How to Improve Fish Body Resistance? A Detailed Guide to Practical Methods

In recent years, with the expansion of farming scale, the increase in farming output and the deterioration of the farming environment, diseases of farmed aquatic animals have become increasingly serious, restricting the improvement of farming output to a certain extent. At present, under artificial farming conditions, it is unrealistic to control and eliminate all pathogens. To control the occurrence of fish diseases, the author believes that the first step is to start with improving fish body resistance, supplemented by drug treatment, and the effect will be better. Below are several methods for improving fish body resistance, for reference.

Stocking superior varieties is the first choice for improving fish body resistance. In recent years, with the expansion of farming scale, increased introduction of species between regions, and long-term failure to renew parent stock in artificial breeding, inbreeding has led to mixed and degraded farmed varieties, earlier sexual maturity, reduced disease resistance, and small market size. Therefore, the varieties stocked should be high-quality, pure fry and fingerlings, and fry should be purchased from regular, qualified hatcheries. It is necessary to understand the source, size, and breeding age of the maternal parent stock. Superior varieties grow quickly, reach a large market size, and have strong disease resistance.

Scientific stocking: change traditional stocking methods, and change spring stocking to winter stocking. In winter, water temperature is low, and catching, transporting, and handling fingerlings are less likely to injure the fish body. This allows fingerlings to be stocked early, adapt to the environment early, and begin feeding early. After the water temperature rises in spring, feeding begins immediately, so the fish body recovers quickly and its disease resistance is enhanced.

Rational polyculture: rational polyculture can make full use of water space, increase the yield per unit area of fish ponds, and also has a good effect on fish disease prevention. The parasites on different fish species are not completely the same. Some parasites can only parasitize a certain host, while other fish are immune to them. Because of polyculture, the individual density of this fish is reduced. Polyculture of silver carp and bighead carp can make use of excessive plankton in the pond and improve water transparency. Tilapia can feed on blue-green algae in the water, playing a role in purifying water quality. Yellow catfish can feed on anchor worms in the water, reducing the occurrence of parasitic diseases. Therefore, rational polyculture has a certain effect on preventing fish diseases.

Scientific selection of feed: at present, there are many feed varieties on the market, and some feeds have high protein content. Some feeds illegally add growth promoters, hormones, etc. After fish eat them, although they can grow quickly in a short time, the fish are prone to "diseases of affluence" such as liver and gallbladder diseases, with reduced resistance, high incidence and mortality, and difficulty in curing. Therefore, high-quality fish feed should be selected, and purchased from regular feed manufacturers with qualifications and good reputation. Feed must not add hormones harmful to fish and humans. Feed should be fresh, complete in nutrients, free of pathogens, and not rotten or deteriorated. According to different growth stages of fish, choose feed with appropriate protein content. Generally, the content at the fry and fingerling stage is 14%-18%, and at the adult fish stage, the protein content is 18%-22%. For farmed crucian carp and common carp, it can be appropriately higher. Secondly, feed scientifically, and strictly adhere to the four-fixed feeding principle. According to fish body size, different species, and season, master the appropriate feeding amount. Note that fine and coarse feed should be combined. Increase the number of feedings. Fish have no stomach, and feed stays in the intestinal tract for a short time. Under the condition that the total feeding amount remains unchanged, increase the number of feedings and reduce the amount of each feeding, so that the fish are always in a semi-starved state, which can improve feed utilization and fish body resistance.

Regulating water quality: fish are poikilothermic animals living in water, and all their metabolism is carried out in water. With good water quality, feed utilization is high, fish grow quickly, and resistance is strong. Therefore, during the growing season, water quality should be maintained as fertile, lively, and refreshing for a long time. First, change water in a timely manner. During the growing season, regularly replace bottom water so that sunlight can penetrate as deeply as possible into the water body, making the entire water body an oxygen-rich zone and promoting fish growth. Second, scientifically use aerators, and advocate the use of biological agents such as photosynthetic bacteria. Third, fertilize in a timely manner. Through fertilization, nutrients are brought in to promote the growth and reproduction of pond plankton. On the basis of applying base fertilizer well, do a good job in topdressing according to the principle of "timely, little, and frequent application." Fertilizer should be fully fermented and disinfected before use.

Strengthen management: during the farming process, pay attention to careful operation to prevent injury to the fish body. In the middle and late stages of farming, timely harvest fish that have reached market size, reduce the density in the pond, and make full use of feed. At the same time, do a good job in the environmental sanitation of fish ponds, frequently remove weeds around the pond, and frequently remove enemies and intermediate hosts. Timely remove residual bait and dead fish, and regularly clean and disinfect feeding grounds.