In the hatching process of fish fry, the phenomena of early release and malformation of embryo occur occasionally, which seriously affects the emergence rate. Early release occurs mostly during the period from the emergence of the caudal fin to the muscle-effect period of the embryonic development. The egg membrane ruptures or dissolves, and the embryo body that lost the protection of the egg membrane sinks to the bottom of the water and dies. cause 1. The ovulation density is too high, or the quality of the hatchery water is poor, and the pH is low or high. 2. Poor quality of fish eggs, or over-cooked eggs, egg membrane is thin and elastic and poor, easily damaged. 3. Several hatching ponds use recycled water at the same time, and the hatching time of each hatching pond is different. Early in the hatching pool, the hatching fish eggs are released and the egg-bound enzyme released into the water enters with the circulating water. The hatching pool of fish eggs caused early hatching of the eggs that hatched in the pool. 4. The inner wall of the hatching tank is rough, and it is easy to make the egg membrane floating and floating with the water flow be scratched. Prevention 1. Sword mink is the biggest enemy of the fry hatchery stage. When it invades a large number of hatching ponds, it will bite fish eggs or kill larvae. Therefore, spawning ponds and hatchery ponds must be strictly filtered. If more water is found in the hatchery, the water inlet valve may be closed appropriately. The amount of water in the tank is such that the fish eggs do not drip, or the plastic bottle containing 90% of crystal trichlorfon is used to drill a few holes. The water supply to the hatchery in the reservoir can also kill Jianshui. 2. Where the hatching tank wall is rough with a grinding wheel to smooth; grasp the right density when laying eggs, generally about 800,000 eggs per cubic meter of water; hatch water to clean pollution-free, and have a larger flow; acidic Water, can be used to control lime slurry in the reservoir, so that the pH value is maintained between 7 and 8. If a small amount of fish eggs in the hatching pond are found to be removed in advance, the inlet valve can be closed properly and permanganate can be closed. Potassium solution was poured into the hatching tank, so that the pool water showed a concentration of 5ppm to 10ppm, and kept for 5 minutes to 8 minutes. After treatment, the egg membranes of the fish eggs became firmer, not easily damaged, and had the effect of preventing premature release. 3. Over-ripened eggs and malnourished broods produce eggs that are most likely to form deformed embryos. Changes in temperature, especially at the fertilization stage of eggs, before and after the cleavage, and before and after the release of the eggs, drastic changes in the water temperature can lead to an increase in abnormal embryos; adverse hatching water quality will also affect the normal development of embryos, resulting in abnormal embryos. Therefore, once a year's fry breeding work, it is necessary to do a good job of broodstock cultivation, but also to select the right time for the appropriate broodstock production.
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