool, and change the water frequently and less, so as not to cause drastic changes in water temperature and water level. After about 2 months of cultivation, the crab can be detained.
(2) Adult crab culture
Adult crabs like the water environment with clean water and great transparency, with abundant aquatic plants and rich bait, which is the most suitable for the growth of river crabs. At present, most of them are cultured in ponds, lakes, rivers and rice fields. Now give priority to with the pond for a brief introduction:
1, pond conditions
Adequate water source, convenient water intake and drainage, good water pollution, clay, sandy soil or sub-sandy soil with good ventilation, which is beneficial to the growth and reproduction of aquatic plants, benthic insects, snails, water worms, etc. The old pond should be thoroughly dredged, and the silt should not exceed 20cm, and the pond area should not be too small. The water depth of the pond is kept at about 0.6-1.5 meters all the year round, and the water depth varies from place to place. At the shallowest point, 10cm, several mounds slightly above the water surface can be built in the pond, that is, crab island, where aquatic plants can be transplanted. The pond should not be too steep, and the slope ratio is generally 1: 1.5. Artificial caves can also be built.
2. Transplanting aquatic plants
The natural yield of Eriocheir sinensis mainly depends on the number of aquatic plants and benthic organisms (bait organisms) in the waters. It is an indispensable technical measure to plant aquatic plants well in the process of breeding. Planting aquatic plants can not only feed crabs and supplement vitamins for ten days, but also support the fighting and concealment, which is a powerful measure to improve the survival rate of river crabs in each period. In addition, it can absorb harmful ammonia nitrogen, carbon dioxide and organic substances in the pool, release oxygen and stabilize water quality. The masses often say that "the size of the crab depends on the water plants". Therefore, it is necessary to make great efforts to plant aquatic plants for river crabs cultured in ponds. The main types of aquatic plants are duckweed, Azolla, water hyacinth, water hyacinth, verticillata verticillata, Ceratophyllum demersum, Sophora alopecuroides, Alternanthera philoxeroides and so on, and attention should be paid to disinfection and prevention when transplanting.
3. Escape prevention facilities
Escape prevention facilities mostly use plastic film, but also useful cement board, depending on their own situation.
4, pond cleaning disinfection
Generally, the pond is disinfected with quicklime half a month before the seedlings are released, and the dosage is 75 kg per mu. On the one hand, it can kill harmful organisms, on the other hand, it can improve the bottom of the pond, increase the content of calcium ions in the water, and promote the growth of Eriocheir sinensis molting. Fertilize in time after receiving water, cultivate algae and basic bait, and the transparency should generally be kept at 40-50 cm. If tadpoles or frog eggs are found, they should be removed in time to avoid competing for food and harming young crabs.
5, put the seedlings
The crab seedlings produced in the Yangtze River system are the best for seed selection, requiring neat specifications, complete steps, strong physique, active crawling and no injury or disease.
Seeding and density, pay attention to the temperature difference when seeding. The fry bought from other places cannot be directly put into the pond, so they should be soaked in water for 2-3 minutes, taken out and put into the pond for 10 minutes, and repeated for 2-3 times. After the young crabs gradually absorb enough water and adapt to the water temperature, they can be put into the pond, which can improve the survival rate.
Density: At present, most of them are polyculture, especially fish, shrimp and crab polyculture, which will bring higher economic benefits. The density can be controlled within 1500 crabs/mu, and the specification is120-150 crabs /kg. If the conditions are poor or shrimp farming is the main thing, the amount of seedlings released can be reduced appropriately.
6. Daily management
(1) Feeding: The whole process of intensive culture in ponds mainly depends on artificial feeding, so the types, advantages and disadvantages of feed have a great influence on the growth and development of river crabs. When feeding, we should adhere to the principle of reasonable collocation of fine, green and coarse, with animal concentrate accounting for 40%, aquatic plants accounting for 35%, other plant feed accounting for 25%, and there are three main types of feed (. (2) Animals: small miscellaneous fish in sea and fresh water, dead bodies of various animals, snails, mussels, blood of livestock and poultry, fish meal, silkworm chrysalis, etc.; (3) Botany: aquatic plants, duckweed, Alternanthera philoxeroides, black algae, etc., and commercial feeds: sweet potato, Ma Ling potato, cereal, bran, fodder bran, etc.
As in pond culture, the feeding method of river crabs is "four observations and four determinations", that is, watching seasons, weather, water quality and crab activities, timing, fixed point, qualitative and quantitative.
Depending on the season: young crabs should be fed with some live animal feed in spring, and the amount of animal feed should be appropriately increased in the middle growth period of river crabs, especially in May-August. However, plant feed is the main feed, and in the later period, river crabs need a lot of nutrition to meet the gonad development, so they should be fed with more animal feed, so that the weight of river crabs will increase and the meat taste will be delicious. The feed distribution is generally 40% from March to June, 7-/kl.
