The use of non-feeding cages for raising calyx is an efficient method that maximizes the utilization of aquatic biological resources and reduces aquaculture costs. This technique has proven to be both effective and sustainable. Here’s a detailed overview of the process:
First, cage structure. The most commonly used cages are rectangular floating enclosures made from polyethylene mesh. Typical dimensions include 4m x 6m x 2m, 4m x 7m x 2m, or 4m x 8m x 2m. These cages are usually single-layered, and the mesh size is carefully selected to prevent fish from escaping while allowing sufficient water flow. A general rule is to ensure that the mesh is small enough to hold fish but large enough to avoid damaging them.
Second, cage placement. It's important to install these cages in sheltered areas with good water quality, abundant plankton, and minimal pollution. Ideal locations include upper reservoirs or similar bodies of water. The depth should ideally range between 5 to 8 meters. If the water is too deep, it may lead to a lack of food organisms, which can hinder fish growth. Additionally, there should be a gentle current, no more than 0.1 m/s, to ensure proper water circulation. In areas with rich nutrients, the total cage area should not exceed 1% of the total water surface. In less productive waters, this limit should be reduced to 0.5%. When multiple cages are used, they should be arranged in series with at least 10 meters between each and 50 meters between groups. This helps increase water exchange and supports better fish growth. Cages can be fixed using ropes tied to both sides of the water body.
Third, fish species. Before stocking, the cages should be placed 7 to 10 days in advance to allow algae to grow on the net, making it smoother and reducing the risk of injuring the fish. Fish are typically introduced during autumn or early spring when water temperatures are favorable, and their scales are tightly packed, leading to higher survival rates. Before entering the cage, fish must undergo thorough disinfection, depending on their health, water temperature, and the concentration of the disinfectant. Any signs of distress should prompt immediate action. To maximize economic returns, larger fingerlings (18–23 cm) are recommended to shorten the growing period. Stocking density varies based on water conditions, but a typical range is 15–20 fish per square meter.
Fourth, daily management. Regular inspections are essential, with checks conducted at least once a week. More frequent checks are needed after heavy rain or flooding. Special attention should be given to the area 30 cm below the water surface, as this is where water rats may damage the net.
Cage cleaning is also crucial, as filamentous algae and other organisms can accumulate and clog the mesh, reducing water flow. The more nutrients present, the more organisms will attach, and smaller mesh sizes tend to trap more debris. Therefore, it's important to replace cages with larger mesh sizes as the fish grow, ensuring better water exchange and faster growth.
Mobile cages should be moved according to changes in water level, quality, and food availability. This helps avoid unfavorable conditions and ensures optimal fish development. Disease prevention is generally straightforward, but anchor lice can be a concern. Using methods like hanging or spraying can help keep the fish healthy and disease-free.
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