Detailed Explanation of Ten Measures for Disease Prevention in the Four Major Chinese Carps

I. Sun-drying the pond bottom One of the main purposes of drying the pond is to let the pond bottom be exposed to sunlight for a period of time, so that the organic matter at the bottom oxidizes.

II. Thorough pond disinfection Choose lumpy calcium oxide that has not absorbed moisture or weathered. Before use, dissolve it in water to become strongly alkaline lime powder or slurry lime water, which has a killing effect on various pathogenic bacteria and parasites, and can promote the calcification of silt and prevent the reproduction of bacteria.

III. Reasonable density Reasonable density means maximizing yield as much as possible according to your own farming environment and technical conditions, rather than unrealistically and blindly pursuing high yield; stock at an appropriate density under the fish-carrying capacity that the water body can allow.

IV. Reasonable combination A pond for the four major Chinese carps generally refers to a pond mainly culturing grass carp, with bighead carp (Aristichthys nobilis), silver carp (Hypophthalmichthys molitrix), crucian carp, mud carp and others stocked together. The purpose of reasonable combination is not only to consider the yield and output value of various fish, but also to consider the reuse of feed, so as to reduce feed waste and water quality pollution. With reasonable combination, the fragments of the pelleted feed, the leftovers from grass carp feeding, and their feces are eaten by omnivorous fish such as crucian carp, mud carp and common carp, and are utilized once again, greatly improving feed utilization. After the feces of various fish fertilize the water, it is beneficial to the growth of phytoplankton and zooplankton, which can then be eaten and utilized again by bighead carp and silver carp. In this way, the overall production cost of fish is ultimately reduced, while also reducing the pollution of water quality by residual feed?BR>

V. Vaccine injection The main purpose of vaccine injection is to prevent the "three old diseases" of grass carp: rotten gills, enteritis and hemorrhage. Grass carp are more prone to the three old diseases before reaching 2 jin in body weight, so all grass carp before 2 jin should be injected with the vaccine 2-3 times. Now in the Pearl River Delta region, grass carp fingerlings are basically given "shots", but among the injected vaccines, most are prepared by local personnel using homemade methods. The effectiveness of these vaccines is not easy to guarantee, and the negative effects are obvious. It is recommended that workers engaged in vaccine injection choose some regular, properly produced vaccines with better potency that are made by scientific methods.

VI. Disinfection of fingerlings Whether fingerlings are several cm in body length or 2-3 jin in body weight, before being put into a pond for culture, they must be treated by medicated bath. Fingerlings bought from others may carry pathogenic bacteria or parasites. Centralized treatment of fingerlings not only has low cost, but also good effect and convenient handling. When your own fingerlings are transferred between ponds, treatment by medicated bath is also an effective prevention and control measure.

VII. Regular disinfection Regular disinfection and the use of medicated bait feed require only a small amount of medicine, have relatively low cost, and will not affect fish growth. When fish actually become diseased, because medication is difficult to administer, it is impossible for every fish to receive treatment; it can only play a controlling role, and all of it treats the symptoms rather than the root cause. Most farmers have experienced this deeply: after medication is used in a diseased pond, it is effective in the short term, but after a period of time the disease recurs just the same. From March to November, disinfect the pond water body and treat the pond bottom once a month, and feed special medicated bait for 3-4 days each month, which can achieve effective disease prevention results.

VIII. Biological water conditioning Photosynthetic bacteria are beneficial bacterial strains selected through scientific methods. After artificially introducing beneficial photosynthetic bacteria and letting them multiply in large numbers in the pond, the reproduction of other harmful pathogens will be restricted. Moreover, photosynthetic bacteria mainly use their own biological functions to purify and treat organic matter at the bottom of the pond, reduce self-pollution during the culture process, and ease the pressure on the pond. It is worth noting that photosynthetic bacteria are also a kind of bacteria, and when disinfectants are used, they will be killed as well. Generally, 4 days after disinfection, the efficacy of most chlorine-containing disinfectants has basically disappeared, and we can introduce photosynthetic bacteria as soon as possible. If no fish are diseased, generally do not disinfect easily; you can keep from disinfecting for 60-80 days. But photosynthetic bacteria are not effective permanently. After using photosynthetic bacteria for 60-80 days, carry out a full-pond disinfection again, and reintroduce photosynthetic bacteria to cultivate beneficial bacteria anew. Photosynthetic bacteria are used relatively commonly in shrimp culture, and should also be vigorously promoted for the four major Chinese carps. At present, in most areas of the Pearl River Delta, not only is the pond water fertile, but even the water in rivers and creeks contains especially large amounts of organic matter. Introducing photosynthetic bacteria can effectively degrade organic matter, especially in ponds where large numbers of pigs and ducks are raised beside the pond, where photosynthetic bacteria should be used even more.

IX. Scientific aeration As long as aerators are used correctly, they can also achieve very good results in the prevention and control of fish diseases. The main point is to turn on the aerator for 1-3 hours from 2:00 in the afternoon to 3:00 in the afternoon during the hot summer months. Through the stirring of the water body, first, it can aerate and reduce the content of harmful gases in the water; second, it can accelerate the oxidation of organic matter in the water body and reduce the pressure of oxygen consumption by organic matter in the pond; third, it can increase the dissolved oxygen content of the pond water body. The ultimate goal is to create a better living environment for the fish, so as to enhance the disease resistance of the fish body.

X. Reasonable feeding Generally, the feed used is required to have balanced nutrition, and the lower the feed coefficient, the better, so that less feces is produced. Master the correct feeding method to minimize the digestive burden brought by fish eating feed, as well as the impact of overfeeding on pond water quality