Look at the weather: feed more when it is sunny, less when it is rainy, stop feeding when it is sultry and windy before the shower, and feed when it is foggy.
Look at the water quality: the water quality is clear, the bait can be fed normally, the water quality is strong, the feeding should be reduced appropriately, and the water should be changed in time.
Look at the activity of crabs: generally, they are eaten up the next morning after feeding, and the feeding amount is appropriate, which indicates that the crab has a poor appetite or an excessive number. Therefore, the reasons should be analyzed in time to reduce the feeding amount, and the feeding amount should be appropriately increased during the molting period.
Timing: Eriocheir sinensis has the habit of staying up at night and going out for food at night. Feeding is carried out at 8: 00 am and 9: 00 am and in the afternoon and evening, and the feeding amount in the evening is 60-70% of the feeding amount all day.
Fixed point: the feed to be fed should have fixed food, and the feed should be scattered on the feed table or on the slope near the shallow water level, so as to observe the feeding and activities of river crabs and increase or decrease the feed at any time. Eriocheir sinensis has a strong competition for food, so it is necessary to set up more points to make Eriocheir sinensis eat evenly and avoid killing each other because some of them are all small or weak and can't compete for feed.
Qualitative determination: Eriocheir sinensis is sensitive to fragrant, sweet, bitter, salty, smelly and other tastes, and the feed it feeds must be fresh and palatable and rich in protein.
Quantification: "If you don't eat fish for a day, it will last for three days", so does the river crab. This requires that the feeding amount should be determined according to the size, density, different seasons, weather and activities of the river crab. Generally, the daily feeding amount is 8-10% of the body weight of the crab in the pond. If the feeding amount is small, it can only maintain life, and if it exceeds the timely range, it will also affect growth and increase the feed coefficient.
When feeding bait, animal and plant feeds should be matched, such as forage and grain in the morning and mussels, snails and silkworm chrysalis in the afternoon. Avoid feeding a single feed for a long time, otherwise it will cause anorexia, low feed utilization rate, affect growth and small specifications.
(2) Water quality management: Eriocheir sinensis has higher requirements for water quality than fish, and is more sensitive to polluted water. The water quality in the pond is good, which is beneficial to the growth and development of Eriocheir sinensis, and the meat tastes delicious. The PH value of the crab pond water should be kept at 7-9, with an optimum of 7.5-8.5, and the dissolved oxygen in the pond should be kept above 5MG/ 1 and below 5 mg//kloc-. The crab will die when it is below 2MG/ 1. Adjust the PH value of the pond water. At present, the water quality of newly excavated ponds is mostly acidic, so it is necessary to sprinkle quicklime slurry regularly to improve the water quality, which can improve the utilization rate of feed for river crabs and help them shed their shells smoothly. Generally, it is once a month in spring and once every 1 5-20 days in summer and autumn, with the water depth per mu.
Pay attention to changing the water frequently to keep the water level stable. Change the water once a week in spring and once every three days in summer. In case of continuous high temperature, change the water every day. It is hot in autumn, and muggy weather often occurs, so the water quality is easy to deteriorate. Pay special attention to changing the water, and change it every two days, and the water exchange volume accounts for13 of the whole water area.
Eriocheir sinensis is not tolerant to fat water. In order to control the water quality from becoming fat, 200-300 fish species of silver carp are put in each mu and an aquatic plant is planted around the crab pond.
The requirements for water level in crab ponds are different in different seasons. In order to raise the water temperature and promote the growth of river crabs in spring, the water level can be controlled at 0.5—0.7m, and the water temperature is higher in summer and autumn, and the depth of the pond water should be kept at1-1.5m..
(3) Escape prevention: Special personnel are on duty to patrol the dike, especially when it rains and changes.
(4) Patrol the pond: observe the color of the water, pay attention to the activities of crabs, do not hurt the crabs, and keep the water environment stable. When the gonads are well developed and the price is suitable, the pool water can be drained and picked up.
Third, disease control
1, rot disease
The tip of the diseased crab's foot was damaged, and it became a black ulcer and rotted, and then white spots appeared on each foot joint, back nail and chest plate, and gradually became a black ulcer. In severe cases, the carapace was eroded into holes, and muscles or skin membranes were visible, which led to the death of the crab. The disease was caused by the damage of the tip of the crab's foot and the infection of bacteria.
Prevention methods:
(1) Clean the pond thoroughly with quicklime to keep the water clean, and add fresh water frequently in summer to keep 5-10cm silt at the bottom of the pond.
(2) In the pond with signs of illness, the whole pond is splashed with quicklime mixed with water15-20 ppm.
Treatment: Spray it all over the pool with 2PPM bleaching, and add sulfanilamide drugs to the feed, adding 0.1-0.2g per kilogram of feed for 3-5 days.
