The Culture Technology of River Crab with delicious Meat and High benefit

river crab

River crab is favored by consumers at home and abroad because of its rich nutrition and delicious meat. At present, river crab has become the main aquaculture species in various places, and the river crab aquaculture industry has changed from "big crab culture" in pursuit of yield to big crab culture and ecological crab culture centered on quality and benefit. With the development of river crab breeding industry, river crabs with small specifications and poor quality are becoming more and more unpopular with consumers. Large-size river crab not only sells smoothly, but also has an absolute advantage in price. The market price of large-size river crab is 4 times higher than that of small-size river crab. The specification is more than 150g, 120mur160 yuan / kg, while the specification of 75g or so is only 30Muth40 yuan / kg. But how to cultivate and produce pollution-free large-size river crab is the most concerned issue for breeding producers. The so-called large-size river crab refers to the adult crabs weighing more than 150g "green back, white belly, yellow hair and golden claws". Through the summary of production practice for many years, the ecological culture techniques for cultivating large-scale river crabs are mainly as follows:

First, select improved varieties and control the quality of free-range crabs.

Large-size river crabs must be based on high-quality crab species. Select the self-bred or locally bred long-shouldered river system with strong physique, disease-free and injury-free, neat specifications, sound appendages, shiny and dynamic young Chinese mitten crab as crab species, and avoid using young crabs of unknown sources. this is the most important factor in breeding large crabs and improving the survival rate. Usually, high-quality crab species can be selected from three aspects: to identify crab species in the Yangtze River system from several physiological characteristics, such as appearance, body shape, foot, forehead teeth, and so on; to eliminate precocious "little silly crabs" that have no feeding value. The so-called "small silly crab" refers to the first-year-old young crab of that year, weighing 10-35 g: reaching sexual maturity, growth stagnation, and dying one after another. Select healthy and high-quality crab species from the degree of foot disability, seedling activity, and whether there are cattle worms on the body surface.

Second, plant aquatic plants to create a good ecological environment

As the saying goes, "crab size, look at water plants." Planting aquatic plants in the waters of cultured adult crabs, first, as a natural and high-quality plant feed for crabs; second, to provide a hidden place for river crabs to perch and molt, which is not easy to be found by enemies, and to reduce the mutual killing of aquatic plants. The third is the photosynthesis of aquatic plants, which can increase the amount of dissolved oxygen in water, absorb organic matter in water, prevent water eutrophication, purify water quality, maintain fresh water quality and improve the environment for water culture. Fourth, in the high temperature season, aquatic plants can play a role in shading and cooling, which is beneficial to the growth of river crabs. The varieties of aquatic plants planted should not be single, but should be diversified. It is best to combine submerged plants, water-standing plants and floating plants and distribute them rationally, so as to meet the various needs of river crabs. Submerged plants can be selected as bitter grass, verticillium verticillata, Elosa, etc., aquatic plants such as Reed, Zizania caduciflora, floating plants such as duckweed and so on. The area of aquatic plants planted in crab waters should account for 50%-60% of the water surface area. The peak period of river crab feeding on aquatic plants is from July to August in summer, which should be paid close attention to not only to ensure the feeding and utilization of river crab, but also to have a higher storage capacity. When it is not enough, measures should be taken to replenish the aquatic plants, but do not gain too much, the rotten aquatic plants are easy to cause water quality deterioration and cause river crab disease. There are too many aquatic plants, especially too many single species like Elodea, which can easily cause the bottom water not to flow and cause the bottom water to deteriorate, so the water channel should be dredged in time, which is beneficial to the flow of water into and out of the crab pond and improve the water quality of the crab pond. otherwise, black gills, edema and other diseases are easy to occur.

Third, control the stocking density and pay attention to reasonable mixed culture.

