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River Crab Mesh Ecoculture Technology
Eriocheir sinensis, commonly known as the Chinese mitten crab, has a rounded, cuboidal head with a broader posterior than anterior section. Its forehead features four teeth, with a distinct notch between them, deepest in the center. The front margin has four sharp teeth, with the last one being the smallest. Males have larger chelipeds compared to females, and both the inner and outer sides of the knuckles are covered with fine hairs. The inner corner of the wrist joint has one sharp tooth, while the dorsal margin near the base and the step foot section also have one sharp tooth. The last three pairs of legs are relatively flat, with bristles on the wrist and back parts. The first pair of legs and the base of the knuckles are densely covered with bristles. Female crabs have a round abdomen.
Net-based aquaculture is an ecological method that utilizes natural food sources such as aquatic plants, snails, and small fish, combined with simple feeds like corn and grains to mimic a natural food chain. This approach creates a wild-like environment that enhances crab quality, reduces disease incidence, lowers production costs, and increases economic returns. The water area should be a reservoir or lake with open water, gentle currents, and meet GB11607-1989 water quality standards. The net site should avoid busy waterways, be quiet, and have convenient access. The surrounding area should have abundant aquatic vegetation, high density of benthic organisms, and minimal predators. The bottom should be flat, suitable for clay or sand, with a consistent water depth of 1–2 meters and transparency above 1 meter, along with dissolved oxygen levels of at least 5 mg/L.
Net enclosures are constructed using polyethylene mesh (33 mesh), with anti-escape measures including a gabion at the base made from 2 cm polyethylene net. Bamboo poles (8–10 cm diameter, 5 m long) are used for support, and polyethylene rope and wire are used for binding. The net enclosure area should generally be 2–4 hectares, with shapes like circular, oval, or rectangular depending on the environment. A double-layer escape prevention system is recommended: an internal 2 cm mesh and external 3 cm mesh, spaced 3–4 meters apart. The fence height should extend 1.5 m above water level, with a 1 m wide raft net at the top, angled at 50–70 degrees. A 25 cm high calcium plastic plate is added for extra safety.
Crab stocking involves selecting healthy individuals, typically from Yangtze River strains, with uniform size, no deformities, and clear coloration. Before stocking, predators must be removed. Crabs are disinfected by soaking in saltwater or potassium permanganate solution. Stocking usually occurs from December to February, with densities ranging from 9,000 to 12,000 per hectare. Aquatic plants are essential, and crabs should be distributed evenly to prevent overcrowding.
Feeding includes aquatic plants, corn, wheat, pumpkin, and animal-based feeds like snails and fish. Feeding schedules follow a "two thick, one medium" pattern, adjusting based on water temperature and growth stages. Daily feeding is done once in the afternoon, with plant feed making up 2–5% of total weight and animal feed 2–3%. Feeding methods include soaking and cooking plant materials, chopping animal feed, and ensuring even distribution to reduce aggression.
Regular sampling helps monitor growth and adjust feeding accordingly. Daily management involves checking for escaped crabs, maintaining water quality, and controlling predators. Disease prevention relies on clean water, fresh feed, and regular monitoring without chemical use.
Harvesting occurs between November and December, using traps or cages. Crabs are temporarily held in cages (1.5m x 1.5m x 0.8m) with a maximum stocking capacity of 50 kg per cage. This method ensures quality and market readiness.