Water quality management technology of freshwater crayfish

Freshwater crayfish have strong adaptability to the environment and tolerance to hypoxia, and can even directly use oxygen in the air, but if crayfish are exposed to hypoxia and water quality for a long time, their food intake will decrease, or even stop feeding, affecting its growth; at the same time, poor water quality can promote the mass reproduction of parasites, bacteria and other pests, leading to the occurrence and spread of diseases. When the water quality is seriously bad, a large number of crayfish will die, resulting in the failure of shrimp culture. Therefore, when culturing freshwater crayfish in high-density ponds, the pond water should be adjusted in time according to seasonal changes and water temperature and water quality, so as to create a good water environment.

Daily water quality management

1. Adjust the water level of the pond: the water level of the freshwater crayfish culture pond is determined according to the change of water temperature, and grasp the principle of "shallow in spring and full in summer". It is generally kept at 0.6-1m in spring. Shallow water is beneficial to the growth of aquatic plants, the breeding of snails and the molting growth of young shrimps. When the water temperature is high in summer, the water depth is controlled at 1-1.5 meters, which is beneficial to the freshwater crayfish to survive the high temperature season. When the crayfish overwintering, the water depth of the overwintering pool should be kept at about 1.5 meters to ensure that the crayfish will not be frozen to death or frostbite. When the weather is too cold or too hot, in order to prevent the occurrence of the limit temperature, the pool water can be properly deepened to stabilize the bottom water temperature.

2. Adjust the dissolved oxygen in the pond water: generally, the dissolved oxygen content in the shrimp pond water is kept at about 4 mg / L, which is more suitable for the growth and development of the lobster. Once the dissolved oxygen content is less than 1 mg / L, it will cause the lobster to suffocate. The effective way to prevent lobster from lack of oxygen is to change water or add new water regularly. Generally, in the spring and autumn seasons before May and after September, the water is changed every 10-15 days, and the amount of water is about 1-3 of the pool water; in May and June, the water is changed every 6-7 days, and in the high temperature season from July to September, the water is changed every 2-3 days, and the water volume is 30% of the pool water each time. Keep the water quality "fat, alive, tender and cool", and have enough dissolved oxygen, and the transparency of the pool water is controlled at about 35 cm. Under certain conditions, an aerator can be installed in the deep water of the shrimp pond to start the oxygen increase in time to increase the dissolved oxygen in the shrimp pond water. The principle of adding and changing water at ordinary times is not to change water during the peak period of molting, not to change water after rain, and to change water more when the water quality is poor. If possible, biological agents such as photosynthetic bacteria and nitrifying bacteria can be regularly sprinkled into the water to regulate the water.

3. Adjust the pH value of pond water: the range of pH value that lobster can live safely is 6-9, and the most suitable range of pH is 7-8.5. When the pH value exceeds a certain range, the high limit is 9.5-10 and the low limit is 4-5, which will directly cause the death of lobster. Even within the safety range, if it is beyond the optimal range, it will have a negative effect on the life activities of lobster. To adjust the pH value of pond water, raw lime water can be sprinkled every 15 days. When the average water depth is 1 meter, 10 kg per mu is used to keep the pH value of pond water between 7 and 8.5. At the same time, it can increase the concentration of calcium ion in water and promote the molting growth of freshwater crayfish.

Regulation and control measures of bad water quality

In the process of production, when it is found that the water quality is deteriorated and the freshwater crayfish come ashore, climb or even die, the following measures must be taken in time to regulate the water quality:

1. Change part of the old water first, sprinkle and disinfect the water with bromochlorohydantoin 0.3 mg / L, and then add new water.

2. The next day, sprinkle with 20 mg / L zeolite powder and 0.4 mg / L Yishuibao (Bacillus subtilis).

3. After that, microecological agents were regularly sprinkled into the water every 5 days or so. Make use of beneficial bacteria preparation to form dominant bacteria to inhibit the population quantity, growth, reproduction and harm degree of pathogenic microorganisms, decompose harmful substances in water, increase dissolved oxygen in water, and improve water quality. The application of photosynthetic bacteria, nitrifying bacteria, Bacillus, Bifidobacterium, yeast and so on can play the above role.