The jellyfish have a high demand for food, and even when biological feed is introduced, it remains in short supply. This leads to low survival rates and smaller individuals, which directly affects the yield and profitability of the operation. This article focuses on artificial cultivation of biological feed, adopting a three-pool system: two pools for shrimp farming and one for jellyfish culture. The idea is to use shrimp ponds to cultivate large quantities of plankton, which are then drained into the jellyfish pond, creating an ecological balance and ensuring a stable food supply. This method provides a more abundant and sustainable environment for the jellyfish.
1. **Selection and Construction of Ponds**
Jellyfish should be raised in ponds that are easy to manage with good water inflow and drainage. The surrounding waters should be free from industrial pollution, and there must be access to freshwater to adjust salinity levels. The ideal size for each pond is between 0.67 to 1.33 hectares, with a length-to-width ratio of 4:1 and a depth of 2 meters. The pH should be maintained between 7.5 and 8.5. To ensure a balanced food supply, three pools are used: one for jellyfish and two for shrimp. A gate connects the shrimp ponds to the jellyfish pond, with a 40–60 mesh fence at the entrance to prevent unwanted organisms from entering. Water from the shrimp ponds is drained into the jellyfish pond through the middle section.
2. **Pond Preparation and Water Inflow**
2.1 For old ponds, dredging is necessary to remove organic waste and sediment. The pond should be flushed repeatedly by opening the floodgates.
2.2 On sunny days, quicklime or other disinfectants can be used to eliminate predators and pathogens.
2.3 When introducing water, a 40–60 mesh screen should be placed at the inlet to block harmful organisms. Water intake is best done between February and March, when harmful species are fewer. The initial water level should be kept shallow, around 30–40 cm.
2.4 Fertilization should occur on a sunny day at noon. Chicken manure combined with inorganic fertilizer is effective. Dilute the chicken manure before spreading it evenly to avoid sinking and rotting. Adjust based on water color.
2.5 Monitor water quality parameters such as pH, temperature, salinity, and plankton density. The process involves: water supply → fertilization → phytoplankton growth → zooplankton inoculation → sea bream development.
2.6 Inoculate rotifers and Artemia when phytoplankton reaches a certain density (transparency about 30 cm) and water temperature stabilizes at 18–20°C. Use newly hatched larvae for better results. The inoculation density ranges from 2000 to 1000 per cubic meter. Hatching eggs can also be used directly in the pond after determining their hatching rate and egg count.
3. **Stocking Seedlings**
3.1 Only healthy seedlings of 2 cm or larger should be used. Damaged ones must be discarded.
3.2 Stocking should take place between June and July, on calm days, in the morning or evening, when the water temperature is around 20°C.
3.3 Stocking density depends on the pond’s condition. A recommended range is 4500 to 7500 per hectare. High density may lead to slow growth and oxygen issues later.
3.4 Transport seedlings in smooth containers. For long-distance transport, use oxygenated, shaded, and cooled plastic bags to maintain stable temperatures.
3.5 Ensure water temperature and salinity in both nursery and growing ponds are similar before stocking. Transfer seedlings using boats and spread them evenly to avoid injury.
4. **Management During Cultivation**
4.1 After one week, gradually increase the water level by up to 10% to help young jellyfish adapt. Avoid sudden changes in water chemistry.
4.2 Monitor water color regularly. Dark brown or brownish green indicates healthy phytoplankton. If the water becomes lighter, add soymilk or soybean meal (2 g/m³ twice daily) to sustain algae. Re-inoculate if needed.
4.3 Before changing water, check external water quality for temperature, salinity, and biomass. Avoid drastic differences—salinity change should not exceed 5‰.
4.4 In the late growing season, drain water from the shrimp pond and refill with water from the adjacent pool. Add a 40–60 mesh net to allow small plankton to enter while keeping larger organisms out.
4.5 Continuously add fresh water to maintain salinity. Pump water near the fence first, then distribute it slowly across the pond.
4.6 Keep the water depth at 1 m initially, increasing to 1.5–2 m as the jellyfish grow. Maintain a stable water temperature between 20–28°C.
4.7 Observe feeding behavior regularly. If the jellyfish’s body appears transparent, it means food is scarce. Provide additional planktonic feed as needed.
5. **Harvesting**
Jellyfish grow rapidly, reaching 5–10 kg within 60–80 days. Growth slows when water temperature drops below 18°C, and they stop feeding at 15°C. At this point, harvest in batches, separating large and small individuals. Harvesting methods can vary, but draining the pond is a common and efficient approach.
6. **Conclusion**
The key to successful jellyfish farming lies in maintaining a steady supply of plankton. Effective water management and artificial feed cultivation are essential. Ultimately, the success of the cultivation period depends on monitoring and increasing plankton biomass. To sustain a healthy jellyfish population, maintaining optimal water conditions is crucial.
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