Pond Culture
(1) The conditions and requirements for aquaculture ponds are essential for successful fish farming. Adult ponds typically range from 5 to 10 mu, with an ideal size of 3 to 5 mu. The water depth should be between 1.5 to 2.5 meters. Sandy loam soil is the best choice for pond construction. Water quality parameters are crucial: dissolved oxygen levels must remain above 6.5 mg/l, ammonia concentration should not exceed 0.3 mg/l, and the pH level should be maintained between 7.5 and 8.5. These factors ensure a healthy environment for fish growth.
(2) Before stocking, it's important to prepare the pond properly. This includes sterilizing the pond and refilling it with fresh seawater following standard marine aquaculture procedures. Fertilization of new water should begin 7 to 10 days before planting to promote plankton growth. A pre-drainage of 70-80 cm helps raise water temperature more quickly, which is beneficial for early fish development.
(3) Fish stocking specifications and density play a key role in maximizing yield. The ideal weight for fingerlings is between 1.9 and 4.3 grams. Stocking density is usually around 1,500 per mu, ensuring enough space for growth without overcrowding.
(4) During the cultivation period, regular monitoring is necessary. Water quality should be strictly controlled, and any issues should be addressed promptly. Feeding should be done at a rate of 2-5% of the fish’s body weight daily, typically twice a day—once in the morning between 8-9 am and once in the afternoon between 3-4 pm. Feeding should be consistent, timely, and measured. Maintaining the water level at about 2 meters is important, with a daily water exchange of 20%. Regular cleaning of the pond area, removal of weeds, macroalgae, and leftover feed is also necessary. Medications should be used periodically for disease prevention, and any signs of illness should be investigated and treated immediately. Keeping detailed records of all activities is essential for effective management.
Cage Culture
(1) Stocking specifications and densities vary depending on the stage of fish development. Redfish cage culture can be divided into two stages: the mid-cultivation phase for seedlings and the growing phase. For the mid-cultivation stage, fingerlings should be around 2.5 cm in length. At temperatures between 23-28°C, they can grow to about 6 cm within 30-40 days. The maximum stocking density for this stage is 1,500 per cubic meter. In the growing phase, fish that are 6 cm long should be stocked at a density of 60-100 per cubic meter, ideally 20-30 per cubic meter to allow for proper growth.
(2) Daily cage management involves careful attention to safety and feeding practices. Regular inspections of the cages are necessary to prevent fish from escaping. Records should be kept of feeding schedules, fish activity, water temperature, salinity, weather changes, and fish growth, which should be measured every 10-15 days. Any damage to the cage should be repaired promptly to maintain its integrity.
(3) Removing attachments from cages is an important maintenance task. Algae, bryozoans, sponges, ascidians, and sediments often accumulate on the cage structures. Manual cleaning or the use of high-pressure water guns and submersible pumps is recommended to effectively remove these materials. It is important to clean the cages thoroughly rather than simply replacing them.
Feeding
There are two main types of feed used in aquaculture: small trash fish and compound feed. When using trash fish, freshness is critical to ensure the health of the fish. The daily feeding amount should be 2-5% of the fish’s body weight, and feeding should occur twice a day to support optimal growth and digestion.
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