CATDOLL : CATDOLL: Prevention and control technology of common diseases of river crabs

Prevention and control techniques of common diseases of river crabs

1. The tip of the crab's walking legs is damaged, forming black ulcers and rotting. Then white spots appear on the segments of the walking legs, carapace, and sternum, and gradually turn into black ulcers. In severe cases, the carapace is eroded into holes, and muscles or membranes are visible, leading to the death of the crab. The disease is caused by the infection of bacteria at the tip of the crab's walking legs. Prevention methods: (1) Use quicklime to thoroughly clean the pond and keep the water clean. In summer, add new water frequently to keep 5-10 cm of silt at the bottom of the pond. (2) In ponds with signs of disease, sprinkle 15-20PPM of quicklime mixed with water throughout the pond. Treatment method: Sprinkle 2PPM of bleach throughout the pond. Add sulfonamide drugs to the feed, adding 0.1-0.2 grams of drugs per kilogram of feed, and feed for 3-5 consecutive days. 2. Black gill disease: The gills of crabs infected with black gill disease change color. In mild cases, the left and right gill filaments appear dark gray or black. In severe cases, the gill filaments all turn black. The crabs move slowly and have difficulty breathing. This disease is commonly known as sighing disease. This disease often occurs in the late stage of adult crab culture. The deterioration of water environment conditions is the main cause of this disease. Prevention is the same as shell rot disease. 3. Limb rot disease: The abdomen and appendages of crabs infected with black gill disease rot. During the winter, the incidence of this disease is high. The appendages appear spotted rot. The spots change from yellow to gray and black. This disease is caused by injuries during catching, transportation, and stocking, or by infection caused by enemies during growth. Prevention methods: (1) Do not injure the crab body during catching, transportation, and stocking. (2) Before stocking, soak the crabs in a 2PPM furazolidone solution for several minutes before releasing them. Treatment methods: (1) Spray oxytetracycline or furazolidone in the entire pond at 0.5-1PPM. (2) Sprinkle 15-20PPM of quicklime throughout the pond for 2-3 times. 4. Edema: The abdomen, navel and lower part of the carapace of the crab are swollen. The crab crawls on the edge of the pond and refuses to eat. Finally, it dies in the shallow water of the pond. The disease is caused by the infection of the crab's abdomen during the breeding process. Prevention method: During the breeding process, especially when molting, try to minimize disturbing the crab to avoid injury. Treatment method: (1) Sprinkle oxytetracycline or furazolidone throughout the pond at 0.5-1PPM. 5. Saprolegniasis: Flocculent filaments grow on the surface of the crab, especially at the wound site. The crab moves slowly, eats less, and the wound does not heal, resulting in ulceration and spread of tissue at the wound site, causing death. The disease is caused by the crab being injured and mold invading the wound. Prevention method: (1) Do not injure the crab during the operation of catching, transporting, and stocking. (2) Add animal feed before a large number of molting. Treatment methods: (1) Soak the diseased crabs in 3-5% salt water for 5 minutes, and apply 5% phosphorus to the affected area. 6. Ciliate disease The joints, legs, carapace, forehead, appendages and gills of diseased crabs may be attached with ciliated protozoa. The diseased crabs have a lot of dirt on their bodies, and their ability to move and eat is weakened. In severe cases, they may die before dawn. The disease is caused by excessive reproduction of ciliates due to excessive pond water that has not been changed for a long time. Prevention methods: Change the pond water frequently to keep the water fresh. Treatment methods: (1) Spray 5-10PPM of 30% aldehyde throughout the pond. (2) Spray 0.7PPM of copper sulfate and ferrous sulfate (5:2) throughout the pond. (3) Soak the diseased crabs in a mixture of 0.5-1PPM of chlorhexidine and 5-10PPM of potassium permanganate. 7. The abdomen of crabs infected with slug disease is slightly bloated. When the navel cover is opened, milky white or translucent granular parasites of 2-5 mm and about 1 mm thick can be seen parasitizing on the appendages or sternum. The diseased crabs grow slowly and their gonads are underdeveloped. The meat of river crabs seriously parasitized by slugs is foul-smelling and cannot be eaten. The main cause of the disease is the high salt content of the pond water, the large-scale reproduction of slugs, and the spread of infection by larvae. Prevention methods (1) Thoroughly clean the pond and kill the slug larvae in the pond. Common drugs include bleaching powder, trichlorfon, formaldehyde, etc. (2) Mixing a certain amount of carp in the crab pond can inhibit the number of slug larvae. (3) In ponds with signs of disease, completely replace the pond water, inject new water (salinity less than 1‰), or move the infected crabs to fresh water to inhibit the development and spread of slugs. Treatment methods (1) Soak the diseased crabs in 5PPM copper sulfate solution for 10-20 minutes. (2) Soak the diseased crabs in 20PPM potassium permanganate solution for 10-20 minutes. (3) Sprinkle 0.7PPM of copper sulfate and ferrous sulfate (5:2) throughout the pond. 8. Molting failure disease: Crabs with molting failure have cracks at the junction of the posterior edge of the head and thorax and the abdomen, but they cannot shed their old shells. The whole body of the diseased crabs turns black and eventually dies. This disease is a common disease of pond crabs. The cause of the disease is related to the lack of certain mineral elements during the growth process. 9. Polycystic ovary syndrome: Generally, there are more parasites in the crab seedling stage. When there are a large number of parasites, the crab seedlings cannot molt and die. When there are many parasites on the gills of young crabs and adult crabs, they can also cause death. Prevention and control methods: Soak the crab body in IPPM Sanisol solution until the polycystic ovary syndrome falls off. The crab body is clean. 10. Shaking disease: The "shaking disease" of river crabs is extremely harmful to river crab farming. The disease develops quickly and has a high mortality rate. It only takes 2-3 days from the onset of symptoms to death. There are many forms of river crab farming, and the causes of the disease vary. However, the incidence rate is higher in ponds alone and in mixed fish and crab ponds with insufficient aquatic plants in the ponds, and the relative losses are also greater. The incidence rate is lower in rice field farming and river ditch farming. The main causes of river crab "shaking disease" are: ① Incomplete disinfection or no disinfection at all; ② Poor seed quality; ③ Incomplete feed nutrition and improper feeding; ④ Deterioration of the ecological environment of the breeding waters; ⑤ Infection through inlet and outlet water.

