HeLa is a crustacean, its growth is achieved by shelling again and again, whether the crab can be successfully shelled depends on the internal and external environment. If crabs do not shell out, they will die, causing loss of culture. Farmers should adopt effective methods to promote shelling of crabs based on the habits of river crabs to ensure successful breeding.
First, improve the water quality, and create an external environment for smooth shelling The crabs like to live in a water body that is fresh and rich in oxygen. Good water quality and superior environment can promote smooth shelling of crabs. It has been observed that the pH value of water quality suitable for growth and development of crabs is between 7.5 and 8.5. Water quality is slightly alkaline. Water transparency is required to be more than 40 cm. Water temperature is maintained between 20°C and 28°C, and dissolved oxygen is 5 mg/kg. Above the rise, the ammonia nitrogen content does not exceed 0.45 mg/l. In practice, the following methods can be taken to improve the water quality and create an external environment for crab shelling.
1. Change the water according to the season Generally, the interval between water changes in spring and autumn is 15 days to 20 days. In summer, it can be 3 days to 5 days according to the situation. When the day comes, it is necessary to pay attention to changing the water once a day. The old water in the pool can be discharged first, and then replaced with non-polluting and clean surface water and injected into the crab pool. The amount of water to be changed is preferably 1/3 to 1/2 of the total amount of pool water.
2. Frequent use of quicklime to raise crab ponds should occasionally spill the whole pool with calcined water, which can not only purify the water quality, but also increase calcium. The amount used is generally 15kg per mu of water surface. In particular, the places where the water change is difficult or the water with more mud in the pond should be used frequently.
3. Planting aquatic grasses and crabs Planting aquatic plants in the pond can both absorb the pollutants in the water, reduce the water body's fatness, clarify the water quality, and improve the transparency of the water body. It also facilitates crabs to hide and hide and avoid predators and is conducive to shelling.
4. Regulating the elevation of the water level The water level on the one hand can keep the water temperature within a suitable range, on the other hand it can stimulate the rapid shelling of crabs. In spring and autumn, the water level of the culture pond is generally reduced to facilitate the rapid rise of the water temperature. The crabs can be heated from the shallow water in the pool. In the summer, they should try to deepen the water level and strive to add 1.5 meters or so to keep the water temperature cool. When a large number of crabs were found to be shelling, the water level should be lowered to allow the crabs to shell in shallow water to avoid deep water levels and large water pressures, causing difficulty in shelling.
Second, to increase nutrition, to maintain a smooth shelling internal power crab each shelling time, the body will lose a lot of energy and nutrition, need to use new nutrients to supplement, crab body can grow up, weight will increase. According to the characteristics of the crabs during the shelling period, the proportion of animal feeds should be increased. At least 35% of the protein content in the feed should be ensured, and animal feeds such as wild fish and snail meat can be fed. Cooked vegetal foods such as wheat, pumpkin, etc., to avoid the single species of bait, resulting in lack of certain nutrients. Because of the large amount of minerals, vitamins, and other components, aquatic plants should be guaranteed for long-term supply. Prior to shelling, crabs have higher requirements for calcium. In addition to the frequent spilling of calcined water, calcium-containing substances such as eggshell powder and fish bone powder should also be added to the feed. In order to facilitate the regular shelling of crabs, it is also a good idea to add the dehulled meat when the crabs begin to shell.
Third, the prevention and treatment of diseases, so that the successful shelling unimpeded infection of pathogens will make crab body weight loss, affecting shelling. The crab ponds should also be completely cleared of ponds before stocking. Excessive silt should be removed from the pond to prevent the germs from hiding. When the crabs are stocked, they can also be used to disinfect crabs with 30 g/L to 50 g/L salt water. In the breeding process, chlorine dioxide, dibromohydantoin, and “highly effective disinfection spirit†should be used to kill bacteria. The best way to control the surface parasites of crabs is to use "fibrin nets" or a full-quantity splash of copper sulphate and ferrous sulphate mixture to make the parasites naturally fall off or die.
