In the hatching process of fish fry, the phenomena of early release and malformation of embryo occur occasionally, which seriously affects the emergence rate. What preventive measures should be taken?
1. The rough wall of the hatchery must be smoothed with a grinding wheel
Gradually grasp the appropriate density when laying eggs, usually about 800,000 eggs per cubic meter of water; hatching water should be clean and pollution-free, and have a larger flow; acidic water, can be poured in the reservoir of lime slurry adjustment, so that The pH 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 the potassium permanganate solution can be poured into the hatching tank to make the pool water appear 5 to 10 The concentration of mg/L is maintained for 5 to 8 minutes. After treatment, the egg membranes of the fish eggs become firmer and less likely to be damaged, which has the effect of preventing premature release.
2, over-ripened fish eggs, and malnourished broodstock fish eggs, most likely to form deformed embryos
Changes in temperature, especially at the fertilization stage of the eggs, at the beginning of cleavage, and before and after the release of the membrane, can lead to an increase in abnormal embryos. Poor hatchery water quality also affects the normal development of the embryo and produces deformed 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.
3, sword water cricket is the biggest enemy of fish hatching stage
When it invades a large number of hatching ponds, it will bite fish eggs or bite dead fish. Therefore, spawning ponds and hatching pond waters must be strictly filtered. If it is found that there is more water in the hatchery pool, close the water inlet valve properly. The water intake is based on the fact that the fish eggs can be tumbling without sinking, and then 80% of the dichlorvos emulsion is poured into the hatching tank and immediately stir manually, every cubic meter. Rice pond water medication 200 ml, in the water temperature of 30 ~ 28 °C, 10 to 30 minutes can kill the pool of sword water scorpion. Or drill a few holes in a plastic bottle filled with 90% crystal trichlorfon, and hang it in the reservoir to the water supply port of the hatchery to poison the sword water cricket.
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