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River crab breeding technology

⒈Pond selection

①Water source and water quality

The pond should be located close to a water source, with sufficient water supply, no pollution from chemical plants nearby, and good water quality that meets the national fishery water quality standards GBll607-1989.

②Pond conditions

The pond area should be 10-50 mu, and the pond shape should be an east-west rectangle. The water depth should be 0.5-1.5m all year round. The drainage and irrigation facilities should be complete, and the drainage and irrigation should be separated. ③ Anti-escape equipment: Strong and reliable anti-escape equipment should be installed around the pond. Generally, anti-escape equipment includes cement walls, calcium plastic plates, iron sheets, nylon films, fiberglass, etc.

⒉ Preparation before stocking seedlings

①Pond cleaning and disinfection should be carried out 10-15 days before stocking crabs. Common pond cleaning and disinfection drugs include quicklime, bleaching powder, tea dregs, etc. The dosage is determined by the water depth and the amount of silt. For example, quicklime, dry pond cleaning, the dosage per mu is 60-75K, and it is sprinkled all over the pond after dissolving. Quicklime pond cleaning can not only kill harmful organisms in the water, but also improve the soil quality of the pond bottom and increase the calcium content in the water, which plays an important role in the growth and development of river crabs.

② Planting aquatic plants

Aquatic plants are not only a place for river crabs to live and hide in their shells, but also have the function of purifying water quality. At the same time, they are also good feed that river crabs like to eat. Common aquatic plants include Hydrilla verticillata, Elodea, and Vallisneria. The coverage area of ​​aquatic plants can reach 60-70% of the pond. Excessive aquatic plants should be removed, and water peanut belts should be set up after the crabs are released.

③Transplanting snails

The meat of live snails is delicious and river crabs love to eat it. It is an ideal high-quality natural feed. It is usually transplanted before the Qingming Festival, with 200-250kg transplanted per acre of water surface.

⒊ Seedlings stocking

The stocking time and quantity are determined according to the size and source of the crab species. For example, if the stocking of 100-200 crabs/kg is carried out, 500-800 crabs are released per mu; if the stocking of 2000 crabs/kg is carried out, 2000-3000 crabs are released per mu. In order to consume the plankton in the water and purify the water quality, silver carp and bighead carp with a size of 50-100g/tail can be stocked at the same time, and about 50 fish can be released per mu.

4. Feeding

River crabs are omnivores. Common plant feeds include various aquatic plants, wheat, corn, rice, bean cakes, bran, etc.; animal feeds include benthic animals such as snails, clams, and mussels, slaughterhouse scraps, fish and shrimp, blood meal, silkworm pupae, maggots, earthworms, and cladocerans and copepods; in addition to natural and artificial single baits, there are also full-price compound baits. The feeding of bait should adhere to the four principles of "timing, positioning, quality, and quantity". Timing means feeding once in the morning and afternoon every day, mainly at 5-6 pm; positioning means combining fixed-point feeding with appropriate scattering to ensure that all crabs can eat feed; quality means that the bait is fresh and not deteriorated, and meat, fine, and green feed are reasonably matched; quantity means that the amount of feed is flexibly controlled according to the growth stage, season, weather and other factors to ensure that the crabs eat enough and eat well, and avoid being full or hungry.

5. Water quality control

The water level of the crab pond adheres to the principle of "shallow in front, deep in the middle, and logistics in the back", that is, keep the water level shallow in the early stage to increase the water temperature and promote molting; keep the water level deep in the middle stage, especially in the hot summer and autumn, and always keep the water fresh and sufficient dissolved oxygen. When the water level is too shallow due to natural erosion, add water in time; when the water quality is too concentrated, replace it with new water in time, especially in summer and autumn. When changing water, the water intake speed should not be too fast or too fast. The method of drainage and irrigation can be adopted to keep the water level relatively stable. The number of water changes is to change the water once a week before June, and the water change volume is 1/5-1/4. In July and August, change the water 2-3 times a week, and change the water 1/3 each time. After September, change the water once every 5-10 days, and change the water 1/3-1/2 each time. The new water injected should prevent excessive temperature difference and external pollution.