The infestation of enemy pests can also affect shelling and can be eliminated by artificial means. Normally, humans and animals should be harassed as little as possible at the poolside, especially when crabs are heavily shelled, crab ponds should be kept quiet. (Huang Yongfang)
First, improve the water quality, and create an external environment for smooth shelling The crabs like to live in a water body that is fresh and rich in oxygen. Good water quality and superior environment can promote smooth shelling of crabs. It has been observed that the pH value of water quality suitable for growth and development of crabs is between 7.5 and 8.5. Water quality is slightly alkaline. Water transparency is required to be more than 40 cm. Water temperature is maintained between 20°C and 28°C, and dissolved oxygen is 5 mg/kg. Above the rise, the ammonia nitrogen content does not exceed 0.45 mg/l. In practice, the following methods can be taken to improve the water quality and create an external environment for crab shelling.
1. Change the water according to the season Generally, the interval between water changes in spring and autumn is 15 days to 20 days. In summer, it can be 3 days to 5 days according to the situation. When the day comes, it is necessary to pay attention to changing the water once a day. The old water in the pool can be discharged first, and then replaced with non-polluting and clean surface water and injected into the crab pool. The amount of water to be changed is preferably 1/3 to 1/2 of the total amount of pool water.
2. Frequent use of quicklime to raise crab ponds should occasionally spill the whole pool with calcined water, which can not only purify the water quality, but also increase calcium. The amount used is generally 15kg per mu of water surface. In particular, the places where the water change is difficult or the water with more mud in the pond should be used frequently.
3. Planting aquatic grasses and crabs Planting aquatic plants in the pond can both absorb the pollutants in the water, reduce the water body's fatness, clarify the water quality, and improve the transparency of the water body. It also facilitates crabs to hide and hide and avoid predators and is conducive to shelling.
4. Regulating the elevation of the water level The water level on the one hand can keep the water temperature within a suitable range, on the other hand it can stimulate the rapid shelling of crabs. In spring and autumn, the water level of the culture pond is generally reduced to facilitate the rapid rise of the water temperature. The crabs can be heated from the shallow water in the pool. In the summer, they should try to deepen the water level and strive to add 1.5 meters or so to keep the water temperature cool. When a large number of crabs were found to be shelling, the water level should be lowered to allow the crabs to shell in shallow water to avoid deep water levels and large water pressures, causing difficulty in shelling.
Second, to increase nutrition, to maintain a smooth shelling internal power crab each shelling time, the body will lose a lot of energy and nutrition, need to use new nutrients to supplement, crab body can grow up, weight will increase. According to the characteristics of the crabs during the shelling period, the proportion of animal feeds should be increased. At least 35% of the protein content in the feed should be ensured, and animal feeds such as wild fish and snail meat can be fed. Cooked vegetal foods such as wheat, pumpkin, etc., to avoid the single species of bait, resulting in lack of certain nutrients. Because of the large amount of minerals, vitamins, and other components, aquatic plants should be guaranteed for long-term supply. Prior to shelling, crabs have higher requirements for calcium. In addition to the frequent spilling of calcined water, calcium-containing substances such as eggshell powder and fish bone powder should also be added to the feed. In order to facilitate the regular shelling of crabs, it is also a good idea to add the dehulled meat when the crabs begin to shell.
Third, the prevention and treatment of diseases, so that the successful shelling unimpeded infection of pathogens will make crab body weight loss, affecting shelling. The crab ponds should also be completely cleared of ponds before stocking. Excessive silt should be removed from the pond to prevent the germs from hiding. When the crabs are stocked, they can also be used to disinfect crabs with 30 g/L to 50 g/L salt water. In the breeding process, chlorine dioxide, dibromohydantoin, and “highly effective disinfection spirit†should be used to kill bacteria. The best way to control the surface parasites of crabs is to use "fibrin nets" or a full-quantity splash of copper sulphate and ferrous sulphate mixture to make the parasites naturally fall off or die.
The infestation of enemy pests can also affect shelling and can be eliminated by artificial means. Normally, humans and animals should be harassed as little as possible at the poolside, especially when crabs are heavily shelled, crab ponds should be kept quiet. (Huang Yongfang)
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