With the continuous development of the crab industry, although the small size crabs have a certain market, they are generally only available for ordinary consumers to eat or use for processing of drunk crabs. There is a risk of low economical aquaculture, and it is difficult to fight fierce competition in the market, and thus develop. Large-size and high-quality crabs (more than 200 grams of male crabs and more than 150 grams of female crabs) have become an inevitable trend in response to international and domestic markets, and are also the only way to significantly increase the income of fishermen. The author summarized several key control points in the process of promoting the large-scale and high-quality river crab technology in recent years, which are introduced as follows for reference of farmers.
I. Control points on the pond environment
The pond is the place where the crabs grow, and the crabs are mainly in contact with the bottom of the pool. The quality of the bottom of the pond is the most basic condition for the success of the breeding, and it is also the key to the water quality management in the later period. The environment at the bottom of the pool is good, and crabs grow quickly. Poor environment in the pool, the growth of the crab is inhibited and interfered with, even lead to its growth disorder and disease. In order to improve the breeding efficiency, the newly excavated pond should be soaked in water, changed water several times, and treated with quicklime. At the same time, in order to prevent pesticides or fishery residues in the pond, it is better to use 1 antidote before stocking. . The second is the Tangkou, which was cultivated in the previous year. After the aquaculture was over, it was necessary to promptly remove excessive silt and keep the silt thickness at 10-15 cm. The third is to carry out the necessary exposure, freezing and plowing to eliminate pathogens and promote the decomposition of organic matter in the sediment into inorganic salts.
Second, on the control point of crab seedlings
The quality, specification and stocking density of seedlings are the necessary conditions for developing large-sized crabs. The first is to fully understand the origin of the pro-crab crabs, their specifications, and the production process of the big-eyed larvae. It is better to choose the seeds with good reputation, mature production technology, and standardized breeder breeding grounds. The second is to breed crabs by themselves or choose locally grown crab species. It is best to choose a crab species with a size of 100-180/kg, a size that is basically neat, asexually mature, no stumps, no parasites, and strong vigor. Third, the crabs need to be dealt with before they are stocked. If the crab species takes a long time to leave the water, the crab species should be sucked as much water as possible before restocking. The method is to use a small amount of sprayer to spray water 1 or 2 times, each time between 5 and 10 minutes. A mild disinfectant should be used to disinfect the crab species before the crabs are planted in the pond. The pathogens and parasites caused by the crab species should be reduced. The general choice of amino acid iodine or special seedling disinfectants is better. The disinfection time depends on the specific drugs and crab species. Endure the situation. Fourth, the stocking density depends on the pond conditions and management levels. The stocking densities of ordinary breeding ponds are controlled at 500-600 pieces/mu, and the mouth of the installation of micro-aeration pipe facilities can be increased to 700-800 pieces/mu.
Third, control points for production inputs
The inputs for crab breeding production are mainly fertilizers, feeds, drugs, etc. This is not only the material basis for breeding large-scale river crabs, but also the key to improving the quality of river crabs. First, the pond should be fertilized before the stocking of crabs in order to promote the rapid propagation of beneficial algae in the water, provide nutritive and biological-based baits for the growth of early crabs, and increase the survival rate of seedlings. At the same time, it can improve the nutritional status and color of water, and inhibit the growth of moss. Fermented organic fertilizers are mainly used, and special biological fertilizers can also be applied. The transparency of the pool water is controlled at 30-40 cm. In the middle and later stages, the water quality should be regulated. The water with light color and high transparency can be properly used for fertilizer application. Improper fertilization causes changes in water quality, and the transparency of pool water is controlled at 40-50 cm. The second is that the feed should be based on special feed for crabs. The formulated feed has comprehensive nutrition, high water stability, easy absorption and digestion, and can reduce the in vivo stress response of crabs. The principle of “two-headed and intermediate-coarse†should be mastered for feed feeding, and reasonable adjustments should be made according to the different growing seasons, growth conditions, and external factors of crabs. Feeding should be conducted once in the early afternoon and once in the middle and late afternoons. Feeding is from 9 to 10 am, and the feeding amount accounts for 30% of the total feeding amount. It is fed from 16 to 17 o'clock in the afternoon and the feeding amount accounts for 70%. Third, drug use should be based on mild drugs to minimize the effects of drugs on river crabs and water environment. Lime is splashed once every 10 to 15 days. Each dose is controlled at 5 kg/mu. Microbial preparations should be sprayed once every 10-15 days, but should be used cross-disinfected with an interval of 5-7 days. The method of use should be based on the use of the specific microbial preparation.
