Comprehensive measures urgently needed for healthy crab breeding
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Name
Nanfeng Baby Mandarin
Size
S 3.5-3.8cm
Sharp
sweet.seedless and juicy
Origin
nanfeng,jiangxi,china
Supply period
from October to next May
Fresh season: From September to November
Cold storage season: November to next January
Packing
inner packing :1kg net weight / mesh bag
outer packing :9kg net weight/ carton
Delivery time
5-7 days after got buyer's deposit
Quantity/conveyance
25.2MTS FOR ONE 40RH CONTAINER
Payment Terms
L/C,T/T,
MOQ
1X40`HR
Shipment port
Shenzhen Port of China
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I. Severity of current crab pests and diseases With the continuous expansion of crab farming areas and the scale of farming, crab pests and diseases have become increasingly serious. Crab disease increased from more than 10 species at the beginning of the 1990s to more than 30 species at present, and developed from a partial victim to a large area victim. This year is the most serious year for crab disease. The author received calls, visits and letters from more than 100 people in July, August and September. These diseases and pests have caused serious losses to the crab farming industry. According to preliminary investigations, more than one-third of the country’s crabs have been damaged and economic losses have reached several billion yuan. In Jiangsu Province alone, more than one billion yuan is lost due to the damage caused by shivering (crab crabs). In 1997 and 1998, some crab-raising people in the southern part of Jiangsu Province suffered almost no harvest due to damage from water turtles, insects and leeches. The serious crab pests and diseases also greatly reduce the value of basic food and food safety. If these pests and diseases do not take effective measures to prevent and control, the booming crab farming industry will suffer serious setbacks.
II. Why crab pests and diseases are more and more serious There are many reasons for the increasing severity of crab pests and diseases, and they are complicated. At this time, only ten reasons are listed in terms of aquaculture ecology, germplasm, and pesticide use.
(1) Water pollution is increasingly serious. Raising aquatic products depends mainly on water. The water shortage is not good, and what aquatic products are not well-kept. This is especially true for crabs that require high quality water quality. In recent years, pollution from industrial "three wastes" and pesticides has become more and more serious. Contaminants have different degrees of toxicity to river crabs. Such as ammonia nitrogen, the concentration of 0.9mg / L, 0.06g / juvenile crabs in the 96 hours mortality was 50%, mercury, cadmium more than mg / L, cyanide more than 0.02mg / L, oils more than 0.05mg /L will be toxic to river crabs. Therefore, in the heavily polluted waters, the mortality rate of river crabs is greatly increased. For example, in the Yangtze River section from Nanjing to Yizheng in 1997, due to the collision of two oil tankers, fire broke out and contaminated the river. During this time, the crab mortality rate of several crab farms using the river water cited here amounted to more than 80%, resulting in losses of several million yuan.
(II) Construction of site selection Construction of crabs based on the characteristics of river crabs requires sufficient water sources in the crab area, wide water depth, convenient drainage and irrigation, less sludge, fresh water, abundant bait sources, and a ratio of 3:1 or more in the area of ​​deep and shallow water. , Submerged plants, emergent plants and floating plants are well-organized with a total coverage of 1/3 or more. At present, most people cannot do this completely. Some use standard muddy fishes for raising crabs; some continue to raise new ponds to raise crabs according to the standard structure of standard fish ponds; some use crabs, turtles, and Pomprist waters to raise crabs; Crabs; some platoons, irrigation ditch and canal integration, drainage and irrigation are all sewage; some water disinfection is not enough or no disinfection to raise crabs, and so on. How can this raise healthy and fat crabs? Obviously it cannot.
(3) The introduction or self-cultivation of pathogenic microorganisms of river crabs The breeding of river crab seed pathogens usually has two kinds: one is transmitted from the parents to the offspring, and the other is from seedlings and the environment. If we cause and use diseased or pathogenically latent and unsterilized seed, when the condition is mature, it can cause a certain crab disease epidemic or pandemic. For example, in the cities of Jintan, Liyang and Yixing this year, some crab farmers introduced pathogenic lurking crabs from the old crabs in the offshore areas, and most of them have shivering diseases. There are few aquatic grasses, many silt, high density, more ponds with more residual baits, and some crab farmers have very few cases of healthy crabs introduced from Nanjing and other places.
