New techniques for healthy and high-yield culture of green shrimp in ponds

Macrobrachium rosenbergii, the scientific name of Macrobrachium rosenbergii, is a traditional breed in China. Because of its delicious taste and rich nutrition, it is favored by the market and consumers. Compared with Macrobrachium rosenbergii, Penaeus vannamei and other seedlings, the investment is less, the price is stable, and the breeding risk is small, so the green shrimp culture industry is relatively stable. However, with the continuous expansion of the scale of green shrimp culture and the increasing degree of intensification, the problems also emerge. at present, the most prominent problems are the serious inbreeding of green shrimp, the degradation of germplasm and the advance of sexual maturity. this brings problems to production: first, the growth of precocious green shrimp is slow, nutrition accumulates to gonadal development, the specification of commercial shrimp is small, and the market price is low, which directly affects the economic benefits. Second, precocious green shrimp propagate a large number of young shrimp, which rapidly increases the density of young shrimp in the pond, and the young shrimp and adult shrimp compete for food, oxygen and space, which leads to the failure of adult shrimp specifications, a great reduction in commodity prices, and affects the production of aquaculture, thus restricting the healthy development of green shrimp culture. How to improve the production, commodity specifications and economic benefits of green shrimp culture is a common concern of every shrimp farmer. Therefore, it is necessary to explore new culture models and find new culture techniques in order to achieve the goal of high quality, high yield and high efficiency. According to the breeding experience of previous years, combined with the actual production, this paper mainly introduces the new healthy and high-yield culture technology of green shrimp in pond for your reference. 1. Good pond conditions must be created: (1) adequate water sources, fresh water quality, no pollution, and in line with the national fishery water use standards. The dissolved oxygen is greater than 5mg/l, and the dissolved oxygen at the bottom of the pool should be more than 3mg. The area is 2-5mu and the water depth is 1.2m-1.8m; the bottom of the pond is flat with a slope of 1:2-2.5kW; each pond should be equipped with 1-2 aerators of 1kW and 1.5kW; the inlet is filtered with 80-mesh mesh bags to prevent wild miscellaneous fish and fertilized eggs from entering the shrimp pond. (2) cleaning pond disinfection: 7-10 days before stocking, the shrimp fry were sprinkled with 75-100 kg / mu quicklime in the whole pond to kill pathogens and enemy organisms. (3) fertilizing with water. 2-3 days after lime disinfection, 50-60 cm water was added and 150-200 kg / mu of fermented organic fertilizer was applied to cultivate natural bait organisms. (4) set up aquatic plants and concealment. Immediately after adding water to the shrimp pond, it is recommended that the water plants are mainly verticillium verticillata, supplemented by a small amount of grass, with a distance of 1-2 meters, planting grass in deep water and bitter grass in shallow water, accounting for about 30% of the water surface. The role of aquatic plants: can be used for green shrimp habitat, molting and concealment; photosynthesis can increase dissolved oxygen in water; purify water quality and prevent water quality from deteriorating. The production practice from various places shows that in the ponds with more water plants, the green prawns hold eggs late and the size is large. In addition, some tea branches and bamboo tips can be put in the shallow water of the shrimp pond. If possible, we can also lay nets and carry out three-dimensional culture, so as to increase the habitat of green shrimp, further improve the utilization rate of water body, effectively increase the yield and improve the specification of commercial shrimp. 2. Selection and purchase of high-quality shrimp fry and reasonable stocking: (1) Shrimp fry should be purchased from the original (good) seed farm of green shrimp, and must not be propagated and bred for many years in order to save cost. Select the shrimp seedlings propagated from different places or original (good) seed farms, as long as the density of shrimp seedlings in the breeding pond is moderate, generally controlled within 80-1 million pieces / mu, the specifications of the seedlings are relatively neat. Breeding shrimp seedlings with cultured shrimp as parents, due to inbreeding, the harmful genes of green shrimp continue to homozygous, so that the seedling quality is getting worse and worse, the sexual maturity is getting earlier and earlier, and the size of commercial shrimp is getting smaller and smaller. (2) the time of seedling release should be postponed appropriately. Most of the shrimp seedlings released in May and June have been sexually mature after 2 or 3 months of rearing, and a large number of offspring will be produced in August and September. If the stocking time is postponed to mid-late July, the phenomenon of autumn propagation can be controlled to a certain extent due to the sudden change of the living environment of green shrimp. (3) adjust the stocking density and carry out rotation fishing and stocking. The sexual maturity of shrimp is closely related to the stocking density sooner or later. The higher the stocking density, the earlier the sexual maturity. Reasonable density can not only ensure a higher yield of green shrimp, but also make the vast majority of green shrimp postpone laying eggs, accelerate their growth and reach larger specifications. The specific stocking density should be determined according to the culture model: green prawns are cultured exclusively in ponds, 60-80 000 shrimp fry of 1.5-2.0cm per mu are put in, and 1.5-20000 seedlings per mu can be released in mixed culture with conventional fish. Spring shrimp species, the density should not be too large, generally stocking specifications per mu 1200-1600 / kg shrimp species 8-10 kg, in order to ensure the cultivation and listing in May-June. In addition, after raising to September, measures should be taken to reduce the shrimp load in the pond and promote the growth of green shrimp. 