Technical Measures before Shrimp Restocking
1. Dredging and Disinfection
After harvesting shrimp or during seasonal changes, it's essential to clean the pond thoroughly. Start by brushing the walls and draining all the water. Remove sludge and debris completely from the pond. For black mud, take as much as possible and transport it away from the pond area to avoid future issues. Once dredged, rinse the pond until no dark sewage remains. After draining, allow the pond to dry slightly before introducing a suitable amount of clean seawater or freshwater. Use strong disinfectants like Texiaoling, dibromohydantoin, or bromochloroacetic acid for effective pond disinfection. Ensure the disinfectant is evenly distributed throughout the water. In areas that are not fully soaked (including the pond walls), use a tool to apply the solution and let it soak for several days. During this time, if any floating dirt appears, remove it before 5 p.m. After a few days, drain the disinfectant and inspect the pond. If there is still biological residue, 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 desired water level (which may vary depending on the season), first check for the presence of rotifers, dinoflagellates, noctiluca, or other microorganisms. Also, test salinity and pH levels. If harmful organisms are found, use appropriate chemicals to eliminate them. If seawater is free from these organisms, opt for disinfectants that kill harmful bacteria without harming beneficial algae, such as dibromohydantoin or bromochlorohydantoin. After disinfection, retest pH and salinity. If the pH is below 8.0, add lime powder to raise it. If the water is muddy, consider applying 50–80 kg of dolomite or zeolite per mu to improve the bottom substrate.
3. Fertilizing the Water
Fertilizing the water is a crucial step in shrimp farming. It directly affects the early survival rate of the shrimp. Proper plankton levels ensure better growth and higher yields. For optimal results, maintain a water transparency of 30–40 cm. Green prawns (Penaeus lobata) prefer brown water dominated by Chaetoceros species, while white shrimp (Penaeus vannamei) thrive in yellow-green or green water. Here are some recommended fertilization methods for a water depth of 1 meter:
(1) Living 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 sprayed.
(3) Tea Bran: 3–4 kg per mu for earthen ponds, 6–7 kg for sandy ponds, and 8–10 kg for sloped ponds. Soak for 4–7 days, then filter and pour into the water.
(4) Sodium Dihydrogen Phosphate or Potassium Dihydrogen Phosphate: 10 g per cubic meter of water, evenly scattered after watering.
(5) Compound Fertilizer: 2–3 kg per acre, applied every 1–2 days, 1 kg each time, and evenly spread after watering.
4. Seed Selection
Selecting high-quality seedlings is critical to successful shrimp farming. Choose healthy, virus-free, and disease-free specimens. Here are some visual guidelines for selection:
For Penaeus lobata (green prawns): Seedlings should be over 1.1 cm in size, uniform in size, clean, with normal coloration, no attachments, active swimming, able to swim against the current, and have straight bodies. Their eyes should remain open when not swimming, and their tail fins should flutter briefly.
For Penaeus vannamei (white shrimp): Seedlings should be 0.9–1.0 cm long, with transparent bodies, uniform size, plump stomachs, strong appetite, active movement, and good resistance to water currents. They should have clean surfaces, consistent color, and a large head with a small body.
5. Seed Transportation and Pre-Disinfection
During transportation, especially over long distances, seedlings can suffer stress and lose vitality. To improve survival rates, pre-pack the seedlings in 0.3 m³ of water with 100 g of immunopolysaccharide or 30–50 g of G-D. Stir well and use this water to hold the seedlings during transport. Upon arrival, disinfect the seedlings using a suitable disinfectant, such as Qianke 101 (a quaternary ammonium iodine compound). Mix 0.5–1 g per half-mu of water and soak for 30 minutes before releasing them into the pond.
6. Setting Up Feeding Stations and Aeration Systems
Each shrimp pond should ideally have feeding stations on both the east and west sides. These help monitor feeding behavior, feed consumption, and shrimp health. Observing the feeding station allows you to assess stomach fullness, waste production, and distribution patterns, which helps determine whether to adjust feed amounts accordingly.
Aerators are typically matched at 1 horsepower per acre. If stocking density exceeds 60,000 per acre, more aerators may be needed. It's best to use a combination of impeller, submersible, and nano-tube aerators for better efficiency. Proper aeration prevents oxygen depletion, improves water quality, and enhances overall pond conditions.
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