Problems and Solutions in Crayfish Culture

First, the broodstock disinfection method is not properly. The conventional disinfection method is to soak lobster lobsters with a concentration of 3% saline, which is correct for broodstock transported with water. However, for broodstock transported by water, disinfection with salt water will aggravate the dehydration symptoms, which is not conducive to the improvement of survival rate. It is recommended to disinfect the broodstock with potassium permanganate instead of salt water.

Second, broodstock restocking time is not proper. At present, the source of crayfish seedling production is basically the same, that is, to put the broodstock to breed or buy the shrimp seedlings. Some farmers often experience some inappropriateness when formulating broodstock stocking and seed production programs, such as the stocking of wild broodstock for shrimp breeding in the first half of the year.

The suitable water temperature for crayfish mating and spawning is 12-33°C. Although the water temperature in the March-May period has reached the requirements for spawning, the gonad gonads before May have not yet matured. During this period, the crayfish do not lay eggs for mating. Shrimp eggs need to be developed after 4-6 months to enter the end of the IV period, so the first half of the stocked broodstock can breed shrimp in the second half.

Under natural conditions, crayfish are mostly spawned and hatched during the peak season from September to November. Shrimp eggs can hatch from 9-15 days after hatching. More than 80% of the shrimps in East China are hatched in October-December. Therefore, as long as the broodstock is introduced from August to October, shrimps for cultivation can be cultivated through natural breeding. Anatomy of crayfish broodstock It is known that some female ovaries have developed to stage II-III in March. By feeding high-quality feed and raising the temperature of overwintering water, the growth rate of female gonads can be accelerated, and early spawning and hatching can be achieved. . Therefore, combining broodstock greenhouse overwintering technology with pond aquaculture and rice paddy aquaculture can form a new breeding mode, which is beneficial to the improvement of crayfish aquaculture production and efficiency.

Third, a large number of fertilization caused the death of aquatic plants. Some farmers believe that aquatic plants mainly play a hidden role, and their feed function is not as important as plankton. Therefore, when the amount of plankton in the water is reduced, it is often adjusted by means of fertilization, and the transparency of pool water is therefore greatly reduced. When the transparency of the pool water drops below 30 cm, the plants in the pool are difficult to survive because of photosynthesis. The death of water grass not only reduces the feed source of the shrimp seedlings, but also leads to a decrease in the self-purification capacity of the water body and a deterioration of the water environment, which ultimately leads to a decrease in the efficiency of the biological feed cultivation and the feed utilization rate. This farming method not only has poor ecological effects, but also will eventually affect the production and efficiency of crayfish breeding. Therefore, we should pay enough attention to the cultivation and utilization of aquatic plants in the crayfish culture process.

Fourth, lack of understanding of the mutual benefits of fish and shrimp polyculture. Crayfish and fish polyculture is a breeding mode worthy of promotion. This is because fish and shrimp polyculture can coexist with each other. Residues and excrements of leftover fish can be used by crayfish to reduce feed wastage and not only reduce production costs. , And can reduce the pollution of water bodies. Therefore, the use of crayfish feeding characteristics to carry out polyculture of fish and shrimp, can achieve the purpose of mutual benefit and symbiosis, but also conducive to the improvement of aquaculture efficiency.

Fifth, there is insufficient understanding of the characteristics of crawfish fratricide. The fratricidal characteristics of crayfish are one of the important reasons that hinder aquaculture production. Tests have shown that the broodstock has a low residual rate of larvae and juveniles, which is related to the larval feeding characteristics of broodstock, while the broodstock has a higher killing rate for large-scale shrimp. In addition, the cannibalization rate among juvenile shrimps is much higher than that of adult shrimps. In particular, the survival rate of juvenile shrimps with large-scale shrimps is as high as 60%. Therefore, the large-scale killing behavior between shrimp and juvenile shrimp is the main factor affecting the survival rate of shrimp seedlings. In the production, attention should be paid to the setting of artificial concealed objects, such as water grass, asbestos tile, plastic pipe, and bamboo tube, for shrimps and adult shrimps to inhabit and hide. This can reduce the homicide rate and increase the aquaculture production.

6. Blind fertilization causes deterioration of water quality. At present, crayfish farming mostly adopts fertilizer and water to cultivate plankton feed, and the applied fertilizer is mainly organic fertilizer and compound fertilizer. However, after fertilization, the water body is prone to lack of oxygen. At the same time, the decrease in transparency of the water body leads to the death and decay of aquatic plants, and further worsens the ecological environment of the waters. A reasonable method of fertilization is to bury the organic fertilizer in the bottom sludge and compost it in the pond slope. This will produce a large number of benthic organisms for feeding broodstock and shrimp. The body of water requires moderate fatness and a transparency of 30-40 cm. When the grass grows vigorously, the transparency can be increased to more than 60 cm. In summer, the water temperature is high, and reasonable fertilization can prevent the hypoxia of the shrimp seedlings and the aquaculture environment from deteriorating. Therefore, the current fertility mode of Quanchiposa should be changed.

Seven, do not pay attention to timely change of water. Some farmers believe that crayfish can survive in the sewage ditch, and the water quality requirements are not high. In fact, under artificial breeding conditions, water pollution is one of the main reasons for the death of crayfish in large numbers. A proper amount of water change will not only help improve water quality, but also stimulate the crawfish clam shell, which will help speed up the growth rate and increase production. However, changing the water too often will also increase the cost of electricity or oil. The reasonable method is: change the water every 1-2 times in the high temperature season, change the water every time about 1/4. If the water quality is poor, bioorganic fertilizers can be used instead of organic fertilizers.

Sulphadimidine tablet are indicated for the treatment of the following diseases when caused by one or more of the following pathogenic organisms sensitive to sulfamethazine:
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