Using wild crabs to idle ponds

Macrobrachium rosenbergii, a tropical shrimp species, is commonly farmed in the middle and lower reaches of the Yangtze River and southern regions. The adult shrimp are typically sold between September and mid-October, when prices are relatively low. However, from November to New Year's Day, live shrimp in the market face a shortage, leading to price increases. During this time, V-breasted crab ponds are usually idle, except for the period from January to May. To make use of this downtime, farmers began holding Macrobrachium rosenbergii, which proved highly profitable. Two ponds, measuring 820 square meters and 720 square meters respectively, yielded 450 kilograms of Macrobrachium rosenbergii and also held 950 kilograms of commercial shrimp for a short period. This operation generated a net income of over 20,000 yuan. The following is a detailed description of the technology used: I. Time Coordination and Pond Preparation The young crabs were caught from the net ponds before the end of May. The ponds were sterilized in early June, and shrimp were stocked on June 10, raised until late October. Some ponds were also used for raising commercial shrimp. In November, Daliu Xiaoxiao was launched for sale, and by the end of the New Year’s Day season, Tengtang used the young crabs for the next cycle. Preparations included pond renovation, installation of intake and drainage pipes, aerators, wintering plastic greenhouses, boilers, and heating systems. Before stocking, the ponds were cleaned, filled with fresh water, fertilized with decomposed animal manure, and planted with aqua peanuts every 20 square meters. II. Shrimp Stocking and Feeding Management Shrimp were raised on sunny days, ensuring that the temperature difference between ponds was not too significant. Post-larvae were stocked at 25,000 to 30,000 per acre, and after being raised in the middle stage, about 2,000 to 5,000 larvae per acre were stocked. Initially, feed with 35% to 40% protein was used, and later, a mix of snails, quail meat, bean cakes, and bran in a 1:1 ratio was fed, along with added calcium and phosphorus. Feeding followed the “four principles” of qualitative, quantitative, fixed-point, and regular timing. The initial feeding rate was 15% of total shrimp weight, gradually decreasing to 4%. Adjustments were made based on water temperature, weather, shrimp behavior, and feed type. Daily observations were conducted in the morning, evening, and midnight to check water clarity, shrimp distribution, feeding activity, and growth. Water was regularly added and changed, and medications were used to prevent disease. Oxygen levels were maintained, and water peanut attachments were managed properly. III. Winter Holding of Commercial Shrimp When the water temperature dropped to 20°C, plastic film greenhouses were covered. Ponds were drained, cleaned, disinfected, and then refilled. Healthy, full-sized commercial shrimp (40–60 per kilogram) were stocked at 400–500 kg per mu. After stocking, proper heating, oxygenation, water changes, and feeding were ensured. The greenhouse water temperature was kept between 18°C and 20°C. If it dropped, the boiler was used to warm it up. Dissolved oxygen levels needed to be above 3 mg/L; if rainy days occurred, the aerator was activated. If the temperature was too high, new water was replaced to maintain quality. During the holding period, 3% to 5% of the shrimp's weight was fed daily to ensure their health and survival. IV. Shrimp Harvesting and Transportation The timing of harvesting depended on water temperature and market demand. The main purpose of holding was to supply live shrimp during winter, especially around New Year’s Day. On weekdays, nets were used for fishing as needed, while large-scale draining was done before festivals. Shrimp caught in dry ponds should be washed in cages promptly to avoid quality loss or death. Live shrimp can be transported using water tanks, fish bowls, or air-conditioned vehicles, with continuous aeration.

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