2. Black gill disease
The diseased crab's gills are discolored by infection. When it is light, the left and right gills are dark gray or black, and when it is heavy, all the gills turn black. The diseased crab is slow to move and has difficulty breathing, commonly known as sighing disease. This disease mostly occurs in the late stage of adult crab culture, and the deterioration of water environment conditions is the main cause of the disease. Prevention of the same rot disease.
3, rotten limb disease
The abdomen and appendages of sick crabs rot. During the wintering period, the incidence of this disease is high, and the appendages appear spotted rot, and the spots turn from yellow to gray to black. This disease is caused by injuries during the process of fishing, transportation and stocking, or injuries caused by enemies during the growth process.
Prevention methods:
(1) Don't hurt the crab in the process of fishing, transportation and stocking.
(2) Before stocking, put the river crab in 2PPM furazolidone solution for several minutes and then put it in.
Treatment:
(1) oxytetracycline or furacilin spilled in the whole pool was 0.5— 1PPM.
(2) Furazolidone spilled in the whole pool was 0.1-0.2 ppm.
(3) The quicklime is splashed in the whole pond in the form of15-20 ppm, and applied for 2-3 times continuously.
4. Edema: The abdomen, navel and the lower part of the back shell of the sick crab are swollen, and the sick crab crawls by the pool, refuses to eat, and finally dies in the shallow water near the pool. This disease is caused by the abdominal injury and infection of the river crab during the cultivation process.
Preventive measures: In the process of breeding, especially when molting, try to reduce the disturbance to the river crab and avoid its injury.
Treatment:
(1) oxytetracycline or furacilin spilled in the whole pool was 0.5— 1PPM.
(2) Furazolidone was sprayed in the whole pond by 0.1-0.2 ppm.
5. Water mold
The diseased crab's body surface, especially the flocculent silk growing on the wound, moves slowly, eats less, and the wound does not heal, which leads to the ulceration and spread of the wound tissue, resulting in death. The disease is caused by the injury of the river crab and the invasion of mold into the wound.
Prevention methods:
(1) Don't hurt the crab in the process of fishing, transportation and stocking.
(2) A large number of animal feeds were added before molting.
Treatment:
(1) malachite green is 0.25PPM in the whole pool, and applied once after 5 days.
(2) Soak the sick crab with 3-5% salt solution for 5 minutes, and smear the affected area with 5% phosphorus.
6, ciliary disease
Ciliated protozoa can be attached to the joints, feet, back shell, forehead, appendages and gills of sick crabs. There are more dirt on the body surface of sick crabs, and their activity and feeding ability are weakened. In severe cases, they can die before dawn. The disease is caused by over-fertilization of pool water, long-term non-replacement, and excessive ciliate reproduction.
Prevention method: change the pool water frequently to keep the water fresh.
Treatment:
(1) Sprinkle 5-10ppm with 30% aldehyde.
(2) Sprinkle 0.7PPM with copper sulfate and ferrous sulfate (5:2) in the whole pool.
(3) Soak the sick crabs with the mixed solution of 0.5-1ppm bromogeramine and 5-10ppm potassium permanganate.
(4) Use 0.2-0.3 ppm malachite green to splash along the crowded places of river crabs such as aquatic plants beside the pool.
7. Crab slave disease
The abdomen of the sick crab is slightly bloated. When the umbilical cover is opened, it can be seen that the milky white or translucent granular worms with a thickness of about 1 mm are parasitic on the accessory branches or chest plates. The sick crab grows slowly, the gonads are poor, and the river crab seriously parasitized by crab slaves has a foul smell and is inedible. The main reasons for this disease are the high salt content in the pool water, the massive reproduction of crab slaves and the spread infection of larvae.
preventive
(1) Clean the pond thoroughly and kill the crab slave larvae in the pond. Common drugs include bleaching powder, trichlorfon and formaldehyde.
(2) Mixed culture of a certain amount of carp in crab ponds can inhibit the number of crab slave larvae.
(3) In ponds with signs of disease, the development and spread of crab slaves can be suppressed by completely replacing the pond water, injecting fresh water (salinity less than 1‰) or moving sick crabs infected with crab slaves to fresh water.
therapeutic method
(1) soak the disease with 5PPM copper sulfate solution10-20 minutes.
(2) Soak the sick crab10-20 minutes with 20PPM potassium permanganate solution.
(3) 0.7PPM of copper sulfate and ferrous sulfate (5∶2) spilled in the whole pool.
8, molting incomplete disease
A crack appeared at the junction of the head, chest and abdomen of the sick crab, but the old shell could not be shed, and the sick crab became black all over and finally died. The common disease of crab culture in ponds is related to the lack of some mineral elements in the growth process.
9. Polyconchocerciasis
Generally, there are many parasites in the crab seedling stage. When there are a lot of parasites, the crab seedlings can't shed their skin and die. When there are many parasites in the gill of young crabs and adult crabs, they can also cause death.
Control method: soak the crab body with 10PPM malachite green for 45 minutes, or soak the crab body with IPPM bromogeramine solution until the collembola falls off.