1. The incubation loop (barrel) nursery is a specially designed water system that mimics natural ecological conditions and keeps the eggs in constant motion. Using this method directly raises fish fry, providing them with an ideal living environment. More importantly, when the fry hatch and start feeding, they consume small bait fish—other live fry that have been stripped of their membranes. This ensures a balanced diet and helps maintain clean, fresh water. During the cultivation of carp fry, it's important to be aware of the challenges associated with the loop system, such as difficulty in draining and the risk of silt and organic debris settling inside. After 5–7 days, choose a sunny day and rotate the loop around 10 a.m. Eel fry tend to eat greedily, so it’s best to stop feeding bait fish 12 hours before the rotation to ensure the fry fast and reduce losses.
2. Net cage nurseries are considered ideal for raising young fish. They allow for a continuous supply of fresh water and abundant, easily accessible bait fish. However, there are some drawbacks: newly stripped bait fish cannot be immediately fed, and the cages require frequent cleaning and regular replacement. Managing fry in these cages can be complex and labor-intensive. Typically, a three-stage approach is used: Class I cages are made from 40–28 mesh polyethylene netting, sewn into boxes measuring 4–6 meters long, 1 meter wide, and 1 meter deep. Class II cages are slotted boxes made from 0.3 cm wide warp-knitted polyethylene mesh, sized 2 meters by 1 meter by 1 meter. Class III cages are similar but use 0.5 cm mesh. The ratio of these cages is usually 1:10:20.
3. Cement pools are commonly used for seedling rearing and typically measure 4 x 6 meters with a depth of 0.8 meters, though sizes may vary slightly. The bottom should have a slight slope to facilitate drainage, and a drainage pool must be located at the lowest point. Drainage systems usually consist of a rubber tube, a filter mesh, and supporting wire. The rubber tube is fixed at the center of the frame, ensuring it doesn’t interfere with the water level. The flow rate is controlled by adjusting the number of drain pipes and the height of the outlet, allowing for precise water management.
4. When carp fry grow to about 3.0 cm in length, they can be transferred to small earthen ponds for further growth. The stocking density is generally around 150,000 per hectare. Before introducing the carp, bait fish must be pre-cultured in the pond. Bait fry are usually introduced 10–15 days prior to the release of the main species, with a recommended density of 15–22.5 million tails per hectare. Fresh water should be added daily in small amounts to maintain good water quality and prevent deterioration.
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