Wintering Technology of Tilapia Fish Species in Greenhouse

Winter fish breeding technology involves several key stages and management practices aimed at ensuring optimal growth and survival of fingerlings, particularly in controlled environments like greenhouses. The greenhouse is a rectangular structure measuring 34 meters in length and 23 meters in width, covering an area of approximately one acre. It features stone walls and an earthen bottom with a depth of 3 meters. The pond is equipped with an intake and drainage system, along with a 1.5 kW impeller aerator to maintain good water quality. The fingerlings used for this project are Anoxis species, categorized into large (average weight 42 g/fish, 80% of the population) and small (average weight 25 g/fish, 20% of the population). The male ratio is as high as 93%, which helps improve growth performance. Before stocking, the greenhouse undergoes thorough preparation. Weeds are cleared in mid-September, and the roof and walls are inspected and repaired. Plastic film is applied in late September to ensure insulation. The pond is cleaned in early September, with sludge removed using a mud pump and disinfected with calcium oxide (100–150 g/m³). After 7 days of disinfection, the pond is refilled with water to a depth of 1.5 meters. A 40-mesh sieve is installed at the inlet to prevent unwanted organisms from entering. Chlorine bleach (1 g/m³) is used for final disinfection, followed by aeration to mix the water. Fingerlings are stocked between September 20th and 30th. They are fasted for 3 days before being moved, and only uniformly sized fish are selected for stocking. Before introduction, they are disinfected with copper sulfate (8 mg/L) and bleach (10 mg/L) for 5–10 minutes. Water temperature differences between the greenhouse and the fish pond are kept below 3°C, with a stocking density of 45–50 fish per square meter. During the pre-culture phase (late September to mid-November), the focus is on feeding, water quality control, and disease prevention. Fish are fed twice daily with self-developed compound feed containing 31–32% crude protein and 5–6% crude fat. Large fish receive 2.0 mm pellets at 2.0–2.5% of body weight, while small fish get 1.5 mm pellets at 2.5–3.0%. Water is changed every 2–3 days, and aeration is used to maintain dissolved oxygen levels. By mid-October, the water level is raised to 1.8 meters, and physical and chemical parameters are maintained at 22–23°C, 3–4 mg/L dissolved oxygen, and 30–35 cm transparency. Disease management includes treating fungal infections with Quanchiposa and florfenicol, and managing trichodermosis with copper sulfate and ferrous sulfate. During the mid-winter period (November to March), feeding frequency is reduced, and higher-energy feed (28% protein, 7–8% fat) is used. Water is changed more frequently, and the water level is raised to 2.0 meters. In the late stage (March to May), water changes occur daily, and photosynthetic bacteria are added to improve water quality. Aerator use is adjusted to maintain dissolved oxygen levels, and plastic film is gradually removed as temperatures rise. Common diseases during this phase include trichodiasis, enteritis, bacterial gill disease, and fatty liver disease, each requiring specific treatments. To improve efficiency, the author suggests three main measures: implementing water recycling with ozone and biological purification to reduce hot water usage, increasing the male ratio to over 95%, and improving fry size through relay culture in greenhouses and outdoor ponds. These strategies aim to enhance productivity, reduce costs, and improve overall fish health.

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