Explosive disease prevention and control technology of yellow jawfish
_Shen Xiujun
Yellow jaw fish is distributed in major river systems in China, especially in the middle and lower reaches of the Yangtze River, there is a large-scale aquaculture, is a freshwater farmed fish with high economic value. Since the beginning of spring this year, there have been large-scale outbreaks of yellow jaw fish deaths all over the country, after the incident, aquatic experts at all levels have gone deep into the front line to conduct epidemiological investigations, timely investigation of the condition, analysis of the causes, and the formulation of prevention and control plans, our city and county aquatic technology departments according to the Chinese Academy of Fishery Sciences Yangtze River Fisheries Research Institute on April 26 yellow jaw fish disease diagnosis report and May 9 provincial, municipal, county three levels of yellow jaw fish outbreak disease prevention and control analysis meeting opinions, combined with the previous stage of prevention and control work practice, Explosive disease prevention and control technology of yellow jaw fish is specially formulated for the reference of farmers.
First, the main symptoms and diagnosis of the onset of yellow jaw fish
Diseased fish swim alone, swim slowly, or lie still at the edge of the pool; the head of the sick fish is red or black, the skin on the surface of the body is ulcerated, covered with mucus, the body color is yellow or the rotting skin is decolored; the snout end, oral congestion, jaw, gill cover is hyperemia; the gills are basically clear and normal, occasionally the gills are swollen and a little mucus, there are a small number of wheelworm infections; the base of the dorsal fin, the base of the pectoral fin, and the caudal fin have ulceration and inflammation; the accumulation of abdominal fat is obvious, sometimes the ascites are serious; there is no food in the stomach and intestine, and sometimes the stomach is filled with viscous fluid; the intestine has congestion, redness and swelling lesions. Redness and bleeding of the anus; blood loss from the liver, blackening of the spleen, enlarged and necrotic kidneys, and enlarged gallbladder. Most diseased yellow jaws have typical symptoms of common bacterial diseases, such as "head perforation" disease, ascites disease, and rotting disease.
A variety of bacterial pathogens were isolated in the laboratory, including Aeromonas viriz, Edwardia, and O.d. shigrenoids.
Second, the causes of yellow jaw fish
(1) The pathogenic pond is generally a high-density monoculture mode, with a yield of more than 1500 kg per mu, the density is too large, and the variety is single;
(2) Pond management is lacking, water quality is deteriorating, water transparency is low, dissolved oxygen is low, and physical and chemical indicators exceed the standard. Ponds are basically not cleared and disinfected in winter, and plankton and beneficial microorganisms are not cultivated before the stocking of yellow jaw fish fry; (3) the amount of feeding during the temperature rise period from the end of March to the beginning of April is too large, and when the feeding of yellow jaw fish is normal, health care measures are lacking and prevention is not carried out in time;
(4) Farmers use ground cages, stall nets, drag nets and other operations to cause injuries to fish bodies, resulting in pathogenic bacteria or viral infections;
(5) Lack of scientific diagnosis after the occurrence of the disease, abuse of drugs, aggravation of the condition.
Excessive breeding density, excessive feeding volume, external stimulation (water quality, improper medication and artificial stimulation) are the main conditions for the onset of the disease, the combination of three factors under the decline of fish physique, reduced immunity level, infection with Edwardian bacteria and a variety of conditions of pathogenic bacteria caused by the outbreak of yellow jaw fish.
Third, the yellow jaw fish disease prevention and control methods
(i) Disease-free prevention
1. Thoroughly clear the pond before stocking the fingerlings to improve the bottom environment of the pond; apply bio-organic fertilizer to cultivate plankton and beneficial microorganisms;
2. Control the stocking density, and the pond culture mode should yield 750-1250 kg per mu;
3. Regular application of micro-ecological preparations in the breeding process to regulate water quality, maintain proper transparency and sufficient dissolved oxygen of the water body, and ensure that the water body is in a fat, live, tender and refreshing state;
4. Feeding high-quality feed, do not over-feed, especially when the feeding is strong, to control the amount of feeding, the daily feeding amount should be controlled within 1.5%;
5. Regularly add multi-dimensional, polysaccharide and natural plant antibacterial (antiviral) drugs to enhance the resistance of the fish body;
6. Do not use harsh drugs such as dichlorine, chlorine preparations, copper sulfate, etc., and mix multiple drugs at the same time to avoid fish body stress;
7. Farmers with conditions can soak with immune vaccines when the seeds are released to increase immunity.
(2) Onset of disease treatment
According to the pond area, water depth, water quality, water temperature and weather conditions, the dosage is accurately calculated and the drug is used accurately. There are three main ways to sprinkle disinfectant preparations, take antibiotics internally and Chinese herbal medicines.
1. The whole tank is sprinkled with disinfectants such as povidone iodine, chlorine dioxide or quicklime to kill pathogens. Before sprinkling quicklime, measure and confirm that the pH of the pond water body does not exceed 8.5;
2. Take florfenicol antibacterial drugs internally, refer to the instructions for drug use, ensure that the dosage is accurate, and the time is 4-5 days;
3. Take natural plant antibacterial (antiviral) drugs, such as houttuynia cordata, rhubarb, astragalus, large green leaf, plate blue root and other mixtures. Boiling water mixed with feed feeding or ultra-micro powder mixed with feed feeding can be. Dose is 0.5 g-0.8 g/kg Fish body weight for 5-6 days.
Fourth, other measures for the prevention and control of yellow jaw fish diseases
(1) Diseased and dead fish shall be treated without pollution. Timely fishing out of the sick and dead fish, quicklime disinfection and buried deeply to avoid further infection.
(2) Disinfection of breeding tools. Thorough disinfection and exposure of aquaculture tools, control the random discharge of infected pond water bodies into public ditches, and prevent the spread of pathogens.
(3) Go public for sale as soon as possible. Farmers can catch healthy adult fish in time at the beginning of the disease and reduce losses.
(4) Resume production as soon as possible. When the mortality rate of yellow jaw fish in the disease pond exceeds 70%, farmers can take measures to disinfect the water body, disinfect the bottom of the pond after drying the pond, fill the water quality with new hydroponic fertilizer, and carry out a new round of aquaculture production.
(5) Ensure the quality of seedlings. For newly released yellow jaw fish fry, it is necessary to ensure the health of the fry and control the occurrence of diseases from the source.