The process of stocking fingerlings is a crucial step in aquaculture, directly influencing the success of fish farming and its economic and ecological outcomes. This article provides a detailed overview of key technical considerations, including timing, location, density, and disinfection methods, to ensure optimal results.
First, choosing the right season for stocking is essential. Early stocking helps maximize yield, as the saying goes: "Fish in spring will grow quickly, while those stocked in winter may only survive for three minutes." The best time for releasing fish is usually between the winter solstice and the beginning of spring. This allows fish to adapt to their new environment early, making it easier to manage them through the winter and promoting better growth in the spring. In the Yangtze River region, stocking typically occurs before the Spring Festival. In the northeast and northern China, it's ideal to stock once the water temperature stabilizes around 5–6°C after thawing. Lower temperatures are preferable because they reduce fish activity, making handling safer and less stressful, which increases survival rates. Additionally, lower water temperatures mean fewer pathogens, reducing disease risk. Winter stocking also minimizes predation by larger fish, which tend to be less active during this time.
Second, the timing of stocking should be on a sunny day, preferably at noon. Avoid stocking during cold, rainy, or snowy weather to prevent frostbite. For large water bodies like lakes and reservoirs, it’s best to choose a period of 5–7 days with favorable conditions, allowing temporary holding areas to help fish gradually adjust to their new environment, thus improving survival and growth.
Third, the location of stocking matters. Avoid placing fingerlings near inlets, outlets, spillways, or pumping stations, as strong currents can harm them. Also, avoid shallow areas near the outlet where waves might damage them. Don’t concentrate fish in one spot to prevent predators from gathering. In low-water winter conditions, avoid placing fish in upper reaches or shallow parts of rivers to prevent stranding. Instead, choose sheltered, well-fed, and appropriately deep locations.
Fourth, stocking density must be carefully managed. A reasonable density ensures maximum yield without overstocking, which can lead to poor water quality, low oxygen levels, and increased stress on fish. Factors such as pond size, water quality, fish species, feed availability, and management practices all influence the ideal density. While higher densities can boost production, they must be balanced with adequate feeding and proper water management to avoid negative consequences.
Finally, disinfecting fingerlings is a vital step before stocking. Even healthy fish may carry pathogens that could cause disease if not treated. Common disinfectants include bleaching powder, potassium permanganate, salt, trichlorfon, and Weikang, which is EPA-approved and effective against a wide range of pathogens. Soaking fish in a 10–30 ppm Weikang solution for 10–30 minutes is highly effective. When using any disinfectant, follow instructions closely, use non-metal containers, avoid direct sunlight when using potassium permanganate, and handle fish gently to prevent injury. Always monitor fish during treatment and remove them immediately if signs of distress appear. For large numbers, consider using a plastic film box for dipping. After disinfection, do not pour the solution into the pond. (Hu Huaming, Motion Protection Institute)
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