Experience in Culture and Management of River Crab in North China

Eriocheir sinensis, the scientific name of the Chinese mitten crab, has delicious meat, rich nutrition, and has a certain medicinal value, the domestic market demand is large, the economic benefit is considerable, and the breeding prospect is broad. But we all know that the weather in the north will be much colder in winter than in the south, so how to raise crabs in the north?

Experience in Culture and Management of River Crab in North China

First, seedling selection and purchase: at present, the river crab seedlings of the Yangtze River system are better in China, but the river crab seedlings of Liaohe River system and Zhejiang River system are not suitable for introduction and breeding. In addition, the seedlings must go through strict quarantine, can not introduce sick river crab breeding.

Second, culture methods: at present, river crab culture mainly adopts two methods: pond culture and rice field culture.

1. Intensive farming in ponds

Selection and reconstruction of ① ponds: the river crab aquaculture waters require fresh water quality, stable water level, no pollution, high transparency and dissolved oxygen, convenient drainage and irrigation, and rich in aquatic animals such as aquatic plants and snails.

② stocking: after 15 days of pond cleaning and disinfection, choose to release seedlings on rainy days or when the temperature is low every morning or evening. Stocking density: 2-year-old young crabs (individual weight 5 grams), 2000 million per 667 square meters (1 mu); stocking crab seedlings, 0.8 million kilograms per 667 square meters. The right amount of silver carp and bighead carp can be released at the same time.

③ feeding and management: artificial formula feed is fed. At present, special formula feed with crude protein content of more than 35% is used in various places, and it can also be fed with animal feed such as fish, silkworm pupa, earthworms, snail clam meat, slaughterhouse scraps or other animal carcasses. Properly feed aquatic plants, vegetables, grain, rice bran, wheat bran and other plant feed. The feed should be fresh, non-moldy and nutritionally balanced. When feeding, put the feed on the slope or shallow water close to the water level line, setting up 3-5 feeding sites every 667 square meters, feeding once every evening, the feeding amount is 3% and 5% of the body weight. Adjust the feeding amount according to the food intake of the previous day.

2. Raising crabs in rice fields

① field selection: choose fields with sufficient water source, good water quality, no pollution, convenient drainage and irrigation, and strong water retention. Rice planting requirements: select varieties with good rice quality, small leaf opening angle, hard stem, strong fertilizer tolerance, lodging resistance and disease resistance.

② crab fry stocking: 15 days before stocking, remove silt and sundries, disinfect with quicklime and tea bran, 150g quicklime and 50g tea bran per square meter, first sprinkle quicklime, and then sprinkle tea bran soaked for 24 hours on the second day.

③ feeding and management: crab seedlings should be fed immediately after they are put into the field. Mixed with small fish or clam meat with bean cake and wheat bran, it can also be fed with compound feed or slaughtered scraps and other animal feed. Daily feed intake depends on food intake, generally 3% of the total body weight, once a day, in the evening. In general, crab paddy fields should be kept at a depth of more than 30 centimeters, and the water level should be deepened in the high temperature season; the water should be changed every 15 to 20 days to keep the water fresh; make regular inspections, deal with problems in time, and do a good job in preventing escape, theft, and enemy damage.

Points for attention in crab culture

1. Choose and buy high-quality crab seedlings

The quality of crab seedlings determines the quality of adult crabs. Do not buy cheap crab seedlings from improper channels for breeding! You know, in doing so, the ultimate victim is the crab breeders themselves!

2. Prevent precocious puberty of river crab

Precocious puberty of river crabs will lead to a decline in the quality and income of adult crabs. The main causes of precocious puberty of river crabs are poor quality of crab seedlings, excessive feeding and poor water quality. Preventive measures are:

① controls the feeding quantity and quality.

② controls stocking density.

③ controls water quality and water temperature.

3. Pay attention to the regulation of water quality and reduce the cave dwelling of river crabs.

Choose a quiet, adequate water source, good water quality, transparency of 30cm to 40cm, no pollution, suitable water temperature for breeding. The water body of crab culture is composed of deep and shallow parts, and aquatic plants are planted in the water. Pay attention to feed nutrition, the combination of green, coarse and fine feeding.

4. Prevention of diseases and natural enemies

Sprinkle quicklime regularly, about every 20 days. River crabs are sensitive to pesticides and chemical fertilizers, using little or no pesticides (such as dimethoate, trichlorfon, etc.) as much as possible, and raising crabs in rice fields should also use less chemical fertilizer to avoid losses.

The damage caused by natural enemies of river crabs generally includes rodents, frogs, birds and so on. Effective protective measures should be taken to keep river crabs away from the threat of natural enemies.

Anti-escape and harvest fishing of crabs

Escape prevention is one of the keys to the success of raising crabs! Anti-escape facilities with glass steel tiles or calcium plastic board is better. Although the use of plastic film is economical, it is easy to aging, poor firmness and easy to damage. And the loophole is not easy to find, easy to cause escape crab. Often patrol the pond, one more careful, one more harvest. Insist on patrolling the pond once every morning and evening, often observe the feeding and activities of river crabs, regularly check the situation of escape prevention, especially before rain and wind, do a good job of inspection, find holes and repair them in time. Remove the residual bait and dead crabs in time.

Fishing should be carried out in a timely manner (pick up in the evening around mid-September).

There are a variety of fishing methods, which should be chosen according to the actual situation:

1. Trapping (making use of the phototaxis of river crabs).

2. Crab cage fishing.

3, release water fishing (river crabs like the current, suitable for buckle crabs to catch).

4. Net fishing or direct manual fishing.

To sum up, under such a stocking mode, if properly managed, the size of mature river crabs after autumn can reach 100-180 grams, and the recapture rate is also very high. According to the specification and grade standards, commercial crabs will be temporarily raised in small purse seine or temporary incubation boxes and put on the market at the right time. The economic benefits are considerable!