What are the key technical points of crab farming?

Since ancient times, crabs have been an extremely delicious food. Let's take a look at the techniques for farming crabs.

1. Pond conditions

Abundant water source, convenient water intake and drainage, good water quality without pollution. Choose clay, sandy soil or sub-sandy soil with good aeration, which is favorable for the growth and reproduction of aquatic plants, benthic insects, snails, mussels, aquatic earthworms and so on. Old ponds must be thoroughly desilted, and it is best that the silt does not exceed 20cm; the pond area should not be too small. The pond water depth should be kept at around 0.6—1.5 m year-round, with varying depths in different places, the shallowest being 10cm. Several earth mounds slightly above the water surface, namely crab islands, can be built in the pond, and aquatic plants can be transplanted on the islands. The pond should not be too steep, and the slope ratio should generally be below 1:1.5; otherwise, river crabs tend to dig burrows, and it is not favorable for them to climb out of the water at night. Artificial caves can also be built.

2. Transplanting aquatic plants

The level of the natural yield of river crabs mainly depends on the amount of aquatic plants and benthic organisms (feed organisms) in the water area. Planting aquatic plants well during the farming process is an indispensable technical measure. In addition to providing food for crabs and supplementing vitamins, planting aquatic plants can also serve the functions of supporting and concealing them during mutual fighting, and is an effective measure for increasing the survival rate of river crabs in each period. In addition, it can absorb harmful ammoniacal nitrogen, carbon dioxide and organic matter in the pond, release oxygen and stabilize water quality. People also often say, “The size of the crab depends on the aquatic plants.” Therefore, for pond farming of river crabs, great effort must be made to plant aquatic plants well. The main types of aquatic plants include duckweed, Azolla, water hyacinth, water lettuce, Hydrilla verticillata, hornwort, Vallisneria and alligator weed, among others. When transplanting, pay attention to disinfection and pest prevention.

3. Anti-escape facilities

Anti-escape facilities mostly use plastic film, and cement boards are also used, depending on individual circumstances.

4. Pond clearing and disinfection

Generally, about half a month before releasing the seedlings, quicklime is used to clear and disinfect the pond, at 75 kg per mu. On the one hand, it can kill harmful organisms, and on the other hand, it can improve the pond bottom, increase the calcium ion content in the water body, and promote the molting and growth of river crabs. After filling with water, fertilize in time to cultivate algae and basic feed, and generally keep the transparency at 40—50cm. If tadpoles or frog eggs are found, remove them in time to avoid competing for food and harming young crabs.

5. Releasing seedlings

For seedling selection, crab seedlings produced in the Yangtze River system are preferred, and they are required to be uniform in size, complete in walking legs, robust in constitution, active in crawling, and free of injuries and diseases.

For seedling release and density, pay attention to temperature differences when releasing seedlings. Seedlings purchased from other places cannot be put directly into the pond. They should first be soaked in water for 2—3 minutes, taken out and left for 10 minutes, and this should be repeated 2—3 times. After the young crabs gradually absorb enough water and adapt to the water temperature, put them into the pond, which can increase the survival rate.

Density: At present, most are mainly mixed culture, especially mixed culture of fish, shrimp and crabs, which brings higher economic benefits. The density can be controlled within 1500 crabs/mu, with juvenile crabs of 120—150 crabs/kg. If the conditions are relatively poor or shrimp farming is the main focus, the amount of seedlings released can be appropriately reduced.

6. Daily management

(1) Feeding: In the whole process of intensive pond culture, it mainly relies on artificial feeding of feed, so the type, quality and quantity of feed have a great influence on the growth and development of river crabs. When feeding, the principle of a reasonable combination of fine, green and coarse feed should be adhered to: animal-based fine feed accounts for 40%, aquatic plants account for 35%, and other plant feed accounts for 25%. The types of feed mainly fall into three major categories: (1) complete formula feed specially for river crabs; (2) animal-based: marine and freshwater small trash fish, various animal carcasses, snails, mussels, livestock and poultry blood, fish meal, silkworm pupae, etc.; (3) plant-based: aquatic plants, duckweed, alligator weed, Vallisneria, Hydrilla verticillata, etc.; commercial feed: sweet potato, potato, grains, bran, rice bran, etc.

Summary: There are many methods for crab farming. If crabs are farmed better and more carefully, they can certainly be raised well, but attention must be paid to the farming methods, so that better economic benefits can be produced.