The whitebait is a species of bony fish which is a species of bream. The silverfish family has 2 genera and 8 genera and 20 species. According to the survey, there are 6 genera and 15 species in China. The current best-selling domestic and foreign markets are Taihu Lake New Silverfish and Big Whitebait. Baiyin is a small, wild and economic fish that inhabits the Changshuishui area. It is famous for its tender meat, delicious taste and high nutritional value. It is one of China's famous premium aquatic products and has long been known both at home and abroad. Making full use of the superior water quality conditions of inland waters and natural bait resources, and the proliferation of whitebait resources, have become increasingly valued by the aquaculture community. Practice has proved that once silverfish are transplanted at one time and they receive the fishery effect, they will benefit from sustainable use of fish, baits, and facilities as long as they use resources rationally. In order to ensure that the transplant is completely secure, a comprehensive analysis of the environmental factors of the whitebait into the water should be conducted. Move into the water body: Every water body in the natural world is a relatively independent ecosystem. Its geographical location, climate, geological structure composition, landform, soil, vegetation, water source and other factors are all different. These factors determine that each water area has a different Physical, chemical and biological properties. According to the investigation and test of the water of the transplanted whitebait, according to the biological and ecological characteristics of the whitebait itself, the following conditions should be considered for the migration of the whitebait into the water: Biological environment factors Fish composition: Composition of the fish community is simple In addition, there is a free living environment, especially in the water ecosystem, where the upper layer of biomass cannot be saturated. At the same time, the dominant population in the water body is examined. If the dominant domino of the water body is a fish with zooplankton and small fish and shrimp as the main food, silver should not be transplanted. Fish; If the dominant population is other predatory fish, silverfish transplantation is more appropriate. Injury fish: Silverfish are small in size and have a weak swimming ability. They are hunted targets of ferocious fish such as mackerel, redfish, whitefish, etc. Fierce fish caught in water should not exceed the total catch of the year. 15%, preferably below 5%. Zooplankton: Zooplankton is the main bait for the whole life cycle of the new silverfish in Taihu Lake and the juvenile fish stage. If the amount of zooplankton is large and the biomass is large, the silverfish will grow well, the population will multiply rapidly, and the fishery production will be high; otherwise the fishery production will be low. Therefore, moving into the water requires a rich zooplankton resource, with a minimum of at least 300/liter and a biomass above 1.2 mg/l. Phytoplankton: Phytoplankton is the bait of the zooplankton and is the basis of the bait of the whitebait. The amount of phytoplankton transferred into the body of water should not be less than 500,000/liter at least and the biomass above 1.5 mg/L. Small fish and shrimps: Small fish and shrimp are the main bait for the adult fish stage. Practice has proved that small and medium-sized fish and shrimps in the water are rich in resources, large silverfish grow well, individuals are large and their body length can be as long as 27 centimeters; small and medium-sized fish and shrimp in water are less in number, and the growth of big whitebait is poor and the plumpness is low. About 10 centimeters. Therefore, the body of water for transplanting large silverfish needs to be rich in zooplankton and there must be more small fish and shrimp. Non-biological environmental factors Water temperature: Non-biological environmental factors have the most complex effects on aquatic life, and the largest is the water temperature, which is the medium through which many physical and chemical factors play a role. If the water temperature rises from 20°C to 30°C, the dissolved oxygen in the water decreases by 17%. The temperature of water determines or changes the metabolism of aquatic organisms and the respiratory rate, blood circulation, enzyme conversion, and energy activation. The transplantation practice has proved that the silverfish have a relatively high temperature-tolerance, and the transplant has been successful in China's north to Jilin, Inner Mongolia and south to Fujian and Yunnan. The average water temperature for the silverfish transplantation water body is 10.9 to 17.6°C, preferably 15 to 17.5°C; the annual temperature change of the water temperature is 0 to 31.8°C; and the accumulated temperature of the life cycle is 3982 to 6430°C. Proper temperature during the breeding season: the fresh whitebait of Taihu Lake is 9.2-22.2°C; the large whitebait is 0.5-9.6°C, and the optimum water temperature is 3.8-5.5°C. Transparency: Transparency is an important indicator for evaluating water quality. The suitable transparency of whitebait into the water is 20-350 cm. Water body area: As with other physical factors, the water body area plays an important role in balancing the balance of energy and nutrients in water bodies. The practice of transplanting for many years proved that 0.2 to 450,000 mu of water can be successfully transplanted into the surface of whitebait. The area of ​​water is an important factor in determining the number of injections and the total output after successful transplantation. The author believes that the water surface of l ~ 100,000 mu is better, too large regular meeting will limit the quantity due to funds and other factors, the incubation period is too long, and the effect is slow; Due to the small total production in the future, the benefits are not obvious. Water level and water depth: The water level is relatively stable, and the water depth is preferably 5 to 15 meters. The water is too deep, it is not easy to increase the fat, affect the food biomass; too shallow, easy to dry in drought, will cause the work to be abandoned before transplantation. Spawning ground: Tests have shown that the hatching rate of gravel bottom is the highest and the hatching rate of silt bottom is the lowest. Dissolved Oxygen: Dissolved oxygen in water mainly comes from photosynthesis of the atmosphere and aquatic plants. Dissolved oxygen decreased with rising water temperature, reduced air pressure, and increased salinity. Dissolved oxygen is low, the food intake of fish is reduced, the feed coefficient is increased, growth and development are slowed down, and the resistance to disease is reduced. In severe shortage, it will cause death; dissolved oxygen is oversaturated, and the fish is susceptible to air bubble disease and die. The dissolved oxygen standard for fishery water in China is more than 5 mg/l, and the suitable dissolved oxygen for whitebait is 5.33 to 10.8 mg/l. Hardness, alkalinity, and pH: Hardness, alkalinity, and pH are important indicators for examining fishery water quality. According to investigations, the hardness of whitebait into the water is 1.78 to 6.29 meq/l, the alkalinity is 0.93 to 3.02 meq/l, and the pH value of the pH is 6.5 to 9.2. The quality of lakes (reservoirs) in China is mostly within this range and silverfish can be transplanted. Nutrients: Nutrients mainly refer to nitrates, phosphates, and silicates. Nitrogen, phosphorus and silicon are important nutrients needed by aquatic organisms and are important indicators for fishery water quality inspection. Nitrate can be directly used by aquatic plants and bacteria and participate in the material circulation of water bodies. The suitable nitrate concentration for silverfish to move into water is 0.075 to 1.919 mg/l. Phosphate affects the basic productivity of aquatic ecosystems and is an important factor restricting the growth of aquatic organisms such as algae. The appropriate phosphate content for the transfer of silverfish into water is 0.033 to 0.115 mg/l. Silicate is an important nutrient element of algae, especially diatoms. The content of silicates transferred into the body of whitefish is 1.22 to 6.85 milligrams per liter. In short, the migration of whitebait into the water requires a simple composition of the fish fauna. There are free habitats in the upper layers of the water ecosystem, less fierce fish, rich biological resources, moderate area, stable water level, water depth of 5 to 15 meters, gravel The optimum breeding site for bottom sediments has a dissolved oxygen content of 5.33 to 10.8 mg/l, fresh water, no pollution, and moderate physical and chemical properties.
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