Grass carp are fish with wide adaptability to environmental conditions, they can live in hermaphrodites. Grass carp live mainly in the middle and lower water layers, where there are many aquatic grass near the shore, the fish’s main food is plants such as water grass, molluscs, dogtail algae, shrimp seaweed, duckweed. , dandelion flowers. To achieve the best yield when harvesting, farmers need to understand grass carp farming techniques from someone with experience. The content of the article below will help you get more information on this topic.
The pond area from 400 to 1000 m2 is the most suitable.
The pond must be clear, not smothered by the police, the pond bank must not leak, the pond bottom is flat with a layer of mud about 15-20cm thick.
The water level in the pond ranges from 1 to 1.2m, too shallow or too deep water affects the growth of fish.
The water supply to the pond must be clean, unpolluted by waste sources, domestic wastewater, wastewater from factories in industrial zones, pH 6.5 – 7.5 dissolved oxygen content. dissolved, maintained from 34mg/l.
Preparing the pond
After each crop, draining is done, clearing grass, cultivating shoreline, dredging mud (if the amount of mud is too much, it should be dredged, leaving only a layer of mud of 15-20cm).
Apply lime to kill trash fish and pathogens. The amount of lime applied is from 7-10kg/100m2 of pond bottom.
How to apply: Lime is sprinkled evenly on the pond bottom and the banks, then dried in the sun for 2-3 days before adding water to the pond.
Taking water to the bottom of the pond: the water taken into the pond must be filtered through a net or a net with small eyes to release wild fish and trash fish from entering the pond.
Use 20-30kg of manure to fertilize 100m2 of ponds 2-3 days before to prepare to release fish.
Release of fingerlings
Time to release fish fry
Spring crop from February to March.
Harvest from August to September.
Standards of fingerlings: choose the same large size fingerlings from 10-15cm/fish, the fingerlings must be healthy, have complete scales, no loss of slime, uniform size and no disease.
Stocking fingerlings from 2 to 3 fish/1m2 of pond.
After being transported from the hatchery to the pond, the fingerlings must get used to the new water environment before stocking by soaking the transport tool in the pond for 5-10 minutes, then opening the tool and letting the fish grow up. The pond water slowly comes in with the same amount of