Summary of high-yield two-season-per-year grass carp farming techniques, worth a look for farmers

Grass carp is one of the four major Chinese carps and is favored by the market, but its farming cycle is relatively long, and many farmers are reluctant to raise it. However, with current high-yield techniques, it is possible to achieve two harvests of grass carp per year. Below, let's take a look at the summary of high-yield two-season-per-year grass carp techniques.

I. Preparation before fish farming

1. Pond selection

Choose a pond with sufficient water sources, no pollution sources upstream, convenient drainage and irrigation, and a slight year-round water flow. The pond size should preferably be 0.2 ha to 0.67 ha, with a water depth of 1.5 m to 2 m.

2. Pond disinfection

10 to 15 days before stocking the fingerlings, disinfect the pond with water using 7 kg/667 sq m·m to 10 kg/667 sq m·m bleaching powder, or splash the entire pond with 75 kg/667 sq m·m quicklime mixed with water while hot.

II. Fingerling stocking

The first season starts around the Spring Festival, mainly stocking grass carp fingerlings, with appropriate mixed culture of bream, carp, silver carp, and bighead carp. Grass carp size 350 g/fish to 400 g/fish, stocking density 600 fish/667 sq m; bream size 200 g/fish to 250 g/fish, stocking density 500 fish/667 sq m; carp size 100 g/fish to 150 g/fish, stocking density 100 fish/667 sq m; silver carp size 300 g/fish to 400 g/fish, stocking density 100 fish/667 sq m; bighead carp size 150 g/fish to 200 g/fish, stocking density 20 fish/667 sq m, to ensure all can be harvested and marketed before the Dragon Boat Festival. The second season starts after the Dragon Boat Festival, stocking only grass carp fingerlings weighing 150 g to 200 g each, at a stocking density of 600 fish/667 sq m; by the end of the year, the average weight of each fish can generally reach more than 1.25 kg. Before stocking, all fingerlings are soaked and disinfected in a 4% saline solution for 10 to 15 minutes to prevent various bacterial diseases and saprolegniasis.

III. Feed feeding

1. Feed type. Use sinking pelleted feed specially for grass carp with a crude protein content of 28% to 30%. In the early stage of farming, the pellet diameter is 2.5 mm, and in the late stage of farming, the pellet diameter is 3.5 mm. The feed conversion ratio is 1.6.

2. Installation and use of the automatic feeder. This machine uses a 220 V single-phase lighting power supply, has a power of 90 W, a hopper volume of 80 kg, and a feeding area range of up to 80 sq m. The automatic feeder can be installed at the pond edge next to the management house, and the power switch is installed inside the management house. When feeding, simply turn on the indoor power switch, and the automatic feeder will evenly scatter the pelleted feed into the pond at set intervals according to the preset program. When feed feeding is completed (the feeding time for each meal is set to 1 hour), the power can be shut off automatically. For ponds within 0.67 ha, installing 1 automatic feeder is sufficient.

3. Feeding method. The feeding ability of fish is closely related to water temperature. When the water temperature is low, the feeding ability of fish is weak; when the water temperature is high, the feeding ability of fish is strong. Therefore, in the early stage of farming, the daily feeding amount is calculated at 2% to 3% of the total weight of grass carp, bream, and carp in the pond, and in the late stage of farming it is changed to 5% to 6%. In case of muggy weather, cold waves, heavy rainstorms, and other weather, the amount can be reduced as appropriate. Feed 2 times per day.

IV. Daily management

For high-density intensive production models, daily management work is mainly to maintain good, stable water quality, with the key focus on preventing oxygen deficiency and pond-wide fish kills.

1. Add fresh water. Persist in continuously adding water at a small flow rate day and night. In case of severe floating head, increase the water inflow.

2. Patrol the pond earlier. Mild floating head starts from 5 to 6 in the morning and disappears after the sun comes out at 7 to 8, which is a normal phenomenon. Severe floating head starts from 3 in the second half of the night. If measures are not taken in time, by 5 to 6 it will cause pond-wide fish kills. Therefore, at 3 in the second half of the night, one should get up and patrol the pond once, especially during the two solar terms Xiaoman and Mangzhong, when severe floating head is most likely to occur. If severe floating head is found, measures such as adding fresh water and turning on the aerator to increase oxygen should be taken in time to prevent pond-wide fish kills.

3. Turn on the aerator in a timely manner. For ponds under 0.67 ha, equipping 1 0.75 kW single-phase water-spraying aerator is sufficient. During mild floating head, it can be turned on from 5 to 6 in the morning until 8 to 9 when the floating head disappears, then turned off. During the two solar terms Xiaoman and Mangzhong, in case of thunderstorms or muggy weather, it should be turned on at 12 midnight until 8 to 9 the next day, then turned off.

V. Disease prevention and control

Adhere to the principle of "prevention first, prevention more important than treatment." During pond patrol, if grass carp are found gathering at the water inlet and the fish bodies appear black, this is a sign of disease onset. At this time, splash the entire pond with 1 mg/L bleaching powder for 2 to 3 consecutive days to stop the disease. During the second season of farming, disease generally does not occur. The main diseases in the first season of farming are the "three diseases" of grass carp and hemorrhagic disease.

VI. Timely harvesting

After 5 months of rearing, the various fingerlings stocked in the first season have basically reached commercial size, and all must be harvested and marketed before the end of May. At this time, it is around the Dragon Boat Festival, which is the off-season for fresh fish supply, and the market selling price is high. After another more than 5 months of careful rearing, the various fingerlings stocked in the second season reach commercial size before the end of December and must all be harvested and marketed.