(4) Serious degradation of germplasm In recent years, there are many places that randomly introduce wild-type mating; Some nursery factories use the male and female crabs born of the same parent in the same pond as maternal inbreeding; some use precocious crabs with insufficient physiological development for one year. As breeding parents; some use individual smaller crabs to fill up; others have environmental pollution affect the development of individuals and groups, and so on. These practices have caused a considerable number of crabs to be seriously degenerated and deteriorated. Not only are individual generations younger than generations, but their disease resistance has also deteriorated year after year.
(e) The lack of oxygen in the water generally requires that the dissolved oxygen in the water be more than 5 mg/L. If it is less than 2 mg/L, the crabs will suffocate, and it will cause other diseases to occur and cause massive deaths. Over the years, the problem of lack of oxygen in the waters in many areas has become more and more serious. There are many reasons for lack of oxygen. Some of them are decomposed and fermented by large amounts of rotten grass, residual baits and excrement, and consume large amounts of dissolved oxygen. Some have too much plankton in the water and consume too much dissolved oxygen to cause hypoxia; Too many shading plants such as pu and phytoplankton greatly reduce the photosynthesis of phytoplankton, resulting in too little dissolved oxygen. Some also have excessive density of crab fish, insufficient oxygen to cause oxygen deficiency, etc., thus resulting in dissolved oxygen in some crab areas, especially In the hot season, dissolved oxygen is mostly below 4mg/L, and some are only 2-3mg/L, resulting in long-term and massive death of the crab.
(6) Inappropriate Crab Drugs When the river crab disease is endemic and the number of dead crabs increases, many crab farmers become frantic and use drugs indiscriminately. According to reports from some participants in Jiangsu and Zhejiang, one-third of the crab farmers have more than 100 yuan per mu of medicine. As a result, crab disease has not only failed to prevent and control the disease, but has increased the cost, resulting in some negative effects and increasing the resistance of pathogenic microorganisms. . Some of them also affect the offspring. For example, a large number of quinolone drugs in a nursery in Lianyungang cause stagnation, malformation, and high incidence. According to many experts at home and abroad, terramycin, erythromycin, penicillin, streptomycin, oxolinic acid, furazolidone, and other antibiotics used in aquaculture have failed.
There is also a big relationship between the poor application effect and the poor quality of the listed drugs. The vast majority of currently available crab drugs are imitations of the same type of fishery drugs, pesticides and veterinary drugs. Although there are many brands, most of them are low-level repetitions. For example, there are more than 80 kinds of disinfectant brands that use dichlorine and trichlorin as the main raw materials in China. Others use additives instead of crab drugs for sale in the city. At present, most crab drugs enter the market only through in vitro bacteriostatic and insecticidal tests. They lack reliable data on metabolism in vivo, lack of specificity for the prevention and control of crab disease, and also affect the use of results.
(7) The spread of the “cluster culture†system has exacerbated the occurrence of crab disease. The so-called “enclosure†system is the process of using crabs to bred commodities. After April and May, it will nourish part of the crabs and harvest at the end of the year. At that time, the catch was mature and left immature. The remaining crabs continued to be raised again and the crabs were added later in May. For this system, some crab farmers not only fail to see its harmfulness, but also think that it is a “good way†to make full use of the same and economic crabs. Is it a good idea? We have done some research: Some For the first year or two, the ponds with many plants have indeed improved well, but by the third year, serious diseases and insect pests have appeared in many ponds with less aquatic weeds, especially ponds with few plants have not only serious diseases but also large crabs. The killing of small crabs and soft shell crabs by the enemy is also very serious. The reason is: This "enclosure" system is inconvenient and cannot be cleaned thoroughly after the commercial crab is caught every year, because it will injure young crabs. Only a small amount of lime in the wine was dealt with, and the pathogens that lurked in the bottom mud and juvenile crabs were subject to a pandemic when the conditions and timing were ripe. In recent years, all areas where the "cultivation system" has been implemented are all crab diseases, especially the areas with the most severe shivering disease.
(8) Density of crab culture, breeding methods and feeding and management measures are not matched Generally speaking, crabs have high density and high risk of disease. But it is not absolute, mainly to see whether the crab-raising and feeding management measures can be matched. Xiaoshan Qianjiang Farm A crab farmer put 1,000 large crabs, acres of about 150 grams of 75 kg of crabs. Due to effective management and pest control measures, crab disease is rare. The author helped a Japanese aquaculture company to carry out a trial of factory-cultured crabs, producing 36 healthy crabs of 150 grams per square meter and a mortality rate of only 1/10. Conditions and individuals can also engage in high-density intensive culture. However, the current widespread problem is that blindly pursuing high density regardless of specific conditions leads to high morbidity resulting from high density. According to the participants of the training course, the crab ponds with a size of 1,500/mu or more are poorly managed and the river crabs are heavier. On the contrary, the number is less than 800/mu. Even if the management is extensive, there are few illnesses. Some are more efficient than high-density farming.
