Author: Lee Army 08-14 14:17:37
To quickly restore aquaculture production after a disaster and compensate for the shortage of fish seedlings, it is feasible to use autumn fish fry to rear fish species for future adult farming. Below are the key technical steps:
First, broodstock management. Once the floodwaters recede, it's crucial to promptly clean and disinfect the fish ponds and separate the broodstock. For broodstock cultivation, apply base fertilizers and feed them regularly with green feed, supplemented with concentrated feed as needed. During this period, water quality must be strictly controlled, and feeding should be fine-tuned to promote gonad development.
Second, pre-breeding preparation. Autumn fish breeding can be challenging due to high temperatures. All preparations must be thorough. The entire breeding process needs careful planning, including checking gonad development, ensuring breeding equipment is ready, selecting cooler weather, and assigning experienced staff. If possible, use deep well water to regulate temperature.
Third, hormone-induced spawning. For grass carp, use luteinizing hormone-releasing hormone analogs (LRH-A), while for eels and other species, human chorionic gonadotropin (HCG) or a mix of A and B hormones can be used. After injection, keep the environment quiet. Maintain a gentle water flow in the spawning pool. Begin flushing stimulation 2–4 hours before spawning and check the net every 6–10 hours. If eggs are visible outside the abdomen, artificial insemination can proceed. Post-spawning broodstock should be treated with chlortetracycline ointment and given antibiotics or postpartum care agents.
Fourth, egg incubation management. The incubation water must be clean and free from pollution, filtered through a 40–50 mesh screen. Dissolved oxygen should stay above 4 mg/L, with a pH between 7 and 8. Place about 200,000 fertilized eggs into a 200 kg incubator tank. Adjust the water flow according to a "high-low-high-low" pattern to ensure even egg rotation. If large zooplankton like leeches are present, treat the water with 0.2–0.5 g trichlorfon per cubic meter. If eggs rupture prematurely, treat with potassium permanganate solution.
Fifth, fry transportation. Fry can be transported when their yolk sac is nearly gone, they have a visible waist, and they can start feeding. Use oxygenated nylon bags measuring 30–70 cm, each containing approximately 50,000 fry. Avoid high temperatures and direct sunlight, and ensure the temperature difference between the incubator, transport 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 raise them in cages and feed them with cooked egg yolk. Keep the water thin, using 3 kg of soybean pulp per acre, fed 3–4 times daily, and add fresh water to prevent floating heads. After about 10 days, when the fry reach 2 cm in size, perform several net exercises and transfer them to separate ponds.
Seventh, fingerling feeding. After being raised in early ponds, fry are gradually introduced to larger areas and fed to grow to around 10 cm. Stock 3,000–5,000 fingerlings per acre based on conventional polyculture ratios. In ponds with grass carp, provide as much duckweed or tender grass as possible. In ponds with carp and other species, apply organic and chemical fertilizers and supplement with bean cake or cottonseed meal to accelerate growth.
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