Key Technical Points and Daily Management Methods for Freshwater Crab Farming

Around the Mid-Autumn Festival is the best time to eat crabs, and just thinking about it makes your mouth water. However, high-quality Chinese mitten crabs are not cheap either. Eating crabs to improve your meals is a good choice, but as everyone's living standards get higher and higher, the pursuit of quality also gets higher and higher, so crab farmers need to pay attention and study farming techniques well. In our daily lives, the most commonly seen are actually freshwater crabs, because compared with other crabs, freshwater crabs are easier to raise in large quantities, and so there are more of them on the market.

Freshwater Crab Farming Techniques

1. Juvenile crab (button crab) cultivation

To increase the survival rate of young crabs and boost economic returns, the first step is to cultivate button crabs. To reach marketable crab size, most use plastic greenhouse temporary holding techniques. Choose a pond with good water quality and ample water supply; the area should not be too large, water depth should not exceed 1.2 m, and an east-west orientation is best, with plenty of sunlight.

1. Stocking seedlings. 15-20 days before stocking crab seedlings, spread 75 kg of quicklime per mu for disinfection. After the lime's effect has dissipated, let water in through an 80-mesh filter screen, cultivate basic bait, transplant aquatic plants (which must be strictly disinfected), and set up necessary escape-prevention facilities. When the crab seedlings enter the pond, the water can be slightly shallow. This helps raise the water temperature and promotes the growth of algae and aquatic plants in the water.

2. Feeding. Feed 2-3 times a day, feeding soybean milk, minced fish, shrimp, etc. When feeding, it is better to place more feed in the shallow areas around the edges. Calculate the feed amount as 4% of body weight, and at any time adjust according to the weather, water conditions, individual growth, and the amount of competing organisms for food. As the young crabs grow, also increase high-quality aquatic plants such as duckweed.

3. Water quality. In daily management, pay attention to regulating water quality. You should keep the water fertile but fresh; when changing water, change it frequently but in small amounts, and do not cause drastic changes in water temperature and water level. After about 2 months of cultivation, they can reach the button crab stage.

2. Adult crab farming

Adult crabs prefer a water environment with clean water quality and relatively high transparency, with dense aquatic plants and abundant bait. This is most suitable for river crab growth. Most use pond, lake, river channel, and rice field farming.

1. Pond conditions

Use a site with ample water supply, convenient water intake and drainage, good water quality without pollution, and choose clay, sandy soil, or sandy loam with good aeration, which is conducive to the growth and reproduction of aquatic plants, benthic insects, snails and mussels, aquatic earthworms, etc. Old ponds must be thoroughly desilted, with the shallowest part at 10 cm. Several earthen 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; the slope ratio is generally below 1:1.5, otherwise river crabs are prone to digging burrows, and it is not conducive to crawling out of the water for activity at night. Artificial caves can also be built.

2. Transplanting aquatic plants

The level of natural river crab yield mainly depends on the amount of aquatic plants and benthic organisms (bait organisms) in the water area. During the farming process, planting aquatic plants well is an indispensable technical measure. Besides providing food for crabs and supplementing vitamins, people also often say, “the size of the crab depends on the aquatic plants.”

3. Escape-prevention facilities

Escape-prevention facilities mostly use plastic film, and some use cement boards, depending on each situation.

4. Pond clearing and disinfection

Generally, half a month before stocking seedlings, use quicklime to clear and disinfect the pond, at 75 kg per mu. On one hand, it can kill harmful organisms; on the other hand, it can improve the pond bottom, increase the calcium ion content in the water, and promote river crab molting and growth. After filling with water, fertilize in time to cultivate algae and basic bait. Transparency should generally be kept at 40-50 cm. If tadpoles or frog eggs are found, remove them in time to avoid competing for food and harming young crabs.

5. Stocking seedlings

For seedling selection, crab seedlings produced in the Yangtze River system are best. They should be uniform in size, have complete walking legs, be strong in constitution, active in crawling, and free of injuries and disease.

For stocking seedlings and density, pay attention to temperature differences when stocking. Seedlings purchased from other places should first be soaked in water for 2-3 minutes, taken out and left for 10 minutes, and this repeated 2-3 times. After the young crabs gradually absorb enough water and adapt to the water temperature, then put them into the pond. This can increase the survival rate.

6. Density: Most use mixed farming, especially mixed farming of fish, shrimp, and crabs, which gives higher economic returns. Density can be controlled within 1500 crabs per mu, with button crabs of 120-150 crabs per unit specification. If conditions are poor or shrimp farming is the main focus, the stocking amount can be appropriately reduced.

The Living Environment of Freshwater Crabs

1. Crabs can attach to wood or other floating objects to live, and many species also live commensally with other animals.

2. A small number of crab species grow and reproduce completely in freshwater, and they mostly inhabit under stones in mountain streams.

3. Cryptochiridae live in the sacs formed by reef-building corals. After the adult female crab mates, she is confined in the sac for life, and the hatched larvae can escape through small openings that have not closed.

4. Pea crabs often sneak into the mantle cavity of some mollusks, or live commensally in the tubes of polychaetes.

5. A few crabs, such as land crabs, can adapt to terrestrial life and burrow in damp mud holes, while migrating to the sea during the breeding period. The vast majority of crabs are omnivorous.

Morphological Characteristics of Freshwater Crabs

Freshwater crabs have a well-developed cephalothorax and a degenerated abdomen, commonly called the “navel.” Males have a pointed navel, and females have a round navel. Just as ink has six shades and the qin has seven notes, crabs also have multiple flavors: crab meat is one flavor, crab paste is one flavor, crab roe is one flavor, and crab seeds are yet another flavor.

Differences Between Freshwater Crabs and Sea Crabs

1. Freshwater crabs have a round back shell, while sea crabs have a spindle-shaped one.

2. Sea crabs can be eaten whether dead or alive, while freshwater crabs can only be eaten alive.

3. Fresh river crabs have glossy shells, strong clamping force in the claws, smooth leg hairs, and complete and firm legs, crawl quickly, and when quiet you can hear their faint sound of bubbling. Before eating freshwater crabs, it is best to keep them in clean water for some time so they spit out the filth in their bellies, then remove the crab stomach and cook them before eating.

4. Freshwater crabs and sea crabs have different market seasons. Sea crabs have a relatively long market period, lasting from April all the way to October. Freshwater crabs come to market later than sea crabs and also have a shorter market period, generally from July to October.

There are many varieties of crabs, and each variety has a different price, different taste, and different farming techniques. Everyone needs to study well what issues to pay attention to when farming crabs. Therefore, farmers should decide which variety to farm according to the market in order to maximize profits.