(9) The lack of nutrition is now a common problem is not feeding and management in accordance with the nutritional needs of crabs, so that crabs have a variety of nutritional deficiencies. If there is not enough feeding, the crab grows slowly and the body is thin; while some feedings are more, but due to the poor quality of the feed, they cannot meet their nutritional needs; some only feed plant foods and do not feed animals. Lack of protein caused by diets; some crab waters do not pay attention to supplements of inorganic salts such as calcium, magnesium and phosphate, making crabs difficult to shell out, and soft shells and other symptoms; some large amounts of lime without phosphate fertilizer, so that a serious lack of phosphorus, calcium and phosphorus The proportion is seriously distorted. Phosphorus is an important limiting factor for the normal growth and development of aquatic young people. Without phosphorus input or the amount of phosphorus is too small, crabs cannot grow and develop normally. The lack of nutrients in the river crabs will weaken the resilience and will increase the chance of various diseases.
(10) Some sudden high temperatures and sudden low temperatures do not add deep pond water in high temperature and severe winter seasons. Some water inlets and pool waters have too large a temperature difference. The river crabs suffer from various disease disasters because they cannot tolerate the large changes in temperature difference.
In view of the above ten reasons, in addition to the country's strengthening of macro-management this year, the majority of crab-rearing people must further study science and technology and vigorously advocate and do a good job of raising crabs.
III. Comprehensive measures for healthy breeding of crabs (1) Selection, planning and construction of crab waters should fully consider the ecological habits of crabs and create an ecological environment conducive to the growth and development of crabs:
1. Selection of waters Regardless of the type of crab rearing method, all water sources should be selected, such as abundant water sources, fresh water, cool fertilizers, dissolved oxygen, and abundant sources of oysters, which meet China’s Fisheries Water Quality Standards (TG35); Severe and difficult-to-control waters cannot raise crabs.
2. Make a good division and planning In order to facilitate feeding and management and centralized prevention and control of crab disease, we must first determine the area suitable for crabs; then we must plan roads, canals, gates, electricity, dams, housing, feed processing, and pharmaceutical distribution within the area of ​​crab cultivation. And other architectural layouts.
(1) Ponds Most of the newly built crab ponds and old crab ponds in China are not in compliance with the requirements for healthy crabs and are urgently needed to be changed. New pond to do 4 points: 1 area, large crabs, should be more than 10 acres, square, rectangular, polygonal, etc. can be; raising, crab dung area can be smaller, generally 2-3 The length of the square is 10-15 meters. The area ratio of the deep and shallow water area is 3:1. The deep water area can maintain a maximum water depth of 1.5 meters or more. The shallow water area can maintain a maximum water depth of 0.4-0.6 meters. The bottom should be high and low, ravines. Nourishing crabs, such as pond surface is narrow, the pond can not open trench gully. 3 The slope is generally 1:2.5-3 4 The irrigation and drainage ditch should be separated and the water inlet and outlet should be separated. The discharged sewage can not be re-injected into the crab-raising area. Laotang transformation depends on the specific conditions and capacity. The old fish pond and the old crab pond do not believe it. Most of the design and construction are unsatisfactory, and most silt produced in the bottom of the pond are thick, and there are more pathogenic microorganisms for organic matter and crab disease. If you do not reform, you can't raise your crab. The transformation of the old pond can be divided into two situations: one is a small area, the dredging project is not large, can be dredging, freezing sun; the second is the area, a larger amount of work, the pond water to dry, in At the bottom of the pond, some gullies and gullies are opened, dark grasses are planted with maggots, water peanuts, and other submerged plants such as Vallisneria diminutus and Hydrilla verticillata, in order to improve the ecological environment.
