2. Salinity. See Table 2-2 for the requirements of larval salinity at each stage. Larval culture requires stable salinity, slightly higher. However, in the late stage of shrimp larvae, the salinity can be appropriately reduced to promote molting. When salinity is low, it can be improved by adding salt. ?
3. Dissolved oxygen (DO) and dissolved oxygen level are important indicators to reflect the environmental quality of nursery water. Too low dissolved oxygen not only affects the normal metabolism of larvae, but even leads to the death of larvae due to hypoxia and suffocation. Dissolved oxygen should be kept above 4 mg/L. In order to maintain high dissolved oxygen in pond water, it is also very important to determine reasonable larval density and scientific feeding besides ensuring adequate aeration and changing water. ?
4. Because ammonia nitrogen is toxic to larvae, operators should attach great importance to it in the management of seedling water environment. Ammonia nitrogen usually refers to ionic ammonia nitrogen (NH4+-N) and nonionic ammonia nitrogen (NH3-N). Nonionic ammonia nitrogen is toxic to larvae. In pond water, these two kinds of ammonia nitrogen can be transformed into each other, which is greatly influenced by the temperature, salinity, especially pH value of pond water. When the concentration of ammonia nitrogen is constant, when the pH value decreases, the concentration of ionic ammonia nitrogen increases, which has less toxic effect on larvae. When the pH value increases, the concentration of nonionic ammonia nitrogen increases, and the toxic effect on larvae also increases. Changing water and supplementing oxygen are also necessary measures to reduce ammonia nitrogen content. In addition, the combination of live feed and artificial feed, less feeding, maintaining a certain density of single-celled algae and cleaning the dirt at the bottom of the aquaculture pond regularly are also effective measures to reduce the concentration of ammonia nitrogen.
5. Illumination, although shrimp larvae are not very sensitive to light, the development of fertilized eggs and nauplii should be cultivated in weak light. If the water color of flea larvae is dark, they can be cultured under strong external light (10000-20000 lux), but the breeding concentration of algae must be paid attention to to avoid the increase of pH value. ?
6. The color of water can be judged intuitively, which indirectly reflects the water quality of seedlings. The water color of seedling water is brownish yellow, and the living environment of larvae is stable when the water color is dark. Good water color also means that diatoms reproduce well. The darker the water color, the higher the organic matter content, which will cause the increase of ammonia nitrogen. Antibiotics, shrimp granules, shrimp slices, etc. Will cause the water color to deepen. At present, many nursery farms adopt the method of not changing water or changing water less. The water used for nursery is dark in color, but the water quality rarely deteriorates, which may be related to a large number of aeration and nitrifying bacteria in the water. ?