Breeding methods of River Crab in soil Pond

1. Crab breeding in soil pond refers to the method of artificially cultivating crab larvae in excavated ponds by using natural seawater in coastal areas. This method is low cost, simple and practical, suitable for crab professional households to adopt. In addition to the cultivation pool, crab seedlings in earthen ponds should also have parent crab ponds, pro-production ponds, bait ponds, seawater sedimentation tanks and other equipment. As long as the salinity is above 0.013 in the pollution-free seawater area, the pond can be built to breed crab. Its breeding conditions are closer to natural ecology. General pond crab breeding in the wild, to prevent the invasion of cold air caused by water temperature drop, conditions can be taken warm facilities. Or seedling time back later, if the water temperature is relatively stable, seedling survival rate can also be greatly improved.

Second, the pond structure requires that the pond shape should be square, the area should be 0.5~1 mu, the water depth should be 1.5 meters, because the larvae like to cluster, like the wind countercurrent, like the corner and other habits, so most of the seedlings in the cultivation pond are concentrated at the upwind end of the pond. If the pool area is too large, most of the seedlings concentrated together, easy to cause local areas crab seedlings too dense, causing lack of bait, hypoxia and so on and a large number of deaths. Sand should be used at the bottom of the pool, and stone (or cement prefabricated board) should be used around the pool to form stone walls (or cement walls), so that the larvae will not be stranded and dry when the water level changes. One end of the pool is provided with a water inlet valve. and the other end is provided with a trumpet-shaped bottom outlet. The outlet hole of the trumpet is blocked with GG54 nylon screen or polyethylene cloth to prevent larvae from escaping when the pool water is pumped. Third, pond cleaning and disinfection is generally carried out 10 to 15 days before larval cultivation to kill harmful organisms (fish, shrimp, aquatic insects, etc.), remove sewage from the pool, remove sludge at the bottom of the pool, wash the pool wall, maintain drainage pipes, etc. Clear pool drugs are quicklime, bleaching powder, formalin, malachite green and so on. (1) Quicklime: When using, drain the pool water to 10~20 cm, evenly put quicklime, sprinkle the whole pool, the dosage per mu is 75~100 kg, and 7~10 days after clearing the pool can be used. (2) bleaching powder: Because bleaching powder is very volatile and decomposed in the air, after taking out the bleaching powder, it should be poured into the wooden barrel immediately, mixed with water into paste, and then diluted with water. If there is no water in the pool, the dosage is 6~10 kg per mu. Clear the pond with water, and apply 100g per cubic meter of water. Bleached pond cleaning was carried out 4~6 days before hatchling. (3) Formalin: Good effect on killing viruses and protozoa in the pool. In the case of dry ponds, 6~10 kg of formalin is used per mu for construction. Sprinkling in the whole pond has killing effect on pygmy worm, and the application should be carried out 10 days before larval cultivation. (4) malachite green: clear the pond with water, so that the concentration of malachite green solution in the pond water reaches 0.25~0.4ppm, which has significant effect on killing seawater plankton such as copepods. Apply it half a month before seedling. (5) Trichlorfon: It is a broad-spectrum organophosphorus insecticide. Among them dichlorvos has a strong stomach poison and killing effect on insects. 0.25ppm concentration has remarkable effect on killing cladoceras in water. Apply pesticide half a month before seedling. 4. Inflow and Fertilization The seedling water is filtered by sieve silk, disinfected by bleaching powder of 50~100ppm, and then precipitated twice in 7 days. It is filtered by sieve silk of 120 mesh and 80 mesh and injected into the pool. Then fertilizer is applied once a day, and the fertilizer application amount is potassium nitrate 5ppm and potassium dihydrogen phosphate 0.5ppm. When the water color is light tea color, potassium nitrate 2ppm and potassium dihydrogen phosphate 0.2~0.3ppm are applied every day. If the content of copper and zinc in the water exceeds the water quality standard, 3ppm EDTA should be added. 5. feeding 1 - 1.5kg calcium nitrate per mu 4 - 5 days before crab larvae hatch, and inoculating pre-cultured single-cell algae solution into the pool. Once hatched, they can feed on unicellular algae. In case of cloudy days, algae reproduction is not good, available 1~1.5 kg per mu cooked soybean milk sprinkle fertilizer. When the zoea larvae entered the second stage, they began to feed on rotifers and small nauplii of meatid insects. During the period from the fourth stage of zoea to megalopa, the nauplii of the megalopa are fed daily, and the density of the nauplii is more than twice that of the mitten crab larvae, so as to ensure sufficient food base.