(2) If paddy fields do a good job of raising crabs in the fields, they can make the crabs and crabs work together to complement each other, reduce pests and diseases, and increase profits. To this end, planning and construction of crabs in rice fields should be based on the implementation of the new construction mentioned above. The difference is mainly the time and method of the excavation of the edge and the middle ditch. Generally speaking, in the year of the Spring Festival, the side, middle ditch and side embankment for the preparation of raising crabs and rice fields were dug to facilitate the disinfection and stocking of the crabs. . Before planting rice, rice was blocked with non-toxic plastic film around the rice field. After paddy rice was added with water, the rice was planted. When the rice seedlings were green or grew to a height of 20 cm or more, the rice was removed around the rice field to block the film and allow the crab to enter the rice field.
(3) Dashui surface Dashui surface referred to here mainly refers to water areas such as lakes, reservoirs and rivers. This type of water is not conducive to dredging and can only eliminate excessive weeds, rotten grass, ridges, oysters, and pu and other aquatic plants that are not conducive to the growth of crabs and major enemy organisms, in order to reduce pests and predators.
3, anti-escape facilities can not injure the crab water surface small and small crab areas should be fenced off; large water surface is mainly to in and out of the water to block jail, its edge may not fence. The barrier materials used should be non-toxic and non-abrasive to the crab.
4. New ponds with small disinfection and disease prevention areas and old ponds after transformation should be disinfected with quick-disposal chemicals such as quicklime, bleach, chlorine dioxide, etc. after the basic water is discharged; the water with large area can be restocked. The crab seedlings were disinfected with 30-40 kg of lime per amu a month ago. No matter which kind of water body can not be disinfected with drugs such as Malachite Green, sodium pentachlorophenol and other toxic residues with too much toxic and excessive time.
5, good species of plants to prevent crab crabs in the area of ​​good aquatic plants can purify water quality, increase dissolved oxygen and hidden substances, improve the ecological environment, provide some food, reduce predators and similar killing rate, reduce disease. To optimize the structure and control the coverage of the existing aquatic crabs, submerged plants, emerged plants, and floating plants account for more than one-third of the total water surface; for crab-free crabs, they must be planted as soon as possible after disinfection in clear ponds. Aquatic grasses and deep-water areas are suitable for planting aquatic plants such as Vallisneria, Hydrilla verticillata, Malay okra, and Hylocereus albus. In shallow water areas, weeds, water peanuts and other aquatic plants should be planted. Plants with more shade and light, such as alfalfa and rhizome, should not be planted. Numerous facts indicate that crabs are rarely found in grassy areas where there are many grassy grasses and deep waters.
(B) Reform is not conducive to the healthy way of raising crabs From the perspective of healthy crabs, there are many problems in the existing crab-rearing methods. For example, many people now store crab species after the Spring Festival. Crabs resume their growth, and they are vulnerable to injury and easy to get sick. In addition, crabs and commercial crabs are farmed in two places. Crabs are easy to be injured in the process of catching and they are easy to get sick. Some people are blind. The pursuit of high density and high yields has aggravated water pollution, increased the probability of killing and morbidity between each other, and the previously discussed “clustering†system, which is more prone to disease. Therefore, the system of raising crabs should undergo “four reforms and four demolitionsâ€: that is, the spring should be changed to winter and the spring should be changed; the rearing should be changed to different places for the stocking at the same place; the clan and dungeon should be cultivated as sub-opening; the high density should be changed. Species are appropriately thin.
(3) Production and selection of disease-free and robust crab seedlings is a prerequisite and foundation for raising crabs. To produce and select disease-free and robust crab species, in addition to requiring the relevant government departments to strengthen the management of seed production and circulation, seed producers and shoppers should strictly meet the requirements of each link. To produce disease-free and robust river crab seedlings (big eye larvae) in river crab nursery, we must use non-environmental drugs or Chinese herbal medicines to strictly sterilize nursery ponds, pro-crab breeding ponds and tools, and use disease-free robust crabs from large water surfaces. . In the process of promoting production, embryonic development and nursery, blind or overdose should not be used. In particular, drugs such as quinolones should be used as little as possible. Crabs out of the pool to meet the health and other quality requirements. After the new crab crab ponds have been newly built and transformed, they should be scientifically disinfected and planted with grass to create an ecological environment conducive to the healthy growth of crab species. In the cultivation process, microecological balance methods, such as the application of photosynthetic bacteria, can be used to maintain the reasonable density of planktonic plants and animals; more than a small amount of biological feed, suspended particulate foods, and their palatable dietary foods can be used. Protect and nurture water quality to promote good circulation and produce more healthy, high-quality crab species. For selection of crab fingerlings, it is first necessary to consider whether or not the seed to be selected is disease-free and robust. During the production process, if the seedlings are sick or have excessive doses in the production process, they cannot be used. It is worth paying special attention to the crab breeding grounds in areas where there is serious pollution in the fresh water of the sea and the old crab farms in the offshore areas. The crabs are more sick and should be carefully considered when selecting them.