3. Reasonable feed feeding: the green shrimp feed requires high quality and fresh, the size and particles are palatable, the crude protein content is 35-40% in the young shrimp stage, and the crude protein content is 30-32% in the middle and later stage (more than 4 cm). Feeding should follow the principle of "four determinations", and should be adjusted flexibly according to weather, water temperature, water quality changes and feeding conditions. 4. Strengthen water quality management and maintain good water quality. Green shrimp is not tolerant to hypoxia, and its oxygen consumption and asphyxiation point are higher than those of the main freshwater farmed fish. When there is a lack of oxygen in the fish pond, the green shrimp always floats its head and dies before the fish. Therefore, the regulation and control of water quality is the key to the success or failure and yield of green shrimp culture, and the water quality of shrimp culture must meet the requirements of "fat, live, tender and cool". The main measures are as follows: (1) Mechanical aeration. Due to the large quantity and high density of green shrimp, it is necessary to ensure that there is enough dissolved oxygen in the shrimp pond. 7, 8, 9 months every evening at 16:00 to 7:00 the next morning should start more aerator, muggy days or rainy days, during the day should also be properly turned on to increase oxygen. In particular, it is the high temperature season when the green shrimp seedlings are released in autumn, and the fishing and release of seedlings are generally carried out at low temperature in the morning, but this is the time of lack of oxygen in the pond water. If oxygen-increasing measures are not taken in advance, it is easy to cause anoxic death of shrimp seedlings. (2) often add new water or apply microbial preparations. Frequent injection of fresh water is the most effective measure to improve the environment of shrimp waters and maintain good water quality. Where the water source is convenient and the water quality is good, adding new water can increase dissolved oxygen, nutrients and trace elements, dilute the concentration of metabolites and toxic substances, and prevent the aging of pool water. In shrimp ponds which are short of water source or inconvenient to inject water, beneficial microbial preparations such as photosynthetic bacteria, EM and Bacillus should be adopted to improve and regulate the water quality. (3) timely apply topdressing to cultivate plankton, keep the water color as yellowish green or brown ideal water color, and control the transparency in 25-30 cm. Topdressing is generally appropriate to use mature organic fertilizer and urea, superphosphate and other chemical fertilizers. (4) regularly sprinkle quicklime, generally every 15-20 days with 15 grams / cubic meter of lime water sprinkled in the whole pool, play the role of sterilization and calcium supplement while regulating ph. 5. timely interculture of fish species to control the excessive reproduction of green shrimp: in the process of shrimp culture, in order to maintain a reasonable culture density in the shrimp pond and improve the commodity rate of green shrimp, when the larvae reproduce to a certain number, some fish species can be properly reared, which can not only maintain the biodiversity of the water body, but also control the excessive reproduction of green shrimp in the pond. The time of fish breeding is at the end of August and the beginning of September. The main species are silver carp, Xiangyun crucian carp, carp, Pelteobagrus fulvidraco and other species, the number should not be too much, generally put about 100 per mu. Let a large number of plankton and flea larvae before metamorphosis in the fish feeding pond, so as to control the number of young prawns. 6. Several methods to control the precocious puberty and density of shrimp: (1) improve the stocking mode: many breeders mainly reared shrimp with eggs, and carried out self-propagation, self-rearing and self-breeding. This model belongs to extensive shrimp culture, although the seedling cost is low, convenient and practical, but it is difficult to control the density, the specifications of listed shrimp are uneven, and the yield benefit is not high. Therefore, in order to improve the yield and benefit, some technical measures must be taken, such as changing coarse culture to intensive culture, changing egg-holding shrimp into high-quality shrimp seedlings, and changing one crop of shrimp into two crops of shrimp. (2) when flea larvae appear in the shrimp pond in the first ten days of September, the whole pond can be sprinkled with 20 kg / mu calcareous pulp to quickly increase the ph value, so that the young shrimp and flea larvae that have not yet metamorphosis can not stand the sudden change of water quality factor and die. 7. Strengthen the prevention and control of shrimp disease: adhere to the principle of "prevention first and health management". In addition to pond cleaning and disinfection, selection of high-quality shrimp seedlings, reasonable stocking and feeding, regular application of quicklime, dibromohydantoin and superiodinated quaternary ammonium salt to disinfect water bodies. Compared with Penaeus vannamei, river crab, fish and other diseases, green shrimp is much less. The main diseases are black Gill disease, red body disease, soft shell disease and so on.