Since the middle of the 20th century, with the development of the aquaculture industry, feed additives such as antibiotics, olaquindox, and quinoxone have been widely used around the world. The drug feed additives play a significant role in preventing diseases and promoting animal growth. However, the side effects and the resulting pathogenic bacteria produce drug resistance, toxicity, "three causes" (teratogenic, carcinogenic, mutagenic) and other drawbacks are gradually revealed. come out. The issue of residue, environmental pollution, and threat to human health has become a hot issue that aquaculture workers and health workers in all countries are concerned about. With the widespread application of animal micro-ecological agents in animal husbandry and other aspects, the application in aquaculture has also attracted more and more attention. Its good results have been confirmed by a large number of experiments and production practices. Microecological preparations have the advantages of small investment, high yield, no residual toxicity, no drug resistance, no pollution to the environment, etc., and fully demonstrate the superiority of using micro-ecological control technology, and it will certainly become the development direction of the aquaculture industry in the 21st century. one. The relationship between microorganisms and aquatic organisms in water There are differences in the composition of microbial communities in different water environments, even if the composition and quantity of microorganisms in different seasons of the same water area also change. However, in the same season in the same water area, the composition and quantity of microbial flora in the water are not contaminated, and they maintain the ecological balance among the microbial flora. The composition of microbial flora in water is mainly bacteria, in addition to bacteria, there are yeast, radiation bacteria, bacteriophages and viruses. With the pollution of water environment, the pathogenic microorganisms of human and livestock diseases such as Salmonella, enteroviruses, and Aeromonas hydrophila causing diseases of fish and shrimp, Vibrio hemolysin, Reovirus, etc. will also multiply in water. The microbial ecology in the water directly affects the growth and reproduction of aquatic organisms, and excellent water quality can maintain the ecological balance of the microorganisms in the water. When the water quality is contaminated or the water environment deteriorates due to unreasonable feeding and management, the imbalance causes the unconditional pathogen to become a harmful or virulent pathogen. As a result, diseases of farmed animals have been caused. When the fish is in a healthy state, there is also a relatively stable dynamic balance between the microbial flora in the external and internal environments. For example, on the surface and mucus of freshwater fish, the normal flora consisting of Pseudomonas, Achromobacter, and Aeromonas forms a first line of defense against the invasion of pathogenic bacteria. The reasonable coexistence of this condition is also affected by the eco-environmental physicochemical factors and pathogenic factors. Under the normal state, fish, microbes and the ecological environment constitute a dynamic balance. In a certain range, this balance is relatively stable. In the case that the density of external pathogens reaches or exceeds the normal value, the fish will not be affected. However, when the ecological environment is mutated or the water quality is contaminated, the normal microecological balance is destroyed, pathogenic bacteria are activated and multiply and secrete toxins or antibiotics, destroying the ecological environment of the microbial flora in and outside the fish. balance. As a result, fish are attacked by pathogenic bacteria. Therefore, the imbalance of microbial flora in water is the main cause of fish diseases. Microecological preparations have colonization, exclusion, and reproduction in vivo, and viable bacteria in ecological preparations are members of the natural micro-ecological flora that can antagonize unnatural microorganisms in the natural ecosystem after entering the habitat. Action, thereby inhibiting the growth of harmful microorganisms. Microecological preparations can stimulate the growth of intestinal immune cells, that is, increase local immune antibodies, enhance the body's resistance to diseases, and adjust the internal environment through "righting and eliminating evils", which can be used for many diseases (such as digestive system, urinary system, nervous system, endocrine). System, respiratory system, circulatory system and infection) treatment and prevention. two. Micro-ecological preparations for aquaculture The so-called fish micro-ecological preparations are viable micro-organism preparations that are made by using micro-organisms or substances that promote the beneficial use of animals, such as fish and shrimps, and special processing techniques. It