Author: Lee Army 08-14 14:17:37
To quickly restore post-disaster aquaculture production and compensate for the shortage of fish seedlings, it is feasible to utilize autumn fish fry to raise species that will be cultured as adults in the future. Below are the key technical steps:
First, broodstock cultivation. Once the floodwaters recede, it's crucial to promptly clean and disinfect the ponds, then separate the broodstock. For optimal development, apply base fertilizers and regularly add liquid fertilizer or soybean paste. Grass carp and other species should be fed with green feed and supplemented with concentrated feed. During this period, water quality management and precise feeding are essential to promote gonad development.
Second, pre-breeding preparation. Autumn conditions can be challenging due to higher temperatures. Thorough planning is necessary throughout the breeding process, including checking gonad maturity, testing equipment, selecting cool weather, and ensuring experienced staff are available. If possible, use deep well water to regulate temperature effectively.
Third, hormone-induced spawning. For grass carp, use LRH-A (luteinizing hormone-releasing hormone analog), while eel and catfish may require HCG or a mix of hormones. After injection, keep the environment quiet. Maintain gentle water flow in the spawning pond. Begin flushing stimulation 2–4 hours before spawning and check the spawning net 6–10 hours later. If eggs are visible, proceed with artificial insemination. Apply chlortetracycline ointment to any wounds and administer penicillin or health supplements post-spawning.
Fourth, hatching management. The incubation water must be clean, filtered through a 40–50 mesh screen, with dissolved oxygen above 4 mg/L and pH between 7 and 8. Place approximately 200,000 fertilized eggs into a 200 kg incubator tank. Use a "high-low-high-low" flow pattern to ensure even egg movement. If large zooplankton like copepods appear, treat the water with trichlorfon at 0.2–0.5 g/m³. For early egg rupture, use potassium permanganate solution.
Fifth, fry transportation. Fry can be released when they develop a waist point, their yolk sac is nearly gone, and they start feeding. Transport them in 30–70 cm nylon bags filled with oxygen, with about 50,000 fry per bag. Avoid direct sunlight and high temperatures. Ensure the water temperature difference between the incubator, bag, and pond does not exceed 3°C.
Sixth, fry rearing. Before stocking, clean and disinfect the ponds, apply sufficient base fertilizer, and cultivate natural food sources. Stock 30,000–50,000 fry per acre. Initially feed them with cooked egg yolk in cages. Maintain thin water by grinding 3 kg of soybeans daily into pulp and feeding 3–4 times a day. Add fresh water to prevent floating heads. After about 10 days, when the fry reach 2 cm, perform several net exercises and transfer them to separate ponds.
Seventh, fingerling feeding. After passing through early stages, the fish grow to around 10 cm. Stock 3,000–5,000 fish per acre based on traditional polyculture ratios. In ponds with grasses and snails, prioritize feeding with duckweed or aquatic plants. In squid and shrimp ponds, apply organic and chemical fertilizers, along with bean cakes or cottonseed meal to accelerate growth.
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