How to prevent death in autumn when the crab is harvested?

Every autumn, breeding river crabs enter the season of maturity and harvest, and at the same time, they also enter the stage of easy death. If we do not pay attention to strengthen the management, it may cause heavy losses due to the mass death of river crabs. How to prevent the death of river crabs in autumn? This should start from the following three aspects:

(1) from September to November every year, a group of river crabs that have grown for two years have changed from "yellow crabs" to "green crabs". Due to gonadal maturity and increased osmotic pressure in the body, they can no longer adapt to the freshwater low osmotic pressure environment. This kind of crab must escape to find a new environment, and eventually most of them will die naturally. These river crabs should be caught and sold in time to avoid losing their economic value because of natural death.

(2) to prevent death from indigestion. After the beginning of autumn, the temperature difference between day and night is large, the changes of air pressure and water temperature also increase, and the appetite of river crabs will change, which can easily lead to indigestion and death. This is what is usually called "bloating to death". In severe cases, it may lead to all deaths. Prevention and control measures include: improving water quality, disinfecting with lime water regularly; adding antibiotics and auxin regularly to food; not feeding or less feeding plant bait, and appropriately increasing animal bait, especially high-protein bait such as earthworms and field snails; feeding should be timed and quantified. When the water temperature drops, the amount of bait should be reduced accordingly.

(3) to prevent death from a "cold". In autumn, the temperature changes greatly during the day and night, and the water temperature varies greatly, sometimes even a difference of 10 ℃. The river crab is very uncomfortable, easy to "catch a cold" and cause difficulty in breathing and death. The preventive measures are: pay attention to adjust the water level to prevent drastic changes in water temperature; when injecting new water, the temperature difference should not be more than 3 ℃; keep enough water hyacinth, water peanuts and other cover plants on the surface, but the coverage area should not be larger than 1 inch of the water surface; deepen the water level when the weather changes.