What are the successful cases of the “Xia Xia Jintan Model”?

In the golden autumn, crabs are plump and roe is yellow, and drinking wine with claws nourishes the tendons and marrow. Now is the season for river crabs to be on the market. As a seasonal delicacy, river crabs with thick crab roe and tender meat have become an indispensable delicacy on the table of Changxing people. In order to make river crabs more delicious, river crab farmers in Changxing recently participated in the national river crab "small, fine and high" family breeding Jintan model training course to learn advanced management experience of fishery technology and advanced river crab breeding models. This means that Changxing has officially launched the creation of the "Jintan model" for river crab breeding. In the autumn evening, there is peace: the soft sunset is reflected in the river pond, and water birds are quietly perched waiting for food. Corresponding to the quiet scene, on the bank of a river pond, Qian Jinyuan, the head of the Hongqiao Yangdang brand hairy crab breeding base, and the breeding staff are feeding the river crabs, and they are very busy. Affected by the previous weather, Yangdang river crabs had breeding problems such as "loss of appetite". In order to "take good care of" these "treasures", Qian Jinyuan and other farmers have focused on the daily scientific management of the breeding base. "We have an aquatic WeChat group, and the leaders of the Agricultural Bureau often push some scientific breeding methods in the group to remind us to take preventive measures." Qian Jinyuan said, for example, in the previous flood season and hot days, we managed the aquatic plants and water quality well, and often changed the bottom of the bait left over by the crabs and the feces excreted by the crabs. "Qian Jinyuan introduced that the taste of river crabs depends on the water quality and the quality of aquatic plants. Through scientific breeding, the weather has not affected the output of the breeding base at all, and the per mu output is expected to reach 170 kilograms. Now is the best time to taste river crabs, and Qian Jinyuan is not worried about sales at all. It turns out that he has many ways to open up sales channels and increase sales. "Our crabs are sold online, and people all over the country can eat hairy crabs from Taihu Lake. "Qian Jinyuan said that the cooperative relies on 12,000 acres of crab ponds to provide a steady supply of products, and has in-depth cooperation with Zhejiang University's e-commerce team, so it has no worries about sales. "So far today, we have received hundreds of calls, most of which are orders for river crabs." The reputation accumulated by Yangdang brand river crabs over the years makes Qian Jinyuan full of confidence. In order to take the road of brand development, Hongqiao Town established the Yangdang brand river crab professional cooperative in 2003, implementing unified breeding, unified "Yangdang" brand, unified packaging and sales, and the influence of Yangdang brand river crabs has expanded rapidly. Of course, the improvement of brand influence is due to the insistence on high quality. On the road of improving the quality of river crabs, the cooperative has never stopped. It not only controls the quality of crab seedlings from the source, but also realizes the ecological benefits of double harvests in one place and dual use of water through intercropping technology.

