Pathogen control in cold water fish culture

1. Establish a strict quarantine system when introducing and exporting fish eggs and fry, all aquaculture areas should strictly carry out quarantine to prevent and control the occurrence of diseases. Quarantine ponds shall be set up in breeding farms to isolate imported fish species, and only if there are no major diseases can they be temporarily reared. The quarantine pool is generally located at the end of the drain. The length of quarantine time should be determined by the transportation season, water temperature and disease characteristics. It takes 20 days when the average temperature is not less than 12 ℃, and it can be shortened when the water temperature is high, which is determined according to the lower the temperature, the longer the incubation period. If a new species is transplanted to a new area, it will take one year to quarantine due to sudden changes in climatic conditions. Because some parasites and microbes that do little harm to local fish species may cause serious harm to the introduced species.

2. Pond disinfection first drains the pond water, and then disinfects it once a month with quicklime 130kg / mu, or calcium cyanide 160 kg / mu, or 5% calcium hypochlorite. Environmental hygiene and cleanliness should be maintained in and around the breeding area. Non-staff vehicles and livestock are not allowed to enter the breeding area. Trichloroisocyanuric acid is sprayed and disinfected once a month in the environmental area.

3. Fish body disinfection using medicine bath method. The commonly used disinfection drugs are as follows. (1) Salt: the preparation concentration is 2%-4%, soaking for 5-10 minutes, mainly to prevent bacterial Gill rot, protozoa, third-generation insect disease and so on. (2) bleach (containing 30% available chlorine): the bacteria on the body surface and Gill can be killed by soaking with a concentration of 10: 20 mg / L for 10: 30 minutes. (3) potassium permanganate: the bacteria, protozoa and the third generation worms on the body surface and Gill can be killed by soaking in 10 mg / L and 20 mg / L for 30 minutes. Potassium permanganate is a kind of oxidant, which should be prepared now, and the water for medicine bath should choose clear water with less organic matter and backlight for medicine bath. (4) Volume iodine: disinfect fish eggs with 0.5% to 1.5% polyvinylpyrrolidone iodine at a concentration of 50 mg / L for 15 minutes, which can prevent viral diseases such as infectious pancreatic necrosis, infectious hematopoietic tissue necrosis, viral hemorrhagic septicemia and so on.

4. Tools disinfect all kinds of tools used in aquaculture, which often become vectors for spreading diseases, so workers and their rain boots, leather pants and gloves must be disinfected when entering and leaving the breeding area. Materials and fishing gear are for special use in the culture area and should be properly kept and disinfected before use. Vehicles entering the breeding area must be disinfected and strictly prevent cross-infection. The tools used in sick ponds should be separated from those used in other ponds to avoid bringing pathogens from one pond to another. If the tools are lacking and cannot be used separately, the tools used in the sick pond should be disinfected and used. General nets can be soaked in 20 mg / L copper sulfate aqueous solution for 30 minutes, dried before use; wooden tools can be disinfected with 5% bleach solution and washed in clean water before use.

5. disinfect the food farm and clean the food farm every day. during the epidemic season, bleach and trichlorfon should be sprinkled around the food farm regularly to sterilize and kill insects. The dosage should be determined according to the size, water depth, water quality and water temperature of the food farm, generally 250 grams 500 grams:

6. drug prophylaxis for the prevention of diseases in vitro. Chinese herbal medicine can be tied up into small bundles and put into retting water at the intake hole, or the whole pool can be sprinkled with fungicides and insecticides, so as to achieve the purpose of killing pathogens in vitro. The drug prevention of diseases in the body is generally taken orally, and the preventive drugs are mixed in the bait according to a certain amount to make granular drug bait for feeding. The types of drugs vary with various diseases, and try to use more Chinese herbal medicine and vaccines to avoid drug resistance.