CATDOLL : CATDOLL: How to analyze and prevent acute bleeding in barracuda?

Barracuda farming

In recent years, the proportion of pike farming in the aquaculture industry in northern Jiangsu has gradually increased. Pike belongs to the genus of the order Mugilius. Its external morphology is similar to that of mullet, but its fat eyelids are not well developed. It lives in coastal areas and estuaries, and can also live in freshwater. It is a wide-temperature and wide-salinity fish. In Lianyungang, it is commonly known as tench, and it is farmed in both sea and freshwater. Due to environmental pollution and the promotion and popularization of pike farming under the mixed farming model, a series of diseases have occurred in pike, and acute hemorrhagic disease is the most widely spread, fastest-onset, and most harmful among various diseases. Lianyungang Yongdong Aquaculture Professional Cooperative proposed a cause analysis and prevention and control measures for acute hemorrhagic disease of pike after visiting farmers in northern Jiangsu and studying and analyzing various diseased ponds.

Causes of acute hemorrhagic disease in barracuda

Acute hemorrhagic disease of pike (commonly known as canthal disease by farmers in Lianyungang) is caused by infection with a variant of the grass carp hemorrhagic disease virus (GCRV). The grass carp hemorrhagic disease virus was originally the cause of grass carp hemorrhagic disease and was the first fish virus isolated in China. Years of mixed breeding have caused cross-infection of pike, resulting in variants. Because the symptoms of sick fish are similar to those of grass carp hemorrhagic disease, treatment according to the treatment method of grass carp hemorrhagic disease can only delay the onset of the disease, and the duration is short. After the symptoms are relieved for about 2 to 3 days, large numbers of fish continue to die until most of the fish die, with a mortality rate of about 85% to 95%. Farmers are terrified by the mortality rate and transmission speed.

Epidemic symptoms

Theoretically, the onset time of acute hemorrhagic disease of pike is from April to November, and the water temperature can occur at 9-36℃. However, in pike farming, it mainly occurs from summer solstice to winter solstice, and is more common after the beginning of autumn. This disease is easily confused with hepatobiliary syndrome. In the early stage, the sick fish will show mild congestion symptoms in the mouth, gill cover, eye sockets, fins and both sides of the fish body. The back is black from the head to the dorsal fin, and there is a small amount of food in the intestine. In the later stage, the congestion symptoms will worsen, the eyes will bulge, the liver and kidneys will enlarge, and some sick fish will have a swollen abdomen and ascites in the abdominal cavity. The entire back is black, the gill filaments are swollen and purple, and in severe cases, symptoms of gill rot and white gills will appear.

Diagnostic Methods

Pike acute hemorrhagic disease is generally divided into: incubation period, acute period and onset period. It is very difficult to diagnose the disease through immunology during the breeding process. Most farmers only know when they find dead fish. At this time, pike acute hemorrhagic disease has entered the onset period, which has posed a threat to pike breeding. The incubation period is generally 4 to 10 days. Pike has no obvious symptoms, and its feeding and activities are normal. The length of the incubation period varies depending on the water temperature. The higher the water temperature, the shorter the incubation period, and vice versa. It is basically impossible to determine whether it is infected at this stage. The acute period is generally 1 to 2 days. The sick fish stops eating, the color of the back becomes obviously darker, and it swims alone. Dissection shows punctate or block hemorrhage in the subcutaneous muscles, the liver appears grayish white or locally congested, the spleen and kidneys are enlarged with slight bleeding, the gallbladder is darker in color, and some gallbladders are lighter in color due to different virus strains, which is easy to be confused with hepatobiliary syndrome. The duration of the disease varies, ranging from 2 to 3 days to more than 15 days. During this period, the diseased fish will show symptoms such as bulging eyes and acute organ bleeding, and begin to die in large numbers.

Prevention and control measures

The prevention of acute hemorrhagic disease in fish is very important. The following points can be done in daily breeding to greatly reduce the occurrence of the disease: 1. Improve the bottom environment and regularly cross-use polyiron, potassium persulfate and bottom improvement products with Chinese medicine additives; 2. Disinfect the water environment with chlorine dioxide or povidone-iodine solution every half a month. It is recommended to use povidone-iodine solution for mixed fish and shrimp ponds, and the medication should be avoided during the concentrated molting period of shrimp; 3. Scientific feeding and management, feeding feed from regular manufacturers at fixed points, at regular times and in fixed quantities to improve the fish's disease resistance, do not overfeed, and maintain good water quality; 4. Remove water toxins, regularly use organic acid detoxification products from regular manufacturers to remove toxins produced by algae metabolism and death, as well as pesticide residues, heavy metal ions and other toxins that enter the water daily.

Because of the high salt content in seawater, the mineral and vitamin content of marine pike is higher than that of freshwater pike. In addition, the content of omega-3 fatty acids and taurine in marine fish is much higher than that in freshwater pike, which has a protective effect on the heart and brain.

1.

Improve the bottom environment and regularly cross-use polyferric, potassium persulfate and bottom modification products added with traditional Chinese medicine;

2.

Disinfection of water environment: Use chlorine dioxide or povidone-iodine solution for disinfection every half a month. Povidone-iodine solution is recommended for mixed fish and shrimp ponds, and medication should be avoided during the concentrated molting period of shrimps.

3. Scientific feeding management, feeding the fish with feed from regular manufacturers at fixed points, at regular times and in fixed quantities, improving the fish's disease resistance, not overfeeding, and maintaining good water quality;

Analyze the bleeding of the barracuda to see if it is caused by internal organs, epidermis or head. Analyze the symptoms to find out the cause. Prevention methods include: improving the bottom environment, disinfecting the water environment, and scientific feeding and management.