Detailed guide to box crab farming: you can raise crabs well even in boxes

Crabs are in great demand in daily life. Many people like eating crabs, and crabs have high nutritional value, as they are rich in protein, so many people enjoy them. However, crabs are considered a cooling food, so the editor reminds everyone that although crabs are tasty, you should not overindulge.

Pond conditions and facilities for crab farming  

Based on the living habits of river crabs, the crab pond needs to meet the following conditions:  

① Moderate area, generally 3500 sq m to 6670 sq m.  

② The pond is rectangular and oriented east-west, with a slope ratio of 1:2.5 to 3, a water depth of 1 m to 1.5 m, strong water retention, and no seepage.  

③ The soil is clay loam, and the bottom silt must not be too thick, so as not to hinder the river crabs from burrowing.  

④ The environment is quiet; even slight disturbance will affect the river crabs' feeding and molting.  

⑤ Along the foot of the slope around the crab pond, at 2 m to 3 m, dig a ring-shaped crab-collecting ditch 4 m to 6 m wide and 0.6 m to 1 m deep; the slope foot edge and the middle are large platforms, or dig a crab-collecting ditch in the middle of the crab pond, with large platforms on both sides of the ditch.  

⑥ Plant aquatic plants such as alligator weed and water hyacinth in the crab pond, with the planting area accounting for 1/5 of the crab pond; plant tape grass, hydrilla, and similar plants on the pond bottom to simulate a natural ecological environment.  

Escape-prevention facilities for crab ponds mostly use polyethylene mesh enclosure. Place 3×3 polyethylene mesh (with a mesh size such that crabs cannot escape) on the pond ridge, with the net 1 m high, buried 0.2 m in the soil, 0.5 m above ground, and another 0.3 m used as a cover net, inclined at 45 degrees to the wall net, then tie 0.3 m wide plastic film to the cover net.  

Seed crab selection and stocking  

Seed crabs should preferably be high-quality Yangtze River crab seeds with relatively fast growth, strong physique, complete limbs, intact shells, active crawling, uniform size, and no injuries or diseases. The stocking time is from December to March of the following year, and the suitable size is 80 to 120 crabs per kg, with 15 kg to 20 kg, or 1200 to 1600 crabs, stocked per 667 sq m. 15 to 20 days before stocking, dissolve 60 kg to 80 kg of quicklime per 667 sq m and splash it over the whole pond for pond clearing and disinfection. After the toxicity disappears, apply 800 kg to 1000 kg of fermented livestock and poultry manure per 667 sq m, and add fresh water to fertilize the water quality. When stocking, soak the seed crabs in 0.0002‰ malachite green or 3% to 4% salt water for 3 to 5 minutes. If the seed crabs are purchased from other places over long distances, they should first be soaked in fresh fresh water for 1 minute, taken out and left for 5 minutes, then soaked again for 1 minute, repeating this two or three times, so that the seed crabs slowly absorb water and the foam is rinsed off, then disinfect and stock.  

Stocking should be done on clear, warm days. Place the seed crabs evenly on the pond edges around the crab pond and let them slowly crawl into the water. Never pour them directly into the pond in piles. Handle them gently during stocking so that the seed crabs are evenly distributed in the pond, to improve the survival rate of stocking. At the same time, fierce fish and bottom-feeding fish such as carp and crucian carp must not be mixed in the crab pond, because river crabs mainly grow by molting, and newly molted river crabs are like tender meat and are easily harmed by swallowing fish. Therefore, only an appropriate amount of upper-layer filter-feeding fish (such as silver carp and bighead carp) can be mixed in the crab pond.  

Feeding river crabs  

River crabs are omnivorous aquatic animals, and the feed given must be fresh. Generally, feed once every day around evening. Feed is placed in shallow water at the pond edge, with multiple feeding platforms set up. When the water temperature is above 10°C, feeding should begin. The daily feeding amount as a proportion of river crab body weight is: 1% in March to April, 5% to 8% in May to July, and more than 10% in August to October. Feeding should be timed, located, qualitative, and quantitative. Generally, every 1 kg of commercial crabs produced requires 3 kg to 4 kg of animal feed (wet weight) and 2 kg to 3 kg of commercial feed. In addition, the annual feed distribution proportion is: animal feed 40%, bran and cake types 25%, green feed 35%.  

Daily management and disease prevention  

1. Pond patrol inspection. Persist in patrolling the pond every morning and evening, observe the feeding and growth of river crabs, check whether there are holes in the pond ridge or blocking nets, and whether the escape-prevention facilities and the mesh covers at the water inlet and outlet are damaged, to prevent crab escape and invasion by enemies.  

2. Water quality management. River crabs have relatively high water quality requirements: dissolved oxygen above 4 mg per L, pH 6.8 to 8.7, and transparency of about 40 cm. In spring, to raise water temperature and promote growth, the water level can be controlled at 0.6 m to 0.8 m; in summer and autumn, when water temperature rises, the pond water depth should be kept at 1 m to 1.5 m. At the same time, change water frequently: once every 7 days in spring, and once every 2 to 3 days in the high-temperature seasons of summer and autumn. Each water change should be 1/3 of the pond water, draining and filling at the same time, so that the water temperature difference is controlled within 3°C. If most river crabs are found climbing ashore, spitting bubbles, and breathing oxygen from the air, especially if a large number of river crabs climb out of the water during the day and do not go down even when startled, or go down and immediately come ashore again, it indicates that the water quality has deteriorated or there is severe oxygen deficiency. At this time, the old water should be quickly replaced. In addition, quicklime should be regularly dissolved and splashed over the whole pond to improve water quality, increase calcium, and promote river crab growth and smooth molting. Generally, at a water depth of 1 m, use 15 kg to 20 kg of quicklime per 667 sq m each time, applying once a month in spring and once every half month in summer and autumn.  

3. Disease prevention and control. In high-temperature seasons, various diseases of river crabs are easily triggered. Persist in prevention being more important than treatment, supplemented by drug prevention and control. Regularly and alternately splash drugs such as 0.001‰ oxytetracycline powder, 0.0005‰ to 0.001‰ furazolidone, and 0.0005‰ Xie'anling. Frequently feed medicated bait: mix 0.1 g to 0.2 g of oxytetracycline or erythromycin per kg of crab weight into the bait and feed. Add an appropriate amount of shell powder, bone meal, fish meal, poultry eggshell powder, molting hormone, and similar substances to the feed to increase calcium, iron, and other elements in the feed, so as to facilitate river crab molting. For parasites, 0.005‰ to 0.01‰ formalin or other appropriate amount of insecticide can be splashed over the whole pond; for bacterial diseases, use bactericidal drugs to disinfect and sterilize the water body two or three times. Combining whole-pond drug splashing with feeding medicated bait gives better results. 

When talking about crabs, everyone may first think of Yangcheng Lake crabs, because Yangcheng Lake crabs are mainly famous for having a lot of crab roe. Therefore, to raise crabs with a lot of crab roe, this is related to the water area and region of farming, so building a good crab pond is very important.