⒍Replenishing grass and throwing snails

Water plants are not only delicious feed for river crabs, but also the attachment of river crabs in the water; snails are rich in nutrients and contain calcium, phosphorus and other substances necessary for the development of river crabs; water plants and snails can absorb fertilizers in water and soil, which helps to improve the bottom and water quality. In addition to sowing Vallisneria, transplanting water peanuts, duckweed and other water plants before and after the crabs are released, and releasing live snails to reproduce and grow in the crab pond, water plants and snails must be continuously supplemented during the breeding period to ensure that the coverage of water plants accounts for about 60% of the total area of ​​the pond, and the number of snails reaches more than 1,000 per m2.

⒎Daily Management

It is necessary to inspect the pond once in the morning and once in the evening. First, check the water quality. If any changes are found, take measures to add or change water in time. Second, check the feeding situation of river crabs and adjust the amount of bait fed. Third, check the amount of aquatic plants and natural bait. If aquatic plants and snails in the temporary pond are eaten by crabs, they should be replenished in time. Fourth, check the integrity of the escape prevention facilities, especially in windy and rainy weather, and check them at any time to prevent river crabs from escaping. Fifth, check for pests and diseases and invasion by enemies. If any abnormal situation is found, take timely measures to prevent it.

The breeding technology of hairy crab

Many people have eaten hairy crabs, but I believe that there are certainly not many people who understand the hairy crab breeding techniques. Below is the relevant content about hairy crab breeding techniques that I have compiled for you, I hope it can help you.

The technology of breeding hairy crab

Daily Management

Adhere to the sustainable and healthy breeding model and strengthen the quality inspection of the water environment. Through the ecological breeding of reeds, the wetland vegetation is protected, so that the breeding environment in the area has a strong water quality control and purification function, so as to achieve the healthy breeding of river crabs in the Yellow River Estuary. The second is to strengthen the quality inspection and management of the water environment. Through regular or irregular sampling and testing of the reed wetland breeding area, timely grasp the various physical and chemical indicators of the water environment in the breeding area, and reasonably regulate and control it so that the breeding water meets the environmental requirements of river crab breeding and production in the Yellow River Estuary. After the crab seedlings are released, patrol the pond once every morning and evening to observe the growth and feeding of the crabs, regularly test the water quality in the breeding area, and deal with problems in time. Salinity: 0‰~30‰, suitable temperature 15℃~30℃, optimal temperature 22℃~25℃, dissolved oxygen above 5 mg/L, pH value 7.5~8.5, ammonia nitrogen below 0.1 mg/L, hydrogen sulfide below 0.01 mg/L.

Water quality regulation

No drugs are used during the breeding process, and water is basically not changed. When the water quality deteriorates or it rains heavily, water should be adjusted or added in time. The amount of water changed depends on the situation. In production, we strictly follow the pollution-free control technology, do not use pesticides and hormones, etc., and directly use the Yellow River water for natural breeding. In the high temperature in summer, depending on the water quality, water is changed irregularly. The water depth of each water change is 10 cm to 20 cm, and it is drained first and then filled.

Capture and sale

From September to October every year, hairy crabs are caught using light trapping or by inserting nets into various canals. The captured adult crabs should be temporarily kept in net cages for more than 2 hours. After the mud and dirt are spit out and filtered, they are packaged in bags and transported to the market for sale insulated.

Scientific breeding of hairy crabs

1. Prepare for seedling planting and strengthen escape prevention facilities

Use a net to block the crabs to prevent them from escaping. There should be no tall crops around the crab pond. It is best to make the anti-escape wall in an arc shape. When sterilizing and disinfecting the pond, remove excess silt, leaving only about 10 cm of silt, and sprinkle the entire pond with quicklime, using 200-250 kg per mu, to achieve the purpose of thorough pond disinfection, removing weeds and wild animals, killing pathogens, and improving the bottom quality. Seven days after the drug is applied, rinse the pond once to remove dirt, then dry the pond for 3-5 days and then add water.

2. Plant good aquatic plants

To breed hairy crabs, the first thing to do is to plant aquatic plants. The saying "the size of the crab depends on the aquatic plants" shows that aquatic plants are an important factor affecting the size and yield of hairy crabs. In the high temperature period of summer, aquatic plants can not only provide habitats, shelters, molting places and plant bait for Yangcheng Lake hairy crabs, but also play a role in shading, lowering water temperature and improving water quality. The aquatic plants planted are preferably water hyacinth, waterweed, and Vallisneria, which hairy crabs like to eat. The area should account for 1/3-1/2 of the crab pond. Aquatic plants are one of the natural baits for hairy crabs and can play a good role in purifying water quality. You can also put in an appropriate amount of snails.