‍‍The "155" ecological and efficient breeding technology for crabs and shrimps in our district's ponds has recently passed the review of the provincial local standard review committee and has been recognized as a local standard in Jiangsu Province. As an advanced area in the national river crab industry and a key area for river crab breeding in the province, our district has continuously explored new technologies for crab and shrimp breeding and has been at the forefront of the province. In particular, in recent years, taking the ecological environment protection of Changdang Lake and the construction of modern and efficient agriculture as an opportunity, we have explored, demonstrated and promoted ecological and efficient breeding technologies such as microporous oxygenation for crabs and shrimps and "155" for crabs and shrimps, and promoted the transformation of scientific and technological achievements by strengthening the connection between production, education and research with relevant colleges and universities. Our district has been listed as the "Experimental Demonstration Base of the Public Technology R&D Center for River Crabs in Jiangsu Province" and the "Base for Fisheries Science and Technology Innovation and Achievement Transformation in Jiangsu Province", and has embarked on a path of ecological breeding of crabs and shrimps. After on-site inspections and listening to reports, the expert group conducted a special review of the content of the "155" breeding technology regulations for crabs and shrimps in our district's ponds, and finally recognized the "155" technology for crabs and shrimps as the "Jintan Model for Crabs and Shrimp". Zhou Xin, the head of the expert group and a researcher at the Freshwater Fisheries Research Center of the Chinese Academy of Water Resources, fully affirmed the prospects for the promotion and application of the crab and shrimp "155" technology in the province, and proposed amendments and additional comments on the definition of terms, water quality management, disease prevention and control of pond crab and shrimp "155" to ensure the standardization and operability of the standard. Through this review, the crab and shrimp "155" has been upgraded from a technical model to a local standard of Jiangsu Province, which will not only add new highlights to the work of bringing fishery science and technology into households in the region, but will also promote the process of fishery standardization and continuously promote the modernization of fisheries.

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In recent years, our city has made river crab farming a top priority in the construction of efficient agriculture. With scientific and technological innovation as the driving force, we have explored and created a number of new technologies and models that are leading in the province and even the country, such as the microporous oxygenation ecological efficient farming technology in crab ponds and the "631" model. Last year, the output of river crabs reached 14,500 tons, with an output value of 1.53 billion yuan, accounting for more than 70% of the city's total fishery output value. The per capita output value of river crab practitioners exceeded 100,000 yuan, and 10% of the per capita income of farmers in the city came from the river crab industry. The Changdang Lake area has successively become the "Jiangsu Province River Crab Healthy Farming Demonstration Zone", "National Chinese Mitten Crab Standardization Demonstration Zone", and "Ministry of Agriculture's Advantageous Export River Crab Farming Zone in the Middle and Lower Reaches of the Yangtze River". As Professor Wang Wu, a doctoral supervisor at Shanghai Ocean University and an expert in China's river crab farming industry, said, "When it comes to crab farming technology, the whole country looks to Jiangsu, and Jiangsu looks to Jintan. The unique model of Jintan river crab farming is the integration of ecology, efficiency, and technology." The "Changdang Lake" brand river crabs are famous inside and outside the province and in Southeast Asia for their green quality advantages and distinctive brand image, but how was the "national brand" created? First, optimize the layout of river crab industry with scientific planning as the guide. Based on resource advantages, regional advantages and industrial advantages, optimize the structure of river crab industry, combine it with the development of "one town one product" and "one village one product" characteristic industries, give priority to river crab industry layout, policy support and scientific and technological services, and build river crab industrial park into a pilot area for modern fishery development in the province and a demonstration area for promoting farmers' income. Second, take infrastructure construction as a starting point to enhance the development capacity of river crab industry. Grasp the construction of crab pond standardization, material equipment, ecological environment, etc., to provide basic guarantees for the development of river crab industry. Third, drive with scientific and technological innovation to improve the development level of river crab industry. Strengthen the construction of river crab breeding system, strengthen the innovation and integration of new technologies and new models for ecological and efficient breeding of river crabs, accelerate the pace of efficient development and utilization of fishery resources, and cooperate with Southeast University to build an Internet of Things system to ensure stable and high yield of river crab breeding. Fourth, take demonstration as the guide to promote the efficient and large-scale development of river crab industry. The construction of "Science and Technology into Household Demonstration Project" has cultivated a number of demonstration bases with their own characteristics, and the construction of industrial parks has accelerated the scale of ecological and efficient breeding of river crabs.

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