Preparation Before Stocking
Pond Disinfection
Before stocking, it's essential to thoroughly disinfect the aquaculture pond. A 15-25 cm deep pond should be treated with 75-80 kg of quicklime per mu, evenly spread across the bottom. This helps eliminate harmful organisms and pathogens. After applying the lime, let it dry for 3-4 days before adding water to a depth of 5-10 cm. Then, apply a long-lasting water disinfectant to ensure all pathogens and pests are effectively eliminated.
Cultivating Basic Food Organisms
The cultivation of basic food organisms typically begins 10-15 days before releasing the seedlings. Once the pond is clear, fill it with water to a depth of about 50 cm. Use fermented organic fertilizer or microbial preparations to enrich the water. Apply approximately 100-150 kg of organic fertilizer or 1-1.5 kg of biofertilizer per mu to encourage the growth of natural feed. The water should turn yellow-green or tea-brown, with a transparency of 25-35 cm and a pH around 8. This environment provides optimal conditions for the shrimp to grow.
Shrimp Selection and Temporary Rearing
Choosing Healthy Shrimp
When selecting Penaeus vannamei seedlings, choose those that are healthy, active, and have uniform size. They should have a slender body, clean surface, well-developed muscles, full stomachs, and show strong reactions to external stimuli. Their bodies should be transparent without any visible lesions. It's best to stock shrimp that are at least 2 cm in size, though 1.2-1.5 cm is commonly used. Smaller sizes can lead to lower survival rates.
Temporary Rearing Standards
Early-stage shrimp should be reared in a nylon greenhouse (or a similar structure) for 10-20 days. The timing of this process depends on weather conditions. When moving them to outdoor ponds, the water temperature should be at least 20°C; otherwise, their growth may be affected. The ideal time to start temporary rearing is usually around mid-April. If needed, a boiler can be used to warm the water earlier. The stocking density during this period should not exceed 1500-2000 individuals per cubic meter. Ensure good water quality and sufficient dissolved oxygen. During desalination, adjust the salinity gradually—no more than 1 unit per day—until it reaches 1-1.5‰, matching the salinity of the nursery pond. At this point, the shrimp can be released. In later stages, small holding pools can be created using plastic sheets in empty corners of the pond to reduce the time needed for desalination, usually 7-10 days.
Feeding during temporary rearing is important. Initially, feed them with crushed insects or filtered liquid after washing the shrimp. Start feeding after 4 days, beginning with 5-10 grams per 10,000 shrimp, feeding 5-6 times daily. Increase the amount by 20-30% each day. Once the shrimp reach 1.5-2 cm in length, they can be moved to the main rearing pond.
Stocking the Shrimp
Timing is crucial when stocking Penaeus vannamei. The optimal water temperature is between 20-30°C, as this range promotes fast growth and strong immunity. Stocking should be done in the morning or late afternoon on sunny days. Avoid exposing the seedlings to direct sunlight at noon or during cloudy rainy weather. In our region, the best time to plant seedlings is in mid to late May.
Appropriate stocking density depends on pond conditions. If the water quality is good, drainage and aeration systems are efficient, and the pond is well-maintained, a density of 35-40,000 per mu is recommended, and even up to 50,000-60,000 per mu can be achieved. This density ensures high yields and consistent shrimp sizes at harvest.
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