Grass carp seedling health cultivation method
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Grass carp seedling cultivation requires careful planning and management to ensure optimal growth and survival. The pond should be approximately 5 acres in size, with a depth of 2 to 2.5 meters. It is recommended that the pond be oriented east-west to maximize sunlight exposure and maintain a quiet environment. The surrounding area should be free from tall trees or buildings that might block light or cause disturbances. The pond should have good lighting, ventilation, and easy access for fishing. The banks should be well-maintained, the dykes firm, and the bottom flat. A layer of silt about 10 to 20 cm deep is ideal, and the soil should be loam or sandy loam. The water source must be stable and reliable, and the pond should be equipped with complete infrastructure, including electricity, drainage, and irrigation systems.
Before stocking, the pond needs to be cleared and disinfected. Lime (150 kg per mu) or bleaching powder (4–5 kg per mu) can be used to adjust the pH and eliminate pathogens. Organic fertilizers such as chicken manure (200–300 kg), pig manure (400–500 kg), or horse manure (750–1000 kg) should be applied to enrich the pond bottom. These should be placed in small piles in the shallow areas of the pond.
Stocking density varies depending on the pond size. For grass fry, it is recommended to stock between 250,000 and 37,000 fish per acre. Carp seedlings (2500–3000 per acre), silver carp (1000–1500 per acre), and bighead carp (1000–1500 per acre) are also commonly stocked. Fry sizes should be between 2.5–3 cm, and stocking numbers can be adjusted if the pond is larger.
Water depth and quality control are essential during different stages of growth. Initially, the water depth should be around 0.7–0.8 meters. After 7–15 days, it should increase to 1 meter, then to 1.2 meters by day 20–30, 1.5 meters at 40–45 days, and 1.8 meters after two months. In autumn and winter, the depth should be maintained at 1.8–2 meters. Water transparency should be less than 30 cm when seedlings are released, and fertilizer should be added to maintain suitable conditions. During summer, transparency should be controlled at 25–30 cm, while in fall, it should be around 35 cm.
Water quality regulation is crucial. In the early stages, when fry are introduced, the water should be rich in nutrients, with transparency below 30 cm. As the fish grow, feeding strategies change. At 5–8 cm, the water level should be kept at 1.2–1.5 meters, with moderate feeding. At 8–10 cm, feeding decreases, and water is changed every 7 days. When fish reach 11–13 cm, more frequent water changes (every 5–7 days) help maintain water quality.
In later stages, feed amounts increase, so regular water testing and the use of photosynthetic bacteria (2 ml/m³ every 7–10 days) are important to maintain healthy conditions.
Feeding plays a critical role in grass carp cultivation. The feed should be nutritionally balanced, with crude protein ≥ 30%, fat ≥ 5%, fiber ≤ 8%, and ash ≤ 13%. Amino acid balance is essential, especially lysine, arginine, and phenylalanine. Animal and plant proteins should be in a 1:1.5 ratio. Fat content should not exceed 7%, and starch is the preferred energy source. Vitamins and minerals must be included in appropriate amounts, and non-nutritional additives like enzymes and attractants can improve feed palatability.
Feeding techniques vary by stage. Young fish (up to 5 cm) are fed 6 times daily, reducing to 4 times as they grow. Green feed is provided twice daily. The feeding rate decreases as the fish grow, from 20% to 15% initially, down to 3–6% for larger fish. Accurate estimation of survival rates helps determine the correct feed amount.
Disease prevention is key. Feed must be fresh and not spoiled. Regular removal of debris and dead fish is necessary. Vitamin C-rich green fodder should be used, with at least 600 mg/kg in formulated feeds. Feeding stations should be regularly cleaned with disinfectants. During disease-prone seasons, medicated bait should be used every 20 days, and the pond should be disinfected monthly with bleach or chlorine dioxide. Combining ecological and chemical prevention methods ensures long-term success.