From February to February this year, we conducted a trial to cultivate large-scale young crabs in greenhouses. As a result of the test, the seedling period was 75 days, and the overall survival rate was 50%. The average weight of the larvae was 3.2 g and the maximum larvae was 11.8 g. It is not only technically feasible, but also very economical.
(a) Greenhouse conditions. The test greenhouse is a double steel solar greenhouse with an area of ​​1200 square meters (2060) and a nursery water body area of ​​1,000 square meters. With inflatable aeration facilities and pipeline heating equipment, the light transmittance in the greenhouse is about 50%, and 5 incandescent lamps of 200 watts are installed for night lighting. In order to feed the feed easily and uniformly, 3 sidewalks are provided.
(b) Preparation before laying seedlings. About 10 days before the emergence of the seedlings, 30 cm of water was discharged and strictly disinfected with a quicklime emulsion of 100 ppm. After 24 hours of disinfection, the oxygenation facility was started to oxygenate. Next, the aquatic plants were placed, and the plants were mainly water peanuts. The watered grasses were soaked in high-concentration lime water or potassium permanganate solution for 24 hours, then rinsed with clean water and evenly placed in the greenhouse. Aquatic grasses cover about 80% of the water area. Then gradually warm the water to 20-22 °C.
(iii) Stocking of crabs. On February 10th, 3 kg of Eriocheir sinensis big eye larvae were purchased from Rudong County, Jiangsu Province, with a specification of 140,000/kg, and desalinated for 5 days. Due to the dry transport, it is easy to cause dehydration of the
Crab seedlings. After the crab seedlings reach the greenhouse, they cannot directly enter the pool. They should first put the crab seedlings into the water, soak for 30 seconds, and then take out the water for about 5 minutes. , And then into the water for 30 seconds, so repeat 4-5 times and then put the seedlings. Choose a place where there is no water grass, gently grab a small seedling, slowly shake, so that the crab seed can be evenly dispersed into the water. Although after 3 hours of transport, bigeye larvae almost died.
(D) Daily feeding and management. When the crabs enter the pool, they are mainly fed with tofu,
Fish paste, and adult insects such as aphids. The tofu was filtered into tiny particles using a 40-mesh mesh, and then poured evenly over the whole pool. After cleaning the small fish and using a beater to beat the fish slurry, add the salt to the whole water and spread it evenly. The daily bait rate is 100%-150%, and it is fed 4 times a day, ie before dawn, at noon, in the evening and at midnight, and the light is turned on for 2-3 hours when feeding at midnight. When the crabs basically reach the stage II juvenile crab, the bait is mainly bean cake and fish paste, and occasionally feeding 1-2 times of tofu. After the bean cake is cooked, it is still made into small pieces. At this time, the bait rate is controlled at about 100%, and the feeding is still performed 4 times a day. Gradually add water to 0.5 meters during this period. After the V period, the bait rate was 60%-80%, and the bait was still dominated by bean cakes and small fish. Feeding was done 3 times a day and no investment was made at midnight. During the whole period of raising the seedlings, observe the activities and feeding conditions of the crabs, estimate the number and importance of the crabs in the pond, and determine a reasonable amount of feeding. During the concentration of clam shells, the amount of bait may be appropriately reduced, and the turn-on time may be increased at night.
The daily management work is mainly to control the water quality and regular disinfection. Weekly use 5ppm lime emulsion to water evenly on the whole pool, add some calcium, keep the pH value of 7.5-8.5; disinfect with 50% stable chlorine dioxide 0.5ppm once every 10 days, change the water once every 15 days The amount of water to be changed is about 30%, and some new water is added appropriately. The water level is controlled at about 0.5 meters. When changing the water, the inlet and outlet shall be wrapped with 80-mesh sieve to prevent the seedlings from being discharged or other harmful organisms. Note that the temperature difference is within 5°C, and the best water temperature is basically the same. Usually pay attention to the growth of aquatic plants in the pond, and timely add some fresh plants.
(e) To nurture results. By April 26, the water temperature in Outer Pond had reached about 14°C and began to sprout. By May 8, it had emerged seven times and a total of 174,000 baby crabs were provided, providing large-sized young crabs for 180 acres of crab ponds.
In short, the key technology to cultivate large-sized juvenile crabs in greenhouses is to select good seedlings, determine the reasonable stocking density, and strengthen daily management.
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