Cages used in aquaculture come in two main types: small cages of 4m² and large cages of 25m², each designed for different farming systems. The small cage measures 2m x 2m x 1.7m with a submersion depth of 1.5m, while the larger one is 5m x 5m x 3.5m, submerged to 3m below the water surface. These cages are constructed from braided polyethylene mesh, with outer netting of 3.5–4.5 cm and inner netting of 2.5–3.5 cm. A single-layer cover net extends upward from the inner mesh to protect the fish. The cages are mounted on square bamboo frames, which are 60–120 cm wider than the cage itself to ensure full mesh expansion. The bottom corners are suspended to keep the base level, allowing smooth water exchange and free movement of the fish.
The feeding system varies depending on whether the feed is sinking or floating. For small cages using sinking feed, a food table made of 40-mesh polyethylene cloth is placed at the bottom of the cage, connected to the walls. A plastic tube delivers feed from a hopper to the table. A mesh layer covers the lower part of the cage to prevent feed loss and tilapia from entering the pipe. Floating feed cages use a buoyant table made of steel and mesh, fixed in the center of the cage. It is 50 cm tall, with the top attached to the cover net and the bottom submerged 30 cm underwater to keep the feed in place.
When selecting a breeding environment, it's important to choose unpolluted freshwater reservoirs with good transparency (over 1 meter) and dissolved oxygen levels above 5 mg/L. Cages should be placed in areas with minimal wave action, good water circulation, and low current speeds (under 0.2 m/s). They should also be near accessible transport routes and away from major reservoir channels. Large cages are arranged in groups of three, tied together with thick ropes and anchored to trees or cement piles. Small cages are placed in single rows, spaced more than 4 meters apart, while large cages are grouped with over 30 meters between them and 80 meters between rows.
Fish stocking typically occurs between late April and May when water temperatures stabilize above 20°C. Before stocking, cages must be checked for damage and secured. Fish should be healthy, of uniform size, and disinfected in a 3–5% salt solution for 5–10 minutes before being carefully placed into the cages. In small cages, 500–1000 fingerlings weighing over 20g are stocked, while large cages can hold 3000–4000 fish, depending on size and conditions.
Feeding practices change as fish grow. Young fish (around 50g) are fed 2–3mm pellets with 30–32% crude protein, while those over 100g receive 3–7mm feed with 28–30% protein. Moldy or contaminated feed should be avoided. Feeding frequency depends on water temperature: 2–3 times daily when temperatures range from 18–23°C, increasing to 3–5 times when temperatures reach 23–31°C, and reducing to 1–2 times when temperatures drop to 25–15°C.
Daily management includes checking nets for damage, cleaning the cages monthly, adjusting positions with water level changes, and monitoring fish behavior and water quality. Disease prevention involves regular disinfection using bleaching powder and maintaining clean equipment. If disease occurs, prompt treatment is essential.
Harvesting usually takes place between May and July when tilapia reach commercial sizes of 0.5–1.6 kg. A small 4m² cage can yield up to 500kg, while a 25m² cage produces around 2000kg. With proper management, one worker can handle 150 small cages, producing 75 tons, or 12 large cages yielding 24 tons. Profitability is significant, with per capita production values reaching up to 600,000 yuan and profits of 150,000 yuan.
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