What is the appropriate stocking density for grass carp? Scientific stocking is the key
Summary: For grass carp fingerlings generally around 200-250g in size, the stocking density should be kept at about 300 fish/mu. To improve farming efficiency, grass carp are usually polycultured together with other fish species. Generally, crucian carp fingerlings at 15-20 fish/kg are stocked at 300 fish/mu, silver carp fingerlings at 5-6 fish/kg are stocked at 50 fish/mu, and bighead carp fingerlings are stocked at about 10 fish/mu.
For fingerlings 200-250g in size, the stocking density is generally about 300 fish/mu. Since the grass carp farming cycle takes about 3 years, with relatively high costs and a long time investment, in order to make reasonable use of the farming water surface and increase returns, farmers now generally adopt a polyculture model of raising grass carp together with other fish species.
1. Pond requirements
The area is best kept at about 10-20 mu, the water depth maintained at 2-2.5m, and the silt at the pond bottom should not exceed 20cm in thickness. To ensure sufficient oxygen in the water and even feeding of bait during the farming process, each 10 mu of pond needs to be equipped with one 3kw aerator and one automatic feeder.
2. Pond preparation
In winter, drain the water from the pond and let it freeze and dry in the sun for about 20 days. Half a month before stocking the fry, fill the pond with about 10-20cm of water and splash quicklime into the pond at a ratio of 150 kg/mu for disinfection.
3. Stocking fingerlings
Stocking is generally chosen around the Spring Festival. Before stocking, soak the fingerlings in 5% salt water for disinfection for about 10 minutes. Grass carp fingerlings around 200-250g in size should be stocked at a density of about 300 fish/mu, crucian carp fingerlings at 15-20 fish/kg at 300 fish/mu, silver carp fingerlings at 5-6 fish/kg at 50 fish/mu, and bighead carp fingerlings at about 10 fish/mu.
4. Feed feeding
Mainly feed pelleted feed, requiring the protein content in the feed to be about 28-32%. To ensure adequate nutrition for grass carp feeding, green grass feed should also be fed in combination. When feeding, adhere to the principles of “coarse first, fine later” and “four fixed, four observe”, feeding once each morning and evening every day, with the feeding amount best being what can be finished within 2 hours and with the grass carp eating to 80% full. From March to June, mainly feed pelleted feed with 28% protein content and appropriately feed some green feed, with the daily feeding rate kept at about 3%; from July to September, to control disease in the fry, reduce the feeding rate of 28% protein pelleted feed to about 1.5% and increase the feeding of green grass feed; from October to November, after continuously feeding 32% protein pelleted feed for a period, stop for about one week, and during the interval some raw grain feed can be fed.
To prevent grass carp from being infected with hepatobiliary syndrome, some vitamins and other drugs can be appropriately added to the feed during daily feeding to prevent disease and reduce the probability of death from fish disease.
5. Water quality management
From June to October, on sunny days, turn on the aerator for two hours from 1 pm to 3 pm every day, and in the early morning oxygen can be appropriately added to the pond. During consecutive overcast days, the aerator should be turned on earlier. Regularly add new water to the pond, slowly regulating water quality according to the method of “small drainage, small intake, multiple water changes”; from June to September, add new water to the pond once about every 3 days, each time adding about 10cm of water, and every half month splash quicklime into a pond with 1m water depth at a ratio of 10-20 kg/mu for disinfection.
6. Disease prevention
When feeding, follow the standard of “coarse first, fine later, combining coarse and green”. In daily management, prevent grass carp from being infected with hepatobiliary syndrome. In addition, red-skin disease, gill rot disease, and enteritis disease are also common diseases of grass carp. Treatment can generally be carried out by oral administration and external splashing. Oral administration mainly refers to feeding grass carp medicated bait with “Sanhuang powder”. Sanhuang powder is made by grinding 50% rhubarb, 30% phellodendron, and 20% skullcap into powder and stirring evenly. For every 50kg of fish, the feeding amount is 0.3kg of Sanhuang powder mixed evenly with flour paste, then mixed evenly with the feed and fed continuously for 3-5 days; external splashing is simply splashing a certain proportion of bleaching powder, chlorine dioxide, and other disinfectants into the pond for 3 consecutive days.
7. Timely harvesting
To reduce the carrying capacity of the fish population in the pond and promote the rapid growth of small-sized fry, the large-sized adult fish in the pond that have reached market standards should be caught and sold in a timely manner, which can increase yield to a certain extent. Generally, one harvest is carried out at the end of July in the morning when the water temperature is lower.