At present, the artificial breeding of yellow catfish has captured the interest and support of many farmers. Through years of practical experience, it has been confirmed that large-scale fry production in under-fish ponds significantly improves the survival rate of stingray aquaculture. The yield can reach approximately 400 kilograms per 667 square meters (1 acre), which leads to better economic returns. Below are the summarized techniques for raising stingray fry.
**Pond Conditions**
The pond should be between 0.2 to 0.33 hectares in size, with a water depth of 1 to 1.2 meters. It is important that the water source is abundant, the water quality is good, and the drainage and irrigation systems are efficient. The pond structure must be solid, without leaks, and the bottom should be flat with minimal silt accumulation.
**Pond Disinfection**
Before stocking, leave about 10 to 20 centimeters of water in the pond. Apply 80 grams of lime per 667 square meters. Once the lime dissolves, pour the hot lime water evenly into the pond. The next day, use a shovel to turn the mud and mix it thoroughly with the lime slurry. This process helps eliminate wild fish and harmful organisms, while also encouraging dormant plankton eggs in the mud to hatch.
**Water Filling and Fertilization**
After disinfection, start filling the pond on the third day, with a water depth of around 70 centimeters. Use a 40-mesh net at the inlet to prevent predators from entering. Then, add 150 kg of fermented manure or 50 kg of soybean milk per 667 square meters. This enriches the pond with plankton, making the water rich in natural food sources.
**Fry Handling and Transportation**
Fry can be transported using oxygenated bags. Before transportation, keep the fry in a cage for 5 to 6 hours to help them adapt and expel waste, reducing pollution during transit. Well water is ideal for transport, but if not available, use low-organic water. In high temperatures, ice can be added to maintain a stable temperature.
**Stocking Fry**
To ensure the fry have enough food like rotifers and small cladocerans, it is best to start stocking 8 to 10 days after pond preparation, when these microorganisms are at their peak. When releasing the fry, make sure the temperature difference between the transport water and pond water does not exceed 5°C. Stocking is best done on a sunny morning, with a density of 40,000 to 50,000 fry per 667 square meters, each about 0.8 to 1 cm long.
**Daily Management**
Throughout the fry rearing process, natural food sources are essential. Ensuring sufficient and nutritious food at all developmental stages is crucial for successful fry cultivation. Check the food biomass in the pond every morning and evening. After 3 to 5 days of feeding, the food supply may decrease, so add organic fertilizer every two days—about 10 to 15 kg per 667 square meters. Alternatively, supplement with plankton from other ponds. Every other week, add 10 to 20 cm of fresh water to maintain good water quality. After 12 to 15 days, the fry will grow to about 3 cm, with a survival rate of 80% to 90%.
**Disease Prevention and Treatment**
Stingrays generally have strong disease resistance, especially when water quality is well maintained. Routine disinfection is rarely needed. However, if treatment is necessary, only approved, safe, and effective medicines should be used. Since stingrays lack scales, they are sensitive to certain chemicals like trichlorfon and copper sulfate. It is best to avoid these drugs altogether.
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