For the pathogen, prevention and control measures are mainly to prevent the introduction of pathogens and the use of drugs to kill pathogens in the water body. Pathogens into people farms all of the following several ways fish seedlings, broodstock with pathogen and feed are contaminated with the pathogen and transportation tools with pathogens, headwater streams human pathogens, the birds with human pathogens. As the source of infection, disease of fish, fish is the most dangerous, farmers must be properly disposed of. Lurk in pond sediment of a large number of pathogens, especially bacteria and parasite eggs, which is advocated clear pond is one of the reasons. Fish pathogens are mostly in the condition of pathogenic bacteria, the most common pathogenic bacteria in our country. That is to say, this kind of bacteria is common in the water body, but only when the fish body’s resistance drops to cause the disease. Water is also a condition of the disease, only when the body has trauma or infection can be infected with the bacteria, otherwise it will not be infected with the water. But some pathogens is contagious, they enter the incidence of aquaculture water up to a certain number can lead to diseases. These pathogens including infectious pancreatic necrosis virus, infectious hematopoietic necrosis virus, sticky Cryptosporidium, Ichthyophthirius etc.. At present, antimicrobial drug use is still the main means of pathogen control, however, in addition to drugs and other measures can used to kill pathogens, has been adopted in the production of this type of technology, mainly useful ultraviolet lamp of pond water were irradiated to kill some pathogenic bacteria, photosynthetic bacteria, Bdellovibrio and biological prevention technology.
It is important to control and adjust the water quality. The deterioration of water quality and water quality is a very important and common factor affecting the resistance of fish. In the production process, the changes of dissolved oxygen, ammonia nitrogen, nitrite nitrogen, nitrite nitrogen, pH value, water temperature and salinity in sea water, etc.. In addition, the increase in the content of organic matter in the water body will be conducive to the breeding and propagation of pathogens. To control water quality must be to strengthen the daily management of aquaculture, can through the pond dredging, stocking density, moderate feeding control and change the water regularly and other measures to regulate water quality. Although there are reports that the environmental improvement agent has a certain effect on the water quality, but the use is not practical in production. In this regard, ecological control technology has great potential, the more successful examples of photosynthetic bacteria and gracilaria.
Drugs in the prevention of fish diseases in the process of role is only to control pathogens on the link, and in the fish body resistance to disease and the improvement of environment regulation role is very limited. However, fish once the disease, then only rely mainly on drugs, if the whole process of breeding from the above 3 aspects to consider, reduce the occurrence of disease, can choose to measure more, and once the disease, it can only rely on drugs.

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