Technical Measures before Shrimp Restocking
1. Dredging and Disinfection
After harvesting shrimp, it's essential to clean the pond thoroughly. Begin by scrubbing the walls and draining all the water. Remove sludge and debris completely from the pond. For black mud, try to remove as much as possible and transport it away from the pond area to prevent future problems. Once dredged, rinse the pond until no dark wastewater remains. After draining, expose the pond to sunlight for a few days. Before introducing new seedlings, add a suitable amount of clean seawater or fresh water and apply strong disinfectants such as Texiaoling, dibromohydantoin, or bromochloroacetic acid. Ensure the solution is evenly distributed in the water. For areas that are not fully soaked, use a tool to spray the liquid and let it sit for several days. If any floating debris appears during this time, remove it before 5 p.m. After a few days, drain the solution and inspect the pond. If any biological residue remains, remove it and refill with water. When adding new water, install a 80-100 mesh filter at the inlet to prevent unwanted organisms from entering.
2. Water Disinfection and Quality Testing
Once the pond is filled to the appropriate water level (adjusted based on the season), check for the presence of rotifers, dinoflagellates, noctiluca, and other microorganisms. Also test salinity and pH levels. If harmful organisms are detected, use appropriate treatments to eliminate them. If seawater is free of these organisms, use disinfectants like dibromohydantoin or bromochlorohydantoin that effectively kill bacteria without harming algae. After disinfection, retest the pH and salinity. If the pH is below 8.0, add lime powder to raise it. In case of muddy sediment, apply dolomite or zeolite powder (50–80 kg per mu) to cover the sludge and improve water quality.
3. Fertilizing the Water
Fertilizing the water is a crucial step in shrimp farming, directly affecting the survival rate of the young shrimp. The initial water clarity should be around 30–40 cm. For Penaeus lobata (green prawns), brown water dominated by Chaetoceros species is ideal, providing zooplankton for larvae. For Penaeus vannamei (white shrimp), yellow-green or green water is preferred, especially in freshwater conditions. Here are some fertilization methods for reference (for a water depth of 1 meter):
(1) Live Water (Microbial Fertilizer): 1 kg per mu, sprayed into the water.
(2) Hyaluronic Acid (Bacillus subtilis): 350–400 g per mu, mixed with water and applied.
(3) Tea bran: 3–4 kg per mu for earth ponds, 6–7 kg for sandy ponds, and 8–10 kg for sloped ponds. Soak for 4–7 days, filter out the residue, and then pour the mixture into the water.
Sodium Dihydrogen Phosphate or Potassium Dihydrogen Phosphate: 10 g per cubic meter of water, evenly distributed after watering. Compound fertilizer: 2–3 kg per acre, with 1 kg added every 1–2 days, evenly spread after watering.
4. Seed Selection
Selecting high-quality shrimp seedlings is vital for successful farming. Choose healthy, virus-free, and bacteria-free specimens. Here are some visual criteria:
Penaeus lobata (green prawns): Must be over 1.1 cm in size, uniform in size, clean body surface, normal color, no attachments, active swimming, can swim against water flow, straight body shape, and both eyes open when not swimming.
Penaeus vannamei (white shrimp): Size between 0.9–1.0 cm, transparent body, uniform size, full stomach, active movement, strong resistance to water, clean surface, even color, good health, and a large head with a small body.
5. Seed Transportation and Pre-Disinfection
During transportation, especially over long distances, some shrimp may die or lose vitality. To ensure survival and maintain vigor, add 100 g of immunopolysaccharide or 30–50 g of G-D to 0.3 m³ of water in the transport container. Mix well and use this water to hold the seedlings. Upon arrival, disinfect the seedlings using a solution like Qianke 101 (a super iodine quaternary ammonium salt), at a concentration of 0.5–1 g per half-mu, soaking for 30 minutes before releasing them into the pond.
6. Setting up Feed Stations and Aeration Systems
Each shrimp pond should have a feed station on both the east and west sides to monitor feeding behavior and feed quantity. Observing the feed station helps assess the shrimp’s satiety, feed consumption, feces, and distribution, allowing for adjustments in feed amounts. Aerator systems are typically matched at 1 horsepower per acre. If the seedling density exceeds 60,000 per acre, more aerators may be needed. It is best to use three types of aerators—impellers, submersible units, and nano-tubes—for optimal performance. Aeration prevents oxygen depletion, improves water quality, and enhances overall pond conditions.
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