The stocking density of crab species is related to crab species specifications, feeding conditions, market requirements, management level and so on. The two-year breeding model can be adopted, that is, crab seedlings are purchased at the end of May and the beginning of June, and then can be bred into buckle crabs at the end of the year. In the spring of the second year, these buckle crabs are put into the pond, and the standard of crab breeding is usually 100ml / kg. The specification and quality of river crab out of the pond can be improved by stocking 300 Mu per mu of water and adopting proper release. Adult crab ponds dominated by river crabs cannot be mixed with herbivorous fish (grass carp, blunt snout bream, etc.), omnivorous fish (common carp, crucian carp, tilapia, etc.), carnivorous fish (snakehead, catfish, sea bass, etc.), but only some filter-feeding negative species (silver carp, bighead carp, etc.). Its purpose is to remove plankton from the water and prevent the water quality from getting worse. However, because there are many water plants and thin water in the river crab pond, the number of mixed culture should not be large. Generally, 50-100g/ silver carp and bighead carp are mixed cultured on each mu of water (the proportion of silver carp and bighead carp is 5:1). In addition, soft-shelled turtles can not be co-cultured in crab ponds. If there are conditions, we can adopt the culture mode of mixed culture of appropriate amount of green shrimp in crab ponds, and use the measures of ecological culture and management to obtain high yield, high quality and high efficiency.

Fourth, release snails to meet the needs of river crabs for bioactive substances.

Snails are the most popular fresh animal bait for river crabs. Snails are benthic, slow in action and strong in water purification capacity. In adult crab culture ponds, live snails are put on each mu of water surface to stop their natural reproduction, which can provide a continuous supply of palatable and active protein bait for the whole growth process of river crabs. Among all kinds of snails, apple snail, which has the largest individual in freshwater snail culture, can be selected. Apple snail, also known as Oncomelania hupensis, has a thin shell, large individual, high meat content (edible ingredients account for 38% of body weight), miscellaneous eating habits, rapid growth, long breeding period and high multiplication. Transplanting apple snails in crab ponds can not only maintain the fresh water quality of crab ponds, but also provide natural bait rich in a variety of bioactive substances for river crabs, promote the rapid growth of river crabs and improve the listing specifications of adult crabs.

Fifth, adjust the water quality and promote the healthy growth of river crabs

The river crab has a high demand for water quality, which requires that the dissolved oxygen in the water should be kept at 5mg/L, pH 7-8.5, and transparency 30-40cm. The water level of the crab pond should be shallow in spring, deep in summer, autumn and winter, maintain a good water environment with good water quality, live, tender and cool, and promote the healthy growth of river crab. In the process of aquaculture, we must adhere to regular water injection. In the early stage, the water should be changed every 10 seconds and 15 days, and the water should be changed every time. In order to ensure the freshness of the water quality in the hot season, add some new water every day and change the water twice every week. In addition, 8-10g/m3 water is sprinkled with quicklime every 15 miles and 20 days. If there are conditions, it is best to regularly use photosynthetic bacteria or EM bacteria and other microbial agents to sprinkle water throughout the pool to improve water quality.

6. Do a good job in the prevention and control of crab disease

In recent years, with the continuous expansion of the scale of river crab culture, crab disease is also spreading and upgrading. Crab disease that has never existed before has also occurred in large numbers, mainly ciliosis of young crabs and trembling disease of adult crabs. It brings huge economic losses to the crab industry. Therefore, the prevention and treatment of crab disease should give priority to prevention, early detection, early treatment, no disease prevention, early treatment, and take different methods to prevent crab disease at different growth stages. Photosynthetic bacteria, EM bacteria and other microbial preparations were selected to regulate water quality. Prevention such as quicklime and dibromohydantoin are used regularly in high temperature season. In the period of high incidence of ciliates, chitin or ciliate should be used every 15 minutes and 20 days. In order to avoid drug resistance, drugs should be used alternately. Trembling disease is a kind of microorganism between bacteria and virus. Using enemy to kill the pool is an effective method to prevent and cure trembling disease.