With the development of aquaculture, in addition to the renewal of cultured species, aquaculture specifications have a direct impact on the economic benefits of aquaculture. To develop a large-sized porthole crab, in addition to the daily management such as feeding and changing water, extending the growth period is also an important measure. It requires the early release of seedlings as soon as possible. In the past few years, the use of sea-raised crabs for raising crabs in the Shandong area was mostly in late May to early June. In recent years, if water temperatures in spring are high, the crabs can grow if they can advance to the end of April to early May. The period can be extended by 15 days to 30 days. Therefore, we have carried out a greenhouse cultivation for the crabs that were caught in the fall and succeeded.
First, site selection Choose rich underground water, good fresh water resources, and build sheds where the leewards are sunny.
Second, the greenhouse structure is a brick wall, plastic film roof, structure and vegetable greenhouse similar. The greenhouse has a practical area of ​​600 square meters. A total of 20 wintering ponds are designed. Each pond has an area of ​​30 square meters, a water depth of 50cm, and a sediment thickness of lOcm-12cm at the bottom of the pool. A fountain-type water change is used. The drain outlet is inserted with a PVC pipe that is 5 cm below the wall of the pool to facilitate overflowing. Each pool is equipped with a 25mm PVC tube coiled, and a small hole is drilled every 20cm on the PVC pipe. When water enters, water is ejected from the small hole, such as a fountain, so that it can change the water and increase oxygen. .
Third, the sand cement pool should be cleaned first and then sanded with 10ppm potassium permanganate for 30 minutes. Sand thickness 10cm --- 12cm, use fine sand and sifting, sieve out the larger chunks in the sand, and clean and disinfect the sand.
The specific method is: Wash the sand with clean water, wash away dirt and other impurities, use 10ppm potassium permanganate disinfection for 10 minutes, then rinse, and then the disinfected sand paving pool, sand at the outlet Leave a lm wide feeding area.
Fourth, the pro-crab selection room From the beginning of October, we purchased sea-racing crabs from fishing boats. After strict selection, the disinfection room was used as a winter pro-crab. Selection criteria: pure breeds, complete appendages, no internal or external injuries, strong vitality, good fullness, firm abdomen, tightened, individual weight over 200g. Pro-crab disinfection: The selected crabs were sterilized with 300 ppm formaldehyde for 20 minutes, and then rinsed to leave the wintering pool.
5. Water Treatment In order to avoid diseases caused by seawater pollution and reduce the survival rate of overwintering, we use underground brine plus freshwater deployment as the wintering water for the crab. The process flow is as follows:
Underground brine extraction → Exposure → Add fresh water to regulate salinity → Ion component tests → Determine overwinter water formula → Ion content regulation → Stir → Resting → Standby.
Sixth, the density of wintering in order to improve the survival rate, stocking density of 6 / square meter -8 / square meter is appropriate.
VII. After daily management of the selected crab house, enter daily management work. The specific contents include:
1. Feeding: Feeding once a day, feeding in the evening. From the human room to the water temperature dropped to 8 °C, mainly feeding sandworms, small fish and other bait, the amount of bait according to the weight of 3% -1% gradually decreasing, and timely inspection of the bait situation, adjust the amount of feeding; In spring, when the water temperature rises to above 12°C, the crabs begin to feed and feed, but this time the food intake is small and they can feed a small amount. As the water temperature rises, the food intake of the shuttle crab gradually increases and the amount of feed increases. Large, pay attention to observing the residual bait and adjust the feeding amount in time. Baits are mainly low-value shellfish such as cocoons and horned oysters.
2. Change the water: Change the water every 2 days to 3 days during the feeding period. In the winter when the water temperature is lower than 80°C, the water is changed once every 5 days - 7 days. When the water is changed, the residual bait is cleaned and the dead crab is taken out.
3. Temperature regulation: Measure the water temperature once every morning, afternoon and evening, and make a record. The temperature control in winter is between 3°C and 5°C. Due to the greenhouse wintering, the insulation performance is good. When the weather is good, the indoor air temperature is high and can reach l2°C or above. At this time, the ventilation window can be opened for ventilation and cooling, cloudy (snow) days or When the cold current comes, in addition to covering the straw curtain at the roof, if necessary, a small stove can be raised in the shed to increase the temperature, so as to ensure that the water temperature does not fall too fast. From the beginning of February, the temperature rises slowly, and the temperature rises by 0.2°C per day. From 5°C to early March, it rises to 12°C-15°C. At this time, the accumulated temperature has reached 2000°C and some individuals hold eggs.
4. Pick eggs and crabs: After the pro-crabs hold the eggs, pick eggs and crabs in separate ponds every day. After 3 days and 5 days of incubation, you can directly move to the human nursery room to grow eggs.
5. Disinfection: During the winter, despite the use of underground brines to overwinter, bacterial and other micro-organisms and certain protozoa still have an impact on broodstock. Therefore, it is necessary to sterilize the pro-crabs during wintering. Generally, the water temperature is disinfected once per week above 10°C, and the water temperature is disinfected once every 15 days to 20 days below 10°C. The disinfection method is: Disinfect with 100ppm formaldehyde for 30 minutes or 5ppm potassium permanganate for 10 minutes.
VIII. As a result, in the 600 m2 greenhouse, a total of 4,538 crabs were raised during the wintering period. By March 16th, a total of 3365 portate crabs held their eggs. Of these, 705 died during the wintering process, and 468 were unoccupied (possibly unmated). Only the winter survival rate was 84.5%, the egg holding rate was 87.8%, and the egg holding capacity was between 600,000 and 800,000 tablets. The overwintering pro-crabs have a high accumulated temperature in winter and hold their eggs early. In early April, hatching and nursery are already available. By the end of April and early May, young crabs of Phase II can be cultivated. This is approximately one less than that of crabs reared with sea crabs. month.
