In traditional crab farming, crabs are usually stocked individually with uniform sizes. However, over the past few years, practical experience in large natural water bodies has shown that using a split seeding method can significantly improve economic returns. The following results were obtained from a field test conducted in a 158-mu natural river channel in the Shu area, which is connected to an external river system. The water flow is stable, with an average depth of 2.1 meters and a maximum depth of 3.5 meters. Two-thirds of the area is shallow, and the bottom consists of black loam.
Aquatic plants were introduced from August 2004 to May 2005, including 21 tons of algae and 203 kg of bitter grass seeds. Deep-water species like goldfish algae and shallow-water species like Vallisneria were planted, covering about 70-80% of the area. Snails were also introduced between November 2004 and April 2005, totaling 36 tons, including both original pond snails and 500 kg of additional snails. To manage water quality, lime was applied in November 2004 (14 tons) and quicklime in February 2005 (6 tons), resulting in clear water with a transparency of 1.5 meters and a pH of 7.5–8.5.
Crab seedlings were sourced from Sheyang Nursery in Jiangsu Province in late May 2004. These crabs were acclimated locally to reduce stress from long-distance transport and improve survival rates. In August 2004, 50,000 crabs with a size of 400–500 eggs/kg were stocked, followed by 31,000 fingerlings in July 2005 at 120–160 eggs/kg, for a total of 81,000 crabs. Additionally, 100 kg of young shrimp, 2,500 carp, and 1,500 carp fry were introduced in December 2004 and May 2005. Before stocking, all seedlings were disinfected in 3–5% saline for 10–15 minutes to remove surface bacteria and parasites.
Feeding began in mid-February, primarily using chilled fish with some formulated feed. From May to September, feeding was abundant, with about 8% of body weight provided daily, adjusted based on crab activity. Vallisneria served as an indicator of food availability—when there was enough food, fewer leaves were eaten, and when food was scarce, more leaves were damaged, signaling the need to increase feeding. Twenty to thirty days before harvest, high-protein animal feed was used to enhance crab health and market value. A total of 52,000 kg of feed was used throughout the year.
Preventing escape was a major focus, especially during rainy seasons when water levels rose quickly. Double barriers were installed at inlets and outlets, and nets were checked daily. During peak flood periods, staff worked around the clock to monitor and reinforce the barriers. Fishing started in late September, peaking in early October, using crab cages for efficient harvesting.
The economic results were impressive: 8,714 kg of market-sized crabs were harvested, with an average weight of 215 grams and a catch rate of 50.03%. Additional catches included 503 kg of carp, 8,493 kg of silver carp, 1,351 kg of green shrimp, and 2,487 kg of other fish. Total output reached 955,000 yuan, with crabs contributing 802,000 yuan. Total costs amounted to 3.8135 million yuan, resulting in a profit of 573.65 million yuan, or 3,631 yuan per mu.
Key lessons learned include the importance of stabilizing water flow by using stakes to secure barriers, especially in areas with multiple inlets and unstable water levels. Regular patrols are essential during rainy and flood seasons. Timely fishing of mature crabs helps prevent escape and improves overall yield. This approach proves that with proper management and adaptation, natural water bodies can be highly productive for crab farming.
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