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Artificial breeding of fry
Artificial Breeding of Fry
First, selecting broodstock is essential for successful artificial breeding. Choose 3rd to 5th instar fish weighing between 2.5kg and 3.5kg. During the non-reproductive season, males and females can be distinguished by their head shape and body color—males tend to have slightly wider heads and darker bodies, while females have narrower heads. In contrast, during the reproductive season, males develop larger muscle tumors on either side of their heads, and both sexes show visible gonads. Females have a round, concave genital opening, and their bellies are soft and swollen, appearing pale gray. The male-to-female ratio should be maintained at 3:2 to ensure optimal spawning conditions.
The broodstock are raised in ponds covering an area of 2500m² with a water depth of approximately 1.5m. Stocking density is around 20–30 per 667m². When the water temperature exceeds 13°C, special feed is introduced. At temperatures above 21°C, the feeding rate should be 2% to 4%, supplemented with animal-based feeds like boiled small fish or shrimp, as well as plant-based feeds such as malt. To stimulate gonad development, the broodstock should be rinsed once every 10 days.
For hormone stimulation, common agents include carp pituitary (PG), human chorionic gonadotropin (HCG), and luteinizing hormone-releasing hormone (LRH-A) and its analogues. For each kilogram of female fish, administer 4–6mg of PG, 1000 international units of HCG, or 2–2.5mg of LRH-A. A combination of PG and HCG can also be used, with 2mg of PG plus 600–700 international units of HCG. Male doses are halved.
To create suitable spawning environments, use plastic buckets, iron buckets, or wooden boxes as fish nests. Each nest should allow broodstock to enter and exit freely from one end, while the other end is covered with nylon cloth. After spawning, place the nests on the pond bottom, 3–5 meters from the edge, in water 0.5–1 meter deep, with the opening facing the center of the pond. Attach a float to the nest for easy location. Nests should be spaced 9–10 meters apart, and only 50% of the broodstock should be assigned to them.
When the water temperature is above 21°C, check the nests daily between 10am and 11am. Gently drive away the broodstock if eggs are present. Carefully remove the eggs and place them into a smooth barrel filled with pond water.
Egg hatching occurs optimally at 25°C–29°C, with fertilized eggs taking about 110–120 hours to hatch. Larvae typically develop into juveniles within 10 days. Eggs can be naturally hatched in ponds or in hatching tanks. Incubation requires a water temperature of 25°C–28°C, a pH level between 6.5 and 8.0, and dissolved oxygen of at least 6 mg/L. Water exchange should be around 20 liters per minute.
To prevent fungal infections, alternate between mildewin and formalin treatments. Before the eggs turn red, apply the treatment once daily. Use water mold net at a concentration of 60–65mg/L for 10–12 minutes, followed by formalin at 100mg/L for 4–10 minutes. This helps maintain high hatching success rates and ensures healthy fry development.