(D) do a good job in water quality management Here to talk about the water quality management of crab breeding process. Do a good job of water quality management and create a good water environment, crabs can grow and develop healthily. The management of water quality during the aquaculture process should be targeted.
1. Managing water quality problems The management of water pollution discussed earlier is becoming more and more important, but the degree of pollution is not the same for each specific crab area. Therefore, we can only take corresponding measures in a targeted manner. If the ammonia in the pond water is high and the PH value is low, it is necessary to apply more lime. If the external water source is sufficient and good, then the water exchange solution will be adopted. For large water surfaces, it is mainly resolved by cutting off pollution sources and enhancing the self-purification capability of water bodies. Such as preventing the inflow of sewage, adjusting the culture structure and density, and protecting and increasing aquatic plants.
2. Management of water quality for seasonal changes The health status of open-air cultured crab species and commercial crabs is greatly affected by seasonal changes. Such as adjusting the depth of water, there should be differences in each season, in the middle and lower reaches of the Yangtze River, the general spring is 0.8-1.0 meters, summer is 1.2-1.5 meters, and winter is 1.2 meters.
3. Managing water quality according to the changing weather conditions Where there are good water sources, it is necessary to change the water in hot and hot weather in time. If the water body is seriously deficient in oxygen, it should be combined with oxygenation when changing the water.
4. Management of water quality according to the characteristics of different stages of production of crabs The requirements for water quality indicators in the three major production stages of breeding, breeding, and cultivation of crabs are different. After the test, they should be adjusted against conventional indicators.
5. Manage water quality in light of the monitoring situation. Observe and monitor the crab water area frequently and find that the problem is solved in time. If it is found that the flowers are floating, indicating that oxygen is in the water, oxygen should be increased in time; if the amount of calcium, magnesium and phosphorus in the water is small or the ratio is imbalanced, crab shells are difficult, and soft shell crabs are more, calcium, magnesium and phosphorus should be added in time. Adjust the ratio of calcium, magnesium and phosphorus, adjust the hardness of the water to medium-low (8-10 German degrees), and the total phosphorus more than 50 micrograms/liter; if the water body becomes too fat, the crabs will chaos and chaos, reflecting the abnormality, and the specific reason will be Check not to use, can apply microecological preparations. With this preparation, the beneficial bacteria species are mainly used to form dominant bacteria to inhibit the population, growth, reproduction and harm of pathogenic microorganisms, and to decompose harmful substances in water, increase dissolved oxygen, and improve water quality. Such as the application of photosynthetic bacteria, nitrifying bacteria, Bdellovibrio, Bacillus, Bifidobacterium, yeast, etc. can play the role.
(E) Strengthen nutrition and enhance disease resistance
1. Although there are many types of river crab diets, the total required protein content should be 35-46%. Other nutritious ingredients are comprehensive, and they are fresh and palatable and easy to digest and absorb. The cost is lower.
2, feeding bait according to seasonal changes. In the case of crabs and crabs, they will begin to cast a small amount of high-nutrient bait when the water temperature reaches 8 or above. After that, they gradually increase the amount of high-nutrient baits, and lower the summer and autumn high-temperature seasons to feed high-protein foods and feed more coarse material; after the autumnal equinox, they gradually increase. High-protein, high-energy bait truly achieves “middle and fine endsâ€.
3, according to different growth and development stages of feeding, larvae have over-transmitted unitary algae, rotifers, halogen, fish, egg tarts, suspended particles, etc. mainly bait crab stage fish paste, pig blood, soybean cake, The young crabs are mainly pellets; the crabs are fed with wheat, bran, soybean meal, vegetables, and spiral arsenic, etc.; and the crabs are cast snails, small trash fish, corn, soybeans, and granular materials. the Lord.
4, according to the need to adjust the amount of food and nutrients, as the last time you should invest less, otherwise, you should vote more; if you find crab hard shell, soft shell crab, you should increase calcium and phosphorus in the bait and off Chitin and other substances.
5. The compound materials of crabs should be formulated according to the nutritional requirements of each stage of crab development. In order to improve the disease resistance of the bait, photosynthetic bacteria, feed yeast, various enzyme products and other micro ecological preparations should be properly added to the bait.
