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Cultivation Techniques of Yellow Catfish Fry
Stingray fry have specific biological needs that must be carefully managed to ensure their healthy development. First, their living environment plays a crucial role in their survival. Stingray fry are sensitive to environmental changes and require stable conditions. The ideal pH level for their growth is 7.0, and deviations below 6.5 or above 8.0 can lead to health issues such as skin discoloration, increased mucus production, and even disease outbreaks. The optimal water temperature range is between 22°C and 27°C, with a minimum of 15°C and a maximum of 32°C. Water quality is also important, with dissolved oxygen levels needing to stay above 5.0 mg/L.
In terms of feeding, stingray fry start with endogenous nutrition, relying on the yolk sac for the first few days. By day 3, they begin to transition to exogenous feeding, and by day 5, the yolk sac is completely absorbed. At this point, the fry are around 8 mm long and fully dependent on external food sources such as rotifers and small zooplankton.
Growth is rapid during the early stages; within 30 days, fry can increase their weight by more than ten times. However, as they mature, their growth rate gradually slows down. This makes early care and feeding especially critical for their development.
For successful cultivation, the pond setup must meet certain standards. The pond should have a reliable water source, good drainage, and a clean, toxin-free environment. It should be rectangular, ideally oriented east-west, with a length-to-width ratio of 5:3. The area should be between 1 mu and 2 mu, with a depth of 0.8 to 1.2 meters. The bottom should be flat and free of debris, and new cement ponds need to be thoroughly washed before use. The water pH should be maintained between 7.0 and 7.8.
Before stocking, the pond needs thorough preparation. Earthen ponds should be cleaned, silt removed, and the bottom leveled. Concrete ponds should be scrubbed and left to dry. Lime is often used to disinfect earthen ponds and eliminate unwanted organisms. Water sources must be clean and filtered through a 40-mesh sieve to prevent contamination from other fish, insects, or debris. If using tap or well water, chlorine must be removed before introduction.
Transporting the fry requires careful handling. Before transport, fry should be acclimated for 3–5 hours in a holding cage. They are then placed in oxygenated plastic bags (70 cm x 40 cm, 8–9 L capacity) and packed in foam boxes. Each bag can hold up to 150,000 fry, and transport should last no longer than 10–15 hours. Leak checks are essential during transit.
Once in the pond, the fry should be introduced gradually. The water temperature in the transport bag should match that of the pond before release. Feeding begins with cooked egg yolk passed through an 80-mesh sieve once the fry show active swimming behavior.
Daily management includes feeding soybean milk (15–17 kg per mu) at morning, afternoon, and evening. Regular monitoring of rotifer populations using a microscope helps determine when to apply organic fertilizer (50–100 kg per mu). Water levels should be kept at 50–60 cm, with partial water changes every six days. Net exercises are conducted to improve fry resilience, and algae should be regularly removed. Daily records of fish activity, feeding, and water parameters help maintain optimal conditions and guide future practices.