Abstract
In China, broodstock conditioning of grass carp (Ctenopharyngodon idella) is conducted in earthen ponds at a density of 2,250 - 3,000 kg ha-1 and at a male to female ratio of 1:1 or 1:1.25. Vegetation such as duckweed and rye grass and small amounts of farm-made or commercial feed are given. Nursing from fry to fingerlings (early nursing) is done in nursery ponds at a density of 1,500,000 - 2,250,000 fish ha-1 (150-225 m-2). After nursing for 20-30 days, the fish reach 3-4 cm in length and are released into fingerling nursery ponds for advanced nursing. Fingerlings are stocked in fingerling nursery ponds at a density of 3,250-4,000 fingerlings ha-1 (0.325-0.40 m-2). The main feed is pellet feed and grass. After 6 months of culture, the fish can reach 800 g. Then they are released into grow-out ponds or cages. Stocking rates for ponds are 1,650-2,000 fish ha-1 (0.165-0.20 m-2) and 50-80 fish m-2 for cages. Mixed feed is used as the main feed and grass is given as supplementary feed. The fish can reach 1.5-2.0 kg in 1 year and 3.5-5.0 kg in 2 years.