IX. Issues Worth Discussing
1. The survival rate and the rate of holding eggs of winter crab are one of the issues worth discussing.
2. The density of overwintering density, and its relationship with winter survival rate and holding rate are the second issues worth discussing.
First, site selection Choose rich underground water, good fresh water resources, and build sheds where the leewards are sunny.
Second, the greenhouse structure is a brick wall, plastic film roof, structure and vegetable greenhouse similar. The greenhouse has a practical area of ​​600 square meters. A total of 20 wintering ponds are designed. Each pond has an area of ​​30 square meters, a water depth of 50cm, and a sediment thickness of lOcm-12cm at the bottom of the pool. A fountain-type water change is used. The drain outlet is inserted with a PVC pipe that is 5 cm below the wall of the pool to facilitate overflowing. Each pool is equipped with a 25mm PVC tube coiled, and a small hole is drilled every 20cm on the PVC pipe. When water enters, water is ejected from the small hole, such as a fountain, so that it can change the water and increase oxygen. .
Third, the sand cement pool should be cleaned first and then sanded with 10ppm potassium permanganate for 30 minutes. Sand thickness 10cm --- 12cm, use fine sand and sifting, sieve out the larger chunks in the sand, and clean and disinfect the sand.
The specific method is: Wash the sand with clean water, wash away dirt and other impurities, use 10ppm potassium permanganate disinfection for 10 minutes, then rinse, and then the disinfected sand paving pool, sand at the outlet Leave a lm wide feeding area.
Fourth, the pro-crab selection room From the beginning of October, we purchased sea-racing crabs from fishing boats. After strict selection, the disinfection room was used as a winter pro-crab. Selection criteria: pure breeds, complete appendages, no internal or external injuries, strong vitality, good fullness, firm abdomen, tightened, individual weight over 200g. Pro-crab disinfection: The selected crabs were sterilized with 300 ppm formaldehyde for 20 minutes, and then rinsed to leave the wintering pool.
5. Water Treatment In order to avoid diseases caused by seawater pollution and reduce the survival rate of overwintering, we use underground brine plus freshwater deployment as the wintering water for the crab. The process flow is as follows:
Underground brine extraction → Exposure → Add fresh water to regulate salinity → Ion component tests → Determine overwinter water formula → Ion content regulation → Stir → Resting → Standby.
Sixth, the density of wintering in order to improve the survival rate, stocking density of 6 / square meter -8 / square meter is appropriate.
VII. After daily management of the selected crab house, enter daily management work. The specific contents include:
1. Feeding: Feeding once a day, feeding in the evening. From the human room to the water temperature dropped to 8 °C, mainly feeding sandworms, small fish and other bait, the amount of bait according to the weight of 3% -1% gradually decreasing, and timely inspection of the bait situation, adjust the amount of feeding; In spring, when the water temperature rises to above 12°C, the crabs begin to feed and feed, but this time the food intake is small and they can feed a small amount. As the water temperature rises, the food intake of the shuttle crab gradually increases and the amount of feed increases. Large, pay attention to observing the residual bait and adjust the feeding amount in time. Baits are mainly low-value shellfish such as cocoons and horned oysters.
2. Change the water: Change the water every 2 days to 3 days during the feeding period. In the winter when the water temperature is lower than 80°C, the water is changed once every 5 days - 7 days. When the water is changed, the residual bait is cleaned and the dead crab is taken out.
3. Temperature regulation: Measure the water temperature once every morning, afternoon and evening, and make a record. The temperature control in winter is between 3°C and 5°C. Due to the greenhouse wintering, the insulation performance is good. When the weather is good, the indoor air temperature is high and can reach l2°C or above. At this time, the ventilation window can be opened for ventilation and cooling, cloudy (snow) days or When the cold current comes, in addition to covering the straw curtain at the roof, if necessary, a small stove can be raised in the shed to increase the temperature, so as to ensure that the water temperature does not fall too fast. From the beginning of February, the temperature rises slowly, and the temperature rises by 0.2°C per day. From 5°C to early March, it rises to 12°C-15°C. At this time, the accumulated temperature has reached 2000°C and some individuals hold eggs.
4. Pick eggs and crabs: After the pro-crabs hold the eggs, pick eggs and crabs in separate ponds every day. After 3 days and 5 days of incubation, you can directly move to the human nursery room to grow eggs.
5. Disinfection: During the winter, despite the use of underground brines to overwinter, bacterial and other micro-organisms and certain protozoa still have an impact on broodstock. Therefore, it is necessary to sterilize the pro-crabs during wintering. Generally, the water temperature is disinfected once per week above 10°C, and the water temperature is disinfected once every 15 days to 20 days below 10°C. The disinfection method is: Disinfect with 100ppm formaldehyde for 30 minutes or 5ppm potassium permanganate for 10 minutes.
VIII. As a result, in the 600 m2 greenhouse, a total of 4,538 crabs were raised during the wintering period. By March 16th, a total of 3365 portate crabs held their eggs. Of these, 705 died during the wintering process, and 468 were unoccupied (possibly unmated). Only the winter survival rate was 84.5%, the egg holding rate was 87.8%, and the egg holding capacity was between 600,000 and 800,000 tablets. The overwintering pro-crabs have a high accumulated temperature in winter and hold their eggs early. In early April, hatching and nursery are already available. By the end of April and early May, young crabs of Phase II can be cultivated. This is approximately one less than that of crabs reared with sea crabs. month.
IX. Issues Worth Discussing
1. The survival rate and the rate of holding eggs of winter crab are one of the issues worth discussing.
2. The density of overwintering density, and its relationship with winter survival rate and holding rate are the second issues worth discussing.