The method of improving the resistance of fish

In recent years, with the expansion of aquaculture scale, the improvement of aquaculture production and the deterioration of aquaculture environment, the diseases of farmed aquatic animals are becoming more and more serious, which restricts the improvement of aquaculture production to some extent. At present, under the condition of artificial culture, it is unrealistic to control and eliminate all pathogens. In order to control the occurrence of fish disease, the author thinks that we should first improve the fish resistance, supplemented by drug treatment, the effect will be better. Here are several methods to improve the resistance of fish for reference.

Stocking good varieties is the first choice to improve the resistance of fish. In recent years, with the expansion of culture scale, the increase of inter-regional introduction, coupled with artificial reproduction without renewing parents and inbreeding for a long time, resulting in mixed breeding varieties, degradation, early sexual maturity, decline in disease resistance and small listing specifications. Therefore, high-quality and pure seedlings should be selected for stocking varieties, and seedlings should be purchased from regular qualified nursery farms. It is necessary to understand the source, specification, breeding age and so on. The excellent varieties have the advantages of fast growth, large market size and strong disease resistance.

Scientific stocking changes the traditional way of stocking, from spring to winter. Low water temperature in winter, fish fishing, transportation, operation and so on are not easy to damage the fish. It can make the fish species release early, adapt to the environment early and start eating early. After the spring water temperature rises, immediately starts to feed, causes the fish body to recover quickly, enhances the fish body's disease resistance.

Reasonable mixed culture can make full use of water space, increase the yield per unit area of fishing pond, and play a good role in the prevention of fish disease. The parasites on different fish are not exactly the same. Some parasites can only live on a certain host, while other fish are immune to it. As a result of mixed culture, the individual density of this kind of fish is reduced. Mixed culture of silver carp and bighead carp can make use of excessive plankton in the pond and improve the transparency of the water body. Tilapia can feed on cyanobacteria in water and play a role in purifying water quality. Pelteobagrus fulvidraco can eat anchor fleas in water and reduce the occurrence of parasitic diseases. Therefore, reasonable mixed culture plays a certain role in the prevention of fish diseases.

Scientific selection of feed at present, there are many kinds of feed in the market, and some of them have high protein content. Although fish can grow rapidly in a short period of time after feeding, they are easy to get "rich diseases" such as liver and gallbladder, with decreased resistance, high morbidity and mortality, and difficult to cure. Therefore, we should choose high-quality fish feed and buy it from regular qualified and reputable feed manufacturers. Feed should not be supplemented with hormones that are harmful to fish and people. The feed should be fresh, complete with nutrients, free of pathogens, and not rotten. According to the different growth stages of fish, choose the feed with appropriate protein content, the general seedling stage content is 14%-18%, the adult stage, the protein content is 18%-22%, the culture of crucian carp and carp can be appropriately higher. Secondly, we should take bait scientifically and strictly adhere to the principle of "four fixed feeding". According to the fish size, different species, seasons, grasp the appropriate amount of feeding. Pay attention to the combination of fine and rough. When the feeding times are increased, the fish has no stomach and the feed stays in the intestinal tract for a short time. Under the condition that the total feeding amount is constant, the feeding times are increased and each feeding amount is reduced, so that the fish is always in a state of semi-starvation, which can improve the feed utilization rate and the resistance of the fish.

Live fish are temperature-changing animals that live in the water, and all their metabolism is carried out in the water. The utility model has the advantages of good water quality, high feed utilization rate, fast fish growth and strong resistance. Therefore, during the growing season, the water quality should be kept fat, lively and cool for a long time. First, it is necessary to change the water at the right time, change the bottom water regularly during the growing season, and let the sun shine on the water body as deeply as possible, so that the whole body of water can become an oxygen-rich area and promote the growth of fish. Second, the scientific use of aerators, promote the use of photosynthetic bacteria and other biological agents. Third, timely fertilization, through fertilization, bring nutrients to promote the growth and reproduction of plankton in the pond. On the basis of good application of base fertilizer, topdressing should be done according to the principle of "timely, less and diligent application". Fertilizer should be used after full fermentation and disinfection.

In the process of strengthening the management of aquaculture, we should pay attention to careful operation to prevent fish body injury, in the middle and later stages of culture, timely catch fish that meet the market specifications, reduce the density in the pond, and make full use of feed. At the same time, it is necessary to do a good job in the environmental hygiene of fishing ponds, diligently remove weeds on the edge of the pond, and eliminate enemy pests and intermediate hosts. Catch the residual bait and dead fish in time, clean and disinfect the food farm regularly.