3. Maintain good water quality

Water environment is the first limiting factor in hairy crab farming, and the quality of water is directly related to the benefits of farming. In the process of hairy crab farming, the water quality should be kept fresh, and it is best to cultivate crabs in micro-flow water where conditions permit. Water bodies with high organic matter content are prone to hypoxia, and a large amount of moss will be produced in the pond, affecting the growth of hairy crabs. In summer, superphosphate (2-3ppm) and quicklime (10-15ppm) should be sprinkled every 15-20 days to adjust the pH value of the water body, supplement calcium for hairy crabs, and promote the growth of crabs (note that the application time of the two should be 3-5 days apart). In addition, it is best to change the water once every 3-5 days during the high temperature period, and the amount of water changed should not exceed 1/3 of the original pool water, and the water level should be maintained at 1-1.5m, and the transparency should be controlled at 35-40cm. Due to the large temperature difference between day and night in autumn, the water quality is prone to deterioration, and the water should be changed frequently in early autumn. As the water temperature drops, the number of water changes should be gradually reduced. It is best to maintain the transparency at around 45cm and the water level at around 1-1.5cm to ensure that the water temperature is relatively stable to facilitate wintering.

4. Reasonable stocking

Before releasing the crabs, the crab seedlings must be disinfected and evenly separated according to size. When releasing the crabs, they must be released into the waters with a seine net. The seine net can only be removed after the crabs have adapted to the environment for one month. Generally, the principle of "three suitability" and "one temporary raising" should be followed in the stocking of crabs. That is, appropriate density, stocking at the right time, moderate specifications, and temporary raising before stocking. The water should not be too deep when stocking, preferably 1.5-2 meters; the temperature is most suitable at 20-25 degrees.

5. Stocking density

In an environment with lush aquatic plants and fresh water, the general specification is about 300 crabs per mu, so that the hairy crabs have sufficient living and growth space. The best time to stock crabs is generally from the end of February to March each year. If the stocking is too early, the wintering casualties will be heavy. If it is too late, the water temperature will rise and some crabs will shed their shells, which will affect the survival rate of the crabs.

6. Scientific baiting

Summer is the peak season for Yangcheng Lake hairy crabs. It is necessary to seize the opportunity to feed them enough and good bait to ensure their rapid growth. At this stage, the proportion of plant bait (such as bean cake, wheat, pumpkin, etc.) should be appropriately increased to help Yangcheng Lake hairy crabs accumulate physical energy and prevent precocious puberty. Autumn is the fattening season for Yangcheng Lake hairy crabs. High-protein baits such as snails, clams, animal scraps and miscellaneous fish should be appropriately increased. Feed twice a day, and the daily feeding amount accounts for 5%-8% of the body weight of Yangcheng Lake hairy crabs. The feeding time is preferably 8:00-10:00 and 17:00-18:00. The feeding amount in the evening accounts for 70% of the whole day. The feeding amount each time should be slightly left over from the last time. The specific feeding amount should be flexibly controlled according to the weather, water quality, and the feeding of Yangcheng Lake hairy crabs. Yangcheng Lake hairy crabs are rampant all over the world.

Disease prevention and control of hairy crabs

Summer and autumn are the peak seasons for crab diseases. Improper management can easily lead to large-scale diseases. Regularly use a combination of oral and external use to prevent crab diseases. External drugs include Jia Ke Jing Xie An; internal drugs include Ban Lan Gen and dehulling. In summer, the water temperature is high, the water quality is easy to deteriorate, and the crab body has weak disease resistance. It is best to sprinkle quicklime once every half a month; bleaching powder, Xie Ning, etc. should be sprinkled throughout the pond irregularly at ordinary times; at this stage, it is best to mix antibiotics and other baits for feeding 3-4 times a month, and adjust the water quality by changing water and splashing lime. After the beginning of autumn, the focus should be on the prevention and control of the "shaking disease" of hairy crabs. Chlorine dioxide, dichlorodiphenylmethane and other drugs can be used to spray the entire pond, and combined with new drugs for the prevention and control of "shaking disease" such as Virus Killer and Ke Dou Ling, they can be taken orally for one week for prevention and control.