Fourth, on the production management control point
Production management runs through the entire process of crab farming, and the level of management and finesse are the factors that directly determine the success or failure of breeding. One is the basic bait problem. The basic bait for crab farming is mainly aquatic organisms cultivated in ponds and snails for increasing investment. The cultivation of aquatic organisms is mainly rational fertilization, and fertilization should be carried out especially 5 to 7 days before the stocking of crabs. Fermentation is mainly organic. Fertilizers or specialized river crab bio-fertilizers have certain benefits for the early survival rate of crab species. In the later period, the fertilizer should be supplemented in a timely manner according to the water quality, requiring a small number of times. The snails are generally put more than two times, and the total amount is controlled at 400-500 kg/mu. Before the Ching Ming, the amount is 250-300 kg/mu, and from June to August, the total investment is 150-200 kg/mu. . The second issue is water quality management. The water quality requirements are “new, live, and excellentâ€. Water levels and water quality are regulated through timely injection and exchange of water. Generally, water is changed every 10 to 15 days from April to June, each time the water is changed by 1/5, and the water level is 60-80 cm. During the high-temperature season from July to September, the water changes 1 or 2 times a week. Each time the water is changed by 1/4, the water level is stabilized at 100 to 150 cm. Change the water first to remove some of the old water and then add new water. Change the water time is usually 10 to 11 am, it is not appropriate to add water in the evening, the temperature should not be too large, or easy to appear dead crab. At the same time, the quality of the water should be stabilized at 7.5-8.5 by applying the bottom modifier according to the water quality. The third issue is water grass. Aquatic grasses can be selected from the group consisting of Hydrilla verticillata, Chrysospora, Elodea, Vallisneria, Valerian, Aquatic peanut, duckweed, etc. The rational use of the growth characteristics of various species of aquatic plants allows cross-planting of as many species as possible to avoid monoculture of aquatic plants and control of aquatic plants. 30% to 60% on the surface of the water. The fourth issue is the "three defenses" problem, namely, preventing flight, preventing disease, and preventing stealing. Frequently check the integrity of the anti-escape facilities, especially during the dramatic changes in the weather and the sexual maturity of crabs in the autumn. Pay close attention to changes in the weather, especially before the dramatic changes in the weather in the rainy season, splash high-dimensional stability in the water, with an amount of 200-300 g/mu. During the sexual maturation period, we should catch temporary maintenance or sales. In the summer hot season, the water quality is easily deteriorated, and the crabs often have diseases. Attention should be paid to prevention. In addition to the use of microbial preparations and sediment modifiers to improve water quality and soil quality, some immune enhancers should be added in the feed to increase the quality of crabs. Immunity. Pay attention to stepping up at night to avoid unnecessary losses. Fifth, the issue of fattening in the later period. Late fattening of crabs is an important management measure to improve specifications. At this time, feed grade calcium dihydrogen phosphate should be splashed into the pond every 3 to 5 days to promote rapid calcification. Strengthen the regulation of water quality, keep the dissolved oxygen in water at 5 mg/L or more, accelerate the metabolism of crabs and promote the effective transformation of nutrition. At the same time, we must pay attention to the conservation of aquatic plants to prevent deterioration of the aquatic plants, leading to deterioration of pond water quality and sediment quality. In the later stage of production, feeds with higher protein content should be used, and fresh fish should be properly added to improve the crab's taste.
I. Control points on the pond environment
The pond is the place where the crabs grow, and the crabs are mainly in contact with the bottom of the pool. The quality of the bottom of the pond is the most basic condition for the success of the breeding, and it is also the key to the water quality management in the later period. The environment at the bottom of the pool is good, and crabs grow quickly. Poor environment in the pool, the growth of the crab is inhibited and interfered with, even lead to its growth disorder and disease. In order to improve the breeding efficiency, the newly excavated pond should be soaked in water, changed water several times, and treated with quicklime. At the same time, in order to prevent pesticides or fishery residues in the pond, it is better to use 1 antidote before stocking. . The second is the Tangkou, which was cultivated in the previous year. After the aquaculture was over, it was necessary to promptly remove excessive silt and keep the silt thickness at 10-15 cm. The third is to carry out the necessary exposure, freezing and plowing to eliminate pathogens and promote the decomposition of organic matter in the sediment into inorganic salts.
Second, on the control point of crab seedlings
The quality, specification and stocking density of seedlings are the necessary conditions for developing large-sized crabs. The first is to fully understand the origin of the pro-crab crabs, their specifications, and the production process of the big-eyed larvae. It is better to choose the seeds with good reputation, mature production technology, and standardized breeder breeding grounds. The second is to breed crabs by themselves or choose locally grown crab species. It is best to choose a crab species with a size of 100-180/kg, a size that is basically neat, asexually mature, no stumps, no parasites, and strong vigor. Third, the crabs need to be dealt with before they are stocked. If the crab species takes a long time to leave the water, the crab species should be sucked as much water as possible before restocking. The method is to use a small amount of sprayer to spray water 1 or 2 times, each time between 5 and 10 minutes. A mild disinfectant should be used to disinfect the crab species before the crabs are planted in the pond. The pathogens and parasites caused by the crab species should be reduced. The general choice of amino acid iodine or special seedling disinfectants is better. The disinfection time depends on the specific drugs and crab species. Endure the situation. Fourth, the stocking density depends on the pond conditions and management levels. The stocking densities of ordinary breeding ponds are controlled at 500-600 pieces/mu, and the mouth of the installation of micro-aeration pipe facilities can be increased to 700-800 pieces/mu.
