August is a high-temperature season. In addition, some areas are affected by thunderstorms and typhoons. The water environment changes greatly, making it more difficult to manage breeding production and causing a variety of diseases. According to the national aquaculture disease forecast data in the same period in recent years and the weather conditions this year, we have predicted the prone diseases in August and put forward suggestions on disease prevention measures for reference.
I. diseases prone
In August, aquaculture should focus on diseases such as Grasscarp hemorrhagic disease, carp edema disease, Koi herpesvirus disease, crucian carp hematopoietic organ necrosis disease, cryptorchidism irritant disease, white spot syndrome, Decapoda iridovirus disease, acute hepatopancreatic necrosis disease, infectious subcutaneous and hematopoietic tissue necrosis disease, shrimp hepatoenterocystis.
(I) fish diseases
1. Grasscarp hemorrhagic disease:the pathogen is Grasscarp reovirus, which mainly endangers Grasscarp and herring. The onset temperature is 20 ℃ ~ 30 ℃. The gill cover or fin fin base of the sick fish is bleeding, muscle punctate bleeding, liver and spleen congestion. Jiangsu, Anhui, Zhejiang, Jiangxi, Henan, Hubei, Hunan, Guangdong, Chongqing, Sichuan, Ningxia and other provinces should pay special attention to and do a good job in prevention.
2. Carp edema disease:the pathogen is carp edema virus, which mainly endangers carp and Koi. The onset temperature is 17 ℃ ~ 30 ℃, especially at 20 ℃ ~ 28 ℃. Sick fish float up, pile up and swim around, their eyeballs are sunken, and sometimes their whole body is swollen at the stage of fingerling. The disease is acute and has a high mortality rate. Hebei and other provinces should pay attention to and do a good job in prevention.
3. Koi herpesvirus disease:the pathogen is Koi herpesvirus type III (also known as Koi herpesvirus), which mainly endangers carp, Koi and their variants. The onset water temperature is 18 ℃ ~ 28 ℃. The sick fish stopped swimming, with sunken eyeballs, bloody scales, pale patches and blisters on the skin, gill bleeding and a large amount of mucus or tissue necrosis. The disease is acute and has a high mortality rate. Henan and other provinces should pay attention to and do a good job in prevention.
4. Hemopoietic organ necrosis of crucian carp:the pathogen is carp herpesvirus type II, which mainly endangers crucian carp, goldfish and crucian carp hybrid varieties. The onset water temperature is 22 ℃ ~ 28 ℃. The body color of the sick fish is black, and the body surface is extensively congested or bleeding, especially the gill cover, jaw, chest and abdomen. The gill filaments are swollen. After dissection, light yellow or red ascites can be seen, and the liver, spleen, kidney and other organs are swollen and congested, and the swim bladder wall has spot or plaque congestion. Jiangsu, Zhejiang and other provinces should pay attention to it and do a good job in prevention.
5. Cryptorchidism irritans:the pathogen is cryptorchidism irritans, commonly known as”white spot disease” or”small melon worm disease in sea water”, which mainly affects marine fish such as Pseudosciaena crocea, pompano ovata and grouper, and the onset water temperature is 22 ℃ ~ 26 ℃. The outbreak of the disease can be induced when the content of organic matter in water is high, the water flow is slow, and the breeding density is too high. There are a lot of mucus and small white spots on the body surface and gills of the sick fish. Microscopic examination of the small white spots shows that there are round or oval, opaque body color, and slow rotating insects. Zhejiang, Fujian and other provinces should pay attention to it and do a good job in prevention.
(II) crustacean diseases
1. White spot syndrome:the pathogen is white spot syndrome virus, which mainly damages shrimp and Procambarus clarkii. The onset water temperature is 18 ℃ ~ 30 ℃. The sick shrimp stopped feeding and swam on the water near the pond when they were dying. The disease is acute and has a high mortality rate. Jiangsu, Zhejiang, Shandong, Guangdong and other provinces should pay attention to it and do a good job in prevention.
2. Decapoda iridovirus disease:the pathogen is Decapoda iridovirus 1, which mainly damages shrimp, Macrobrachium rosenbergii, Macrobrachium nipponense and Procambarus clarkii. The onset water temperature is 16 ℃ ~ 32 ℃, and shrimp is most susceptible to infection when their body length is 4cm ~ 7cm. The liver and pancreas of the sick shrimp are atrophic, the muscles are white, and the gills and feet are black. Hebei, Jiangsu, Zhejiang and other provinces should pay attention to and do a good job in prevention.
3. Acute hepatopancreatic necrosis:the pathogen is Vibrio parahaemolyticus, which mainly endangers shrimp, with acute onset and high mortality. Hebei, Jiangsu, Zhejiang, Shandong and other provinces should pay attention to it and do a good job in prevention.
4. Infectious subcutaneous and hematopoietic necrosis disease:the pathogen is infectious subcutaneous and hematopoietic necrosis virus, which mainly damages shrimp. The sick shrimp grows slowly and has abnormal epidermis. Guangdong and other provinces should pay attention to it and do a good job in prevention.
5. Shrimp hepatoenterocystis:the pathogen is shrimp hepatoenterocystis, which mainly endangers shrimp. The onset water temperature is 24 ℃ ~ 31 ℃. There are large differences in body length, thin individuals and dark hepatopancreas in the sick shrimp population. Guangdong and other provinces should pay attention to it and do a good job in prevention.
II. Suggestions on disease prevention measures
1. Strengthen water quality management. Pay attention to the monitoring of water quality changes, regularly monitor the water temperature, pH, dissolved oxygen, ammonia nitrogen, nitrite and other water quality indicators of breeding water body every week, and timely adjust and control if abnormal.
2. Control water depth and temperature. The water depth of the fish pond is generally controlled at 2m ~ 2.5m, and the water depth of the fish seed pond is generally controlled at 1.8m ~ 2.0m; The optimum water temperature for fish growth is 26 ℃ ~ 28 ℃. When the water temperature is too high, fresh water can be added for regulation. It is best to add water at about 14:00 on a sunny day. Do not add water in the evening to avoid causing fish floating.
3. Scientific feeding. When feeding feed, adhere to the”four fixed” principle of timing, positioning, quality and quantity, and flexibly grasp the feeding amount according to the weather, water quality and fish feeding activities, so as to prevent feed waste and water quality deterioration.
4. Strengthen the management of breeding production. Pay close attention to the weather conditions, take measures in advance to prevent dike collapse, net breaking, escape, etc. that may be caused by typhoon and rainstorm, and pay attention to personnel safety. Patrol the pond frequently, and insist on patrolling the pond three times a day in the morning, middle and evening. Maintain a reasonable density in the breeding pond and promote the growth of breeding organisms.