In 2003, we implemented a scientific feeding and management system using full-price compound feed. We conducted trials to raise and domesticate grass carp fingerlings in ponds for carp farming. The project involved eight acres of ponds, which yielded a total of 13,830 kg of large fish species. Among these, grass carp accounted for 2,900 kg, common carp for 8,600 kg, and white pelagic fish for 2,300 kg. The feed conversion rates were 2.0 for grass carp and 1.8 for carp. The survival rate of grass carp reached 75%, with a profit of 4,625.25 yuan per mu. This trial marked the initial exploration of domesticating grass carp in carp ponds, successfully addressing issues like disease and low fish quantity, while improving water utilization and overall aquaculture profitability.
**First, Pond Preparation**
1. **Pond Conditions**
We used an 8-acre pond at Lianyungang Kuangxiang Company Farm, with a depth of 2.5 meters. The water source was abundant, and the quality was excellent, with convenient drainage and irrigation. The pond was equipped with a 4-inch water pump, a 2.5 kW aerator, and a 90W feeder.
2. **Pond Clearing and Disinfection**
On April 22, we cleared the pond by removing excess silt, keeping the bottom silt at about 10 cm. We applied 100 kg of quicklime per mu to disinfect the pond, drained most of the water, and left about 10 cm of water. Small pits were dug at the bottom, filled with lime, and diluted into slurry. The mixture was evenly spread across the pond. On April 23, the mud was compacted with iron to mix the lime thoroughly.
3. **Water Addition**
After fertilizing the cleared pond on April 24, we added water to a depth of 0.6 meters, filtered through a 40-mesh sieve to prevent wild fish and harmful organisms from entering. We applied 400 kg of fertilizer per mu to maintain a transparency of around 25 cm.
**Second, Seed Stocking**
On May 2, we stocked 16,000 summer white carp at a density of 2,000 per mu. Two days later, we added 64,000 Jianou summer fish at 8,000 per mu. On May 10, we released 32,000 grass carp fingerlings at a density of 4,000 per mu.
**Third, Domesticated Culture**
1. **Domestication and Feeding**
We used a step-by-step method to domesticate both carp and grass carp. On May 11, we began domesticating the carp with crushed pellet feed, completing the process within a week. Grass carp were introduced on May 16, trained to feed along the pond edge using bran. Feeding started on May 18 using bamboo feed boxes. From May 20, floating compound feed was gradually introduced. The feed was crushed, and feeding was accompanied by sound-making to create a conditioned reflex. By May 26, the grass carp had developed a feeding habit. Feeding occurred twice daily, adjusting particle size based on fish size (0.5 mm to 4 mm). Feeding time was controlled at one hour per session. Carp and grass carp feeds were placed in separate ponds, 20 meters apart. Fish weight was measured every 10 days to adjust feeding amounts.
2. **Feed Requirements**
Squid were fed specialized feed with 34% protein. Grass carp received grain feed with 28% crude protein and 9% crude fiber. Before May 26, floating pellets were used; after that, matured feed was introduced. Crude fiber helped digestion and metabolism. Feed ingredients included fish meal (10%), soybean cake (20%), yeast (8%), rapeseed cake (10%), bran (30%), grass powder (10%), secondary powder (10%), inorganic salts (1.8%), and multivitamins (0.2%).
**Fourth, Breeding Management**
1. **Water Quality Regulation**
From May to June, new water was added every 10 days, 20 cm each time. From July to September, water was changed every 7 days, 30 cm each time. Aerator use was adjusted according to temperature and weather. In October, water changes were done every 10 days. Water remained “fat, live, tender, and cool†with a transparency of 20–30 cm and a greenish color. Lime was added every 15 days at 15 kg/mu.
2. **Disease Prevention**
Starting in August, we monitored water quality closely due to increased waste. After applying quicklime, we used Bacillus spp. to break down residues and reduce harmful substances like nitrite and ammonia. Proper measures ensured no fish diseases occurred during the breeding period.
**Fifth, Cultivation Results**
1. **Harvest**
Fish were harvested in late November, totaling 13,830 kg. Grass carp: 2,900 kg (6–10 kg per fish), survival rate 75%. Common carp: 8,600 kg (6–8 kg per fish), survival rate 94%. White pelagic fish: 2,330 kg (5–7 kg per fish), survival rate 90%.
2. **Economic Benefits**
Feed coefficients were 2.0 for grass carp and 1.8 for carp. Net profit per mu was 4,625.25 yuan, with an input-output ratio of 1:1.59.
**Sixth, Discussion**
1. **Cultivation Method**
Raising grass carp in carp ponds was previously considered difficult due to dietary conflicts. This experiment solved this issue through staged stocking and domestication, proving the method is effective and practical. It is recommended to place feed stations 15–20 meters apart for squid and grass carp.
2. **Feeding Strategy**
Using only pellet feed instead of green feed reduced water pollution and pathogen risk. Increasing crude fiber in grass carp feed (at least 9%) improved digestion and metabolism.
3. **Disease Prevention**
Preventive measures included thorough pond and fish disinfection, regular water treatment, and adding herbal medicine to feed. Allicin was used to prevent disease effectively.
4. **Stock Ratio**
The ratio of white carp to other species was set at 1:3, ensuring balanced growth and resource use.
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Zhoushan Junwei Aquatic Products Co., Ltd. , https://www.junweiaquatic-intl.com