Freshwater shrimp non-harmful aquaculture: Key points, difficulties, and case studies

Author: Xu Zaiquan / Country: Mainland China
Publisher:
Publish Date: 2005-05-01
Features: [Excerpt:] 8. Winter Culture of Crayfish in Paddy Fields
Winter culture of crayfish in paddy fields is a model that utilizes idle ditches after the winter harvest of crayfish or shrimp ponds after the harvest of Macrobrachium rosenbergii. The following technical points should be mainly mastered:
(1) Clean the shrimp ditches and stock them at the right time in late October or November. After harvesting crayfish or Macrobrachium rosenbergii, immediately select some shrimp ditches in paddy fields with relatively deep water and good conditions, remove excessive silt from the ditches, repair and reinforce the bunds, and inject fresh river water. If the paddy field still needs to grow a season of rapeseed or wheat, the water level in the shrimp ditches should be kept at 1.2 meters. If rapeseed or wheat is not grown, the entire paddy field can be used for crayfish culture. Once the shrimp ditches are cleaned, stocking can begin. The sources of shrimp seedlings mainly include three channels: First, select small shrimp with a size of less than 4 cm left over from the previous harvest of crayfish as seedlings. Second, culture shrimp seedlings in ponds with good conditions. By stocking sufficient shrimp seedlings and raising them carefully, the seedlings can reach a size of about 3 cm around late October, ready for winter stocking. Third, purchase small, healthy crayfish of appropriate size from the market, or collect them from fish seedling farms or adult fish farms. Usually, 20,000 to 25,000 seedlings with a size of 2 to 4 cm can be stocked per mu of shrimp ditch water. The best stocking time is mid-December. Early stocking allows the seedlings to adapt to the paddy field environment earlier, start feeding earlier, and promote growth.
(2) Provide sufficient feed and manage meticulously. In winter culture of crayfish in paddy fields, the feeding strategy is to "focus on the beginning and end, and moderate the middle." After stocking in December, take 15 to 20 days to focus on high-quality feed, with a daily feeding rate of 5% of the weight of crayfish in the field. From January to February, due to the cold weather, crayfish only forage on sunny and warm days. Therefore, only a small amount of feed can be given on sunny days. Starting from March, as the weather warms up and water temperature rises, crayfish gradually increase their feeding intensity. Seize this favorable opportunity to manage feed well. In March, the daily feeding rate can be set at 3% to 5%, increasing to 6% in April. May is the spawning and carrying stage of crayfish, and also the fastest growth season. The daily feeding rate can be increased to 8%, with 3 to 4 feedings per day, striving to ensure that the crayfish reach a size of over 5 cm by mid-to-late May. Strengthen management during winter culture of crayfish. From January to February, during cold weather, inspections. If the water surface freezes, break the ice promptly to increase oxygen and prevent crayfish from suffocating due to ice. From March to May, strengthen water quality management. Determine the frequency and volume of water exchange in the shrimp ditches based on water color. When adding water, choose sunny and warm days, around 11 a.m., when the temperature of the external river water is close to that of the shrimp ditch water to avoid large temperature differences. Maintain stable water temperature and water level in the shrimp ditches.