Key Technical Points for Two-Stage Cage Culture of Mandarin Fish

I. Cage Structure and Setup

1. First-stage cage (breeding cage). Made of knotless netting, mesh size 0.5-1.0 cm, dimensions 10 m×1.3 m×1.5 m, quantity 3.

2. Second-stage cage (grow-out cage). Mesh size 1.5-2 cm, small-volume cages 3 units, dimensions 2 m×2 m×1.8 m; conventional large cages 3 units, dimensions 4 m×7 m×1.8 m.

3. Cage setup. Select a pond with an area of nearly 80 mu and a water depth of more than 2 m adjacent to the Qingtong River as the water area for cage placement, using an open floating setup, with bamboo frames as floats, and the cage body rising 20-30 cm above the water surface. The specific installation and fixing of the cages shall follow conventional procedures.

II. Main Technical Points

1. Fingerling stocking. In mid-May, first stock fry of the four major Chinese carps at 500,000-800,000 per mu as forage fish. When they grow to 1.5-2 cm, purchase 4,000 mandarin fish fingerlings with a body length of 3-4 cm on June 6 and place them in the first-stage cages at a density of 100 fish/sq m. After intensive rearing to 10 cm, release them into the second-stage cages, with stocking densities of 40 fish/sq m and 30 fish/sq m for small-volume cages and large cages respectively.

2. Fingerling rearing. Soak the purchased mandarin fish fry in 3%-4% saline solution for 10-15 minutes, then place them in the first-stage cages. Every day, seine and release forage fish from the rearing pond; their size should be about 50% of the body length of the mandarin fish fingerlings, and the quantity should be sufficient for the mandarin fish to feed to satiation. Conduct seine sampling at any time to check the feeding situation of the mandarin fish fingerlings so as to adjust the feeding amount in a timely manner.

3. Grow-out culture. In early July, place mandarin fish fingerlings of about 10 cm into the second-stage cages, using fingerlings reared in forage fish ponds as the main feed, and purchasing wild trash fish from the Qingtong River and other water areas for the shortfall. The size of forage fish should not exceed 50% of the body length of the mandarin fish, and the quantity ratio of the two shall be 1:20.

4. Fish disease prevention and control. Because mandarin fish only eat live fish throughout their lives, in terms of fish disease prevention and control, it is best to adopt a principle of prevention first, combining prevention and treatment. During the intensive rearing period of fingerlings, mandarin fish fingerlings are most susceptible to parasitic diseases. Therefore, every 5-7 days, select high-efficiency, low-toxicity deworming and sterilizing drugs and rotate them to soak and wash the fingerlings. During the grow-out culture period, every 7-10 days, use drugs in hanging bags for disinfection, and forage fish must be soaked and washed with drugs before being fed.

5. Daily management. Persist in inspecting the cages every day, checking whether the cages are damaged, whether forage fish are sufficient or insufficient, and changes in water quality, etc. Generally, wash the cages once every 10-15 days to maintain smooth water exchange inside and outside the cages.