A Detailed Explanation of the Latest Scientific River Crab Farming Techniques

Along with the rapid development of the domestic economy, the specialty farming industry has gradually risen, and the people's living standards and consumption levels have gradually improved, so some seafood products have slowly appeared on the dining table, so farming river crabs has great economic value. Mastering river crab farming techniques is crucial for farmers to get rich. Now follow the editor to learn about it together:

The Latest Scientific River Crab Farming Techniques

Pond Conditions

Sufficient water source, convenient water intake and drainage, good water quality with no pollution. Choose clay, sandy soil, or loamy sand, which has good aeration and is conducive to the growth and reproduction of aquatic plants, benthic insects, snails and mussels, aquatic earthworms, etc. Old ponds must be thoroughly desilted, and it is best that the silt does not exceed 500px. The pond area should not be too small. The pond water depth should be maintained at around 0.6-1.5 m year-round, with varying depths in different places, the shallowest being 250px. Several earthen mounds slightly above the water surface, namely crab islands, can be built in the pond, and aquatic plants can be transplanted onto the islands. The pond should not be too steep, and the slope ratio should generally be above 1:1.5; otherwise, river crabs are prone to burrowing, and it is not conducive to them climbing out of the water to move about at night. Artificial caves can also be built.

Transplanting Aquatic Plants

In the farming process, planting aquatic plants well is an indispensable technical measure. Besides providing food for the crabs and supplementing vitamins, planting aquatic plants can also reduce mutual fighting and provide concealment. It is an effective measure for increasing the survival rate of river crabs in each period. In addition, it can absorb harmful ammonia nitrogen, carbon dioxide, and organic matter in the pond and release oxygen, stabilizing water quality. The main types of aquatic plants include duckweed, Azolla, water hyacinth, water lettuce, Hydrilla verticillata, hornwort, Vallisneria, and alligator weed. When transplanting, pay attention to disinfection and pest prevention.

Pond Clearing and Disinfection

Generally, half a month before releasing the seedlings, quicklime is used to clear and disinfect the pond, with a dosage of 50-75 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 it is advisable to keep the transparency at 40-1250px. If tadpoles or frog eggs are found, remove them in time to avoid competing for food and harming young crabs.

Seedling Selection: Crab seedlings produced in the Yangtze River system are preferred, requiring uniform specifications, complete walking legs, strong physique, active crawling, and no injuries or diseases. Seedling release and density: Pay attention to the temperature difference when releasing seedlings. Seedlings purchased from other places cannot be directly put 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. The density can be controlled within 1500 crabs per mu, with a specification of 120-150 juvenile crabs. If conditions are poor or shrimp farming is the main focus, the amount of seedlings released can be appropriately reduced.

Living Habits of River Crabs

Burrowing

River crabs like to live in caves on muddy banks or tidal flats of rivers and lakes, or hide among gravel and aquatic plants. Burrowing is an instinct of river crabs and also an adaptive way for them to defend against enemies. River crabs generally choose hard-soiled steep banks for burrowing, with a bank slope of 1:0.2 or 1:0.3. They rarely build burrows on gentle slopes below 1:1.5-2.5, and even less on flat ground. This provides a basis for the construction of our farming ponds.

Feeding Habits

River crabs have very omnivorous feeding habits. Under natural conditions, they mainly feed on aquatic plants and humus, are fond of animal carcasses, and also like to eat snails and mussels, worms, and insects. Occasionally they also prey on small fish and shrimp. When food is scarce, they will even cannibalize one another, and may even swallow the eggs they carry themselves. Sometimes a dead fish will cause同类 to compete for food. Under normal circumstances, it is easy for river crabs to obtain plant-based food, which often constitutes the main component of the crab's stomach contents. There is also some mud and sand in the crab's stomach, which is a sign that river crabs feed on benthic organisms and humus.

River crabs generally hide in caves during the day and come out at night to seek food. On land, river crabs do not eat much; they often drag food from the shore to underwater or to the edge of the cave before eating. Throughout the year, except when they lie dormant in low temperatures and temporarily do not feed, river crabs feed as usual even during winter migration. When water quality is good, water temperature is suitable, and bait is abundant, river crabs eat a great deal and can continuously prey on several snails in a day and night. Newly molted soft-shell crabs and individuals with damaged limbs often suffer attacks. However, river crabs also have a strong ability to endure hunger; after 10 days or even half a month without food, river crabs will not starve to death. Under artificial farming conditions, according to the needs of river crab growth and development, in feeding bait, grasping the “fine—coarse—fine” structure is beneficial to the growth of river crabs.

Daily Management of River Crabs

1. Feeding: In the entire process of intensive pond farming, it mainly relies on artificial feeding of feed, so the type, quality, and quantity of feed have a great impact on the growth and development of river crabs. When feeding, adhere to the principle of a reasonable combination of fine, green, and coarse materials. Animal-based fine feed accounts for 40%, aquatic plants account for 35%, and other plant feed accounts for 25%. There are mainly three major categories of feed: (1) complete special compound feed 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 types: sweet potato, potato, grains, bran, rice bran, etc.  

2. Water quality management: River crabs have higher requirements for water quality conditions than fish, and are especially more sensitive to polluted water bodies. Good pond water quality is conducive to the growth and development of river crabs and gives them a delicious meat flavor. The pH value of crab pond water should be maintained at 7-9, with the optimum being 7.5-8.5. The dissolved oxygen in pond water should be maintained above 5mg/L; below 5mg/L will affect growth, and below 2mg/L will cause death of river crabs. To adjust the pH value of pond water: newly excavated ponds mostly have acidic water quality, so quicklime slurry should be regularly splashed to improve water quality. This can improve the utilization rate of feed by river crabs and help them molt smoothly. Generally, once a month in spring, and once every 15-20 days in summer and autumn, using 7-10 kg of quicklime per mu at a water depth of 1 m.

3. Anti-escape: Have dedicated personnel on duty patrolling the embankment, especially on rainy days and when changing water.

4. Pond patrol: Observe the water color, pay attention to crab activity, do not injure the river crabs, and keep the water environment stable. When the gonads are plump and the price is suitable, drain the pond water and pick them up.

Disease Prevention and Control in River Crab Farming

In recent years, with the continuous expansion of crab farming scale, crab diseases have also continued to spread and escalate. Crab diseases that never existed before now also occur in large numbers, mainly ciliate disease in young crabs and trembling disease in adult crabs, bringing huge economic losses to the crab farming industry. Therefore, crab disease prevention and control should adhere to prevention first, achieve early discovery and early treatment, prevent disease before it occurs, and treat disease early when it occurs, adopting different methods for prevention at different growth stages. Use microbial preparations such as photosynthetic bacteria and EM bacteria to regulate water quality. In high-temperature seasons, regularly use quicklime, dibromohydantoin, etc. for prevention. During the high-incidence period of ciliates, use crustacean cleaner or ciliate cleaner and other insecticides once every 15—20d. To avoid drug resistance, drugs should be used alternately. Trembling disease is a microorganism between bacteria and viruses. Using decamethrin to clear the pond is an effective method for preventing and controlling trembling disease.

When farming river crabs, from the moment of choosing the farming site, you must put in sufficient effort; otherwise, in later cultivation, due to insufficient earlier work, the growth of river crabs will be poor, and by then solving it will be of no help. So when farming river crabs, you must never be careless.