Third, control points for production inputs
The inputs for crab breeding production are mainly fertilizers, feeds, drugs, etc. This is not only the material basis for breeding large-scale river crabs, but also the key to improving the quality of river crabs. First, the pond should be fertilized before the stocking of crabs in order to promote the rapid propagation of beneficial algae in the water, provide nutritive and biological-based baits for the growth of early crabs, and increase the survival rate of seedlings. At the same time, it can improve the nutritional status and color of water, and inhibit the growth of moss. Fermented organic fertilizers are mainly used, and special biological fertilizers can also be applied. The transparency of the pool water is controlled at 30-40 cm. In the middle and later stages, the water quality should be regulated. The water with light color and high transparency can be properly used for fertilizer application. Improper fertilization causes changes in water quality, and the transparency of pool water is controlled at 40-50 cm. The second is that the feed should be based on special feed for crabs. The formulated feed has comprehensive nutrition, high water stability, easy absorption and digestion, and can reduce the in vivo stress response of crabs. The principle of “two-headed and intermediate-coarse†should be mastered for feed feeding, and reasonable adjustments should be made according to the different growing seasons, growth conditions, and external factors of crabs. Feeding should be conducted once in the early afternoon and once in the middle and late afternoons. Feeding is from 9 to 10 am, and the feeding amount accounts for 30% of the total feeding amount. It is fed from 16 to 17 o'clock in the afternoon and the feeding amount accounts for 70%. Third, drug use should be based on mild drugs to minimize the effects of drugs on river crabs and water environment. Lime is splashed once every 10 to 15 days. Each dose is controlled at 5 kg/mu. Microbial preparations should be sprayed once every 10-15 days, but should be used cross-disinfected with an interval of 5-7 days. The method of use should be based on the use of the specific microbial preparation.
Fourth, on the production management control point
Production management runs through the entire process of crab farming, and the level of management and finesse are the factors that directly determine the success or failure of breeding. One is the basic bait problem. The basic bait for crab farming is mainly aquatic organisms cultivated in ponds and snails for increasing investment. The cultivation of aquatic organisms is mainly rational fertilization, and fertilization should be carried out especially 5 to 7 days before the stocking of crabs. Fermentation is mainly organic. Fertilizers or specialized river crab bio-fertilizers have certain benefits for the early survival rate of crab species. In the later period, the fertilizer should be supplemented in a timely manner according to the water quality, requiring a small number of times. The snails are generally put more than two times, and the total amount is controlled at 400-500 kg/mu. Before the Ching Ming, the amount is 250-300 kg/mu, and from June to August, the total investment is 150-200 kg/mu. . The second issue is water quality management. The water quality requirements are “new, live, and excellentâ€. Water levels and water quality are regulated through timely injection and exchange of water. Generally, water is changed every 10 to 15 days from April to June, each time the water is changed by 1/5, and the water level is 60-80 cm. During the high-temperature season from July to September, the water changes 1 or 2 times a week. Each time the water is changed by 1/4, the water level is stabilized at 100 to 150 cm. Change the water first to remove some of the old water and then add new water. Change the water time is usually 10 to 11 am, it is not appropriate to add water in the evening, the temperature should not be too large, or easy to appear dead crab. At the same time, the quality of the water should be stabilized at 7.5-8.5 by applying the bottom modifier according to the water quality. The third issue is water grass. Aquatic grasses can be selected from the group consisting of Hydrilla verticillata, Chrysospora, Elodea, Vallisneria, Valerian, Aquatic peanut, duckweed, etc. The rational use of the growth characteristics of various species of aquatic plants allows cross-planting of as many species as possible to avoid monoculture of aquatic plants and control of aquatic plants. 30% to 60% on the surface of the water. The fourth issue is the "three defenses" problem, namely, preventing flight, preventing disease, and preventing stealing. Frequently check the integrity of the anti-escape facilities, especially during the dramatic changes in the weather and the sexual maturity of crabs in the autumn. Pay close attention to changes in the weather, especially before the dramatic changes in the weather in the rainy season, splash high-dimensional stability in the water, with an amount of 200-300 g/mu. During the sexual maturation period, we should catch temporary maintenance or sales. In the summer hot season, the water quality is easily deteriorated, and the crabs often have diseases. Attention should be paid to prevention. In addition to the use of microbial preparations and sediment modifiers to improve water quality and soil quality, some immune enhancers should be added in the feed to increase the quality of crabs. Immunity. Pay attention to stepping up at night to avoid unnecessary losses. Fifth, the issue of fattening in the later period. Late fattening of crabs is an important management measure to improve specifications. At this time, feed grade calcium dihydrogen phosphate should be splashed into the pond every 3 to 5 days to promote rapid calcification. Strengthen the regulation of water quality, keep the dissolved oxygen in water at 5 mg/L or more, accelerate the metabolism of crabs and promote the effective transformation of nutrition. At the same time, we must pay attention to the conservation of aquatic plants to prevent deterioration of the aquatic plants, leading to deterioration of pond water quality and sediment quality. In the later stage of production, feeds with higher protein content should be used, and fresh fish should be properly added to improve the crab's taste.
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