Crab seedlings, commonly known as “major larvae,†are the fifth stage of the larvae that have been peeled and become large larvae. It has a pair of compound eyes attached to the long end of the eye socket, which is named after the eye socket. Large-eyed larvae are the basis for breeding crabs and breeding crabs. The quality of these large-eyed larvae directly affects the survival rate of young crabs from phase II to V. Therefore, attention must be paid to the purchase of crabs.
First, understand the cultivation process of crab seedlings
Before purchasing crab seedlings, farmers should first understand the entire production process of the crab seedling farm, including: pro-crab size, feed use, breeding cycle, and so on. The pro-crabs used to propagate crab seedlings are best sourced from natural lakes and large bodies of water. The female and male crabs should come from different water areas to avoid inbreeding. Pro-crab size: Female crabs should not be less than 125 grams each, and male crabs should not be less than 150 grams each.
Crabs raised with Artemia (Artemia) are of better quality, and crabs cultivated with substitute feeds such as freshwater oysters and egg yolks are of poor quality.
In addition, the crab breeding cycle is generally 19 days to 21 days, when the water temperature at 21 °C.
Second, do a good job of crab quality identification work
1. The body of the high-quality crab was pale yellow, shiny and transparent. There were no foreign objects such as polypule or filamentous bacteria on the surface of the microscope. Inferior crab seedlings, dark body color, deep and shallow, milky white, orange, microscopic examination of crab seedlings, with insects.
2. High-quality crab seedlings are robust, uniform in size, have phototaxis, and are fierce in feeding and strong in retrogression. Feelings of crawling crabs are powerful and quick to respond with mouth blowing. Grab a small amount of crab seedlings by hand, shake the water and gently hold it into a mass, and immediately spread it after loosening it. Inferior crabs, empty stomach without food, poor swimming ability, easy to move in the bottom of the water, hand crabs easy to become a group, not easy to spread.
3. Crab size: normal crabs out of the pool size of 120,000 to 140,000 per kilogram is appropriate, not more than 170,000. Crabs that have reached this size will have less fake seedlings and become young crabs more smoothly. If there are too many crabs, it means that the crabs are of a short age and the carapace is soft and can not afford to operate and transport. If the number of crab seedlings is too small, the size of the crab seedling is large and it is close to the shelling period, and the shelling will die in transit.
4. Seedling water salinity, temperature: when the crabs go out of the pond, the water body should have a salinity of no more than 4 ‰, the desalination time should be no less than 7 days, and the water temperature at the time of emergence should be about 21°C. The temperature difference between the nursery pond water temperature and the culture pond should be 2°C. Up to 4°C is not exceeded.
Third, pay attention to matters
1. The day before the crabs go out of the pond, it is best to use drugs to disinfect once to kill some pests, reduce the occurrence of diseases during the cultivation, and also can eliminate some of the crabs with poor constitution.
2. When crabs are caught, they should be stopped and stopped, light traps should be used, crabs should have less impurities, and have strong vitality. Before packing, drain the water and put it evenly when it is put into the box to prevent crabs from crowding together and causing death.
3. Early Miao should choose to transport during the day, late Miao should be transported at night. Sun protection and wind protection during transportation. Motor vehicle transportation, when the car closed the doors and windows, open the doors and windows when parking, ventilation, no smoking in the car, spray water every 2 hours on the way, increase the humidity of the crab seedling box.
4. After the long-distance transportation, the crab seedlings have been basically dehydrated. If they are directly put into water, the crab seedlings tend to produce air bubbles and affect the survival rate. So before the crabs enter the pool, there must be an adaptation process: first open the crab box, sprinkle the crab seedlings for 5 minutes, soak the crab seedlings box and the crab seedlings in the pool water, and then leave the water on the shore and repeat after 15 minutes. Once, finally let the crabs go into the pool slowly.
First, understand the cultivation process of crab seedlings
Before purchasing crab seedlings, farmers should first understand the entire production process of the crab seedling farm, including: pro-crab size, feed use, breeding cycle, and so on. The pro-crabs used to propagate crab seedlings are best sourced from natural lakes and large bodies of water. The female and male crabs should come from different water areas to avoid inbreeding. Pro-crab size: Female crabs should not be less than 125 grams each, and male crabs should not be less than 150 grams each.
Crabs raised with Artemia (Artemia) are of better quality, and crabs cultivated with substitute feeds such as freshwater oysters and egg yolks are of poor quality.
In addition, the crab breeding cycle is generally 19 days to 21 days, when the water temperature at 21 °C.
Second, do a good job of crab quality identification work
1. The body of the high-quality crab was pale yellow, shiny and transparent. There were no foreign objects such as polypule or filamentous bacteria on the surface of the microscope. Inferior crab seedlings, dark body color, deep and shallow, milky white, orange, microscopic examination of crab seedlings, with insects.
2. High-quality crab seedlings are robust, uniform in size, have phototaxis, and are fierce in feeding and strong in retrogression. Feelings of crawling crabs are powerful and quick to respond with mouth blowing. Grab a small amount of crab seedlings by hand, shake the water and gently hold it into a mass, and immediately spread it after loosening it. Inferior crabs, empty stomach without food, poor swimming ability, easy to move in the bottom of the water, hand crabs easy to become a group, not easy to spread.
3. Crab size: normal crabs out of the pool size of 120,000 to 140,000 per kilogram is appropriate, not more than 170,000. Crabs that have reached this size will have less fake seedlings and become young crabs more smoothly. If there are too many crabs, it means that the crabs are of a short age and the carapace is soft and can not afford to operate and transport. If the number of crab seedlings is too small, the size of the crab seedling is large and it is close to the shelling period, and the shelling will die in transit.
4. Seedling water salinity, temperature: when the crabs go out of the pond, the water body should have a salinity of no more than 4 ‰, the desalination time should be no less than 7 days, and the water temperature at the time of emergence should be about 21°C. The temperature difference between the nursery pond water temperature and the culture pond should be 2°C. Up to 4°C is not exceeded.
Third, pay attention to matters
1. The day before the crabs go out of the pond, it is best to use drugs to disinfect once to kill some pests, reduce the occurrence of diseases during the cultivation, and also can eliminate some of the crabs with poor constitution.
2. When crabs are caught, they should be stopped and stopped, light traps should be used, crabs should have less impurities, and have strong vitality. Before packing, drain the water and put it evenly when it is put into the box to prevent crabs from crowding together and causing death.
3. Early Miao should choose to transport during the day, late Miao should be transported at night. Sun protection and wind protection during transportation. Motor vehicle transportation, when the car closed the doors and windows, open the doors and windows when parking, ventilation, no smoking in the car, spray water every 2 hours on the way, increase the humidity of the crab seedling box.
4. After the long-distance transportation, the crab seedlings have been basically dehydrated. If they are directly put into water, the crab seedlings tend to produce air bubbles and affect the survival rate. So before the crabs enter the pool, there must be an adaptation process: first open the crab box, sprinkle the crab seedlings for 5 minutes, soak the crab seedlings box and the crab seedlings in the pool water, and then leave the water on the shore and repeat after 15 minutes. Once, finally let the crabs go into the pool slowly.
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Yirun Agricultural Cooperative , https://www.yiruncn.com