How do rural fish farmers prevent and cure fish diseases during overwintering?

Overwintering of fish is an important link in the process of freshwater culture. The success or failure of fish overwintering is directly related to the economic benefits of the year. However, over the years, many farmers have attributed the causes of death of overwintering fish to hypoxia, so they mainly take measures to increase oxygen and pay little attention to the prevention and treatment of fish diseases in management. over the years, many of the causes of death of overwintering fish are caused by the prevalence of fish diseases, so in fish overwintering management, attention should be paid not only to the changes of dissolved oxygen, but also to the prevention and treatment of fish diseases.

There are as many as 50 kinds of pathogens in fish during overwintering. According to our observation and the research of relevant scientific research institutions, it is found that the parasites are especially harmful to melons, oblique tube worms and bean worms, water mold is especially harmful to fungi, and algal diseases are particularly harmful to Tripterygium. When these diseases break out, the mortality rate of overwintering fish can reach more than 60%, and some of them are even wiped out. According to analysis, the main reasons for the prevalence of these diseases are as follows: first, overwintering fish ponds and overwintering fish are not strictly cleaned and disinfected, so that a large number of pathogens take people through the winter water. Second, the overwintering fish overweight is too low, the fish body is thin, and the immunity is decreased. Third, in the process of pulling the net, the fish body is seriously damaged. Fourth, the stocking density of overwintering fish is too high. In view of the above reasons, the following effective measures can be taken in prevention and treatment:

First, 100 kg of quicklime is applied before the overwintering pond is released, and the pond is cleaned by dry method to kill pathogens and wild miscellaneous fish.

Second, the pulling net operation should be careful, do not touch the fish body. Before entering the overwintering pond, the fish can be disinfected with the mixture of 3 parts of crystal trichlorfon, 5 parts of copper sulfate and 2 parts of ferrous sulfate to soak in 7ppm for 2 minutes.

Third, the fish preparing for overwintering must be cultivated in autumn, and the proportion of energy feed (corn flour, etc.) should be added to the feed structure. It is best to make the fatness of the fish above 4. The stocking density had better not exceed 2 kg per cubic meter of water.

Fourth, timely treatment of fish disease is found. The mixture of cupric sulfate and potassium permanganate at 5:2 can be used to make the pool water show a low concentration of 0.3-0.4ppm. The above harmful parasites can be killed in about 24-36 hours. When applying medicine, you can hit more ice holes and pour it into the water during the freezing period, and sprinkle it all over the pool when there is no ice. However, it needs to be reminded that some farmers still use the 5:2 mixture of copper sulfate and ferrous sulfate during the high temperature breeding period after the discovery of fish disease, which not only does not have a therapeutic effect, but accelerates the death of diseased fish. Because ferrous sulfate is a reducing agent, although it can also make the reduction of copper sulfate play an insecticidal effect, the reaction rate is very slow at low temperature, and ferrous sulfate often causes the mucus of fish to fall off, which increases the content of organic matter in water and reduces the efficacy of copper sulfate. At the same time, the increase of organic matter increased the oxygen consumption factor of overwintering water, which made the pond water anoxic and accelerated the death of diseased fish. Potassium permanganate is an oxidant, which can not only kill harmful protozoa, fungi and myxobacteria outside fish, but also react with organic matter in water to produce inactive compounds. While potassium permanganate oxidizes organic matter, it also increases the efficacy of copper sulfate. in addition, the retention time of these two drugs in water is also short, which not only has no side effects on sick fish, but also does not cause pollution. This is why potassium permanganate is used instead of ferrous sulfate during overwintering.