can be used in water micro-ecological regulation, water purification, can produce a certain biological or ecological effects; can also be used to adjust or maintain the animal's intestinal micro-ecological balance, to achieve the purpose of preventing and treating diseases, improving health and promoting growth. With the gradual deepening of the study of microbial ecology, people have discovered a variety of beneficial microorganisms in the water. These microorganisms have a close relationship with water quality and aquaculture. The use of these microorganisms can improve water quality, prevent disease, and increase fish and shrimp production. Such as: using bacteriophage, myxobacteria, Bdellovibrio, and Bacillus, etc. to control the formation of harmful algae red tides, the use of photosynthetic bacteria to treat organic wastewater and water purification (Chen Shiming 1990), the use of Bdellovibrio to purify the lake water, remove the pathogenic Vibrio And E. coli (Si Zhidong 1995), the use of Vibrio anguillarum to purify water and clear Aeromonas punctiformis (Shao Guiyuan 1995) have achieved good results. Reports of microecological preparations for internal use are few except photosynthetic bacteria. Now there are compound bacteria preparations that can be used in aquaculture, such as "Probiotic King", "Caoyu Microecological Agent" and "EM Original Dew". These microbial preparations are made up of various beneficial microorganisms (Bifidobacterium, Bacillus) , photosynthetic bacteria, Bdellovibrio, Actinomycetes, Lactobacillus, Acetobacter, Yeast, etc.) are all multi-functional high-tech products that are produced in the process of their growth and their secretion and secretion It is through such a symbiotic and proliferative relationship that a matrix that grows with each other constitutes a complex and stable micro-ecological relationship.Three. Application of Microecological Agents in Aquaculture The application of microecological agents has been confirmed to have the following three characteristics: 1. Versatility, which has a growth-promoting effect, can increase the production of fish, shrimp, crab and other aquatic products, improve the quality of fish products, and has many functions such as enhancing physical fitness, preventing diseases, etc. It can improve the survival rate of fish species 5-20. According to reports, one month after the shrimp enters the pond, the “Kill of Probiotics†begins to be administered at a dose of 1 mg per kilogram of water, once a week, for three consecutive trials. The onset time of shrimp virus disease was 10 days longer than that of the control pool, and the yield was increased by 40%; 2. With wide adaptability, the existing aquatic special microecological preparations showed obvious effects in experiments in Sichuan, Liaoning, and Guangdong. The main reason is that it is mainly affected by aquatic organisms and the individual micro-ecological environment, while the external environment has a relatively small impact on its role, thus showing a good adaptability 3. High degree of safety, aquaculture microbial preparations All species are isolated from the microbial system of healthy aquatic animals, purified, cultivated, and then acted on aquatic animals without causing any harm to aquatic animals, or residues in water and fish. After a certain period of time, it will play a positive role, and after the validity period expires, aquatic animals will return to the state before the use of probiotics, and the micro-ecosystem will still be relatively stable and balanced. According to reports, the "grassfish microecological preparation" developed by the Beijing Fisheries Research Institute (Manufactured by Beijing Jingnan Fish Medicine Factory.) There are three main products: One is Grass Carp, which can significantly increase the growth rate of grass carp. Special-purpose microecological preparation No. 1; a "resistance-prone microecological agent No. 2" that can improve the survival rate of fish species; and a "universal-type microecological agent No. 3" suitable for various aquatic products. In terms of weight gain, all the preparations can be increased by 10-20% compared with the control group, and the immune capacity is significantly improved by the immunocytochemical test compared with the control group.In addition, the breeding period can be shortened, the feed coefficient can be reduced, and the living long distance transportation can be improved. The survival rate and the improvement of the flesh quality and color of the cultured products to make them closer to the natural production products show that the micro-ecological agents are beneficial and harmless, and they will play a greater role in the development of healthy breeding and green farming. As Professor Wei Wei, a renowned expert in microbiology in China, predicts: "An era of probiotics will surely emerge after the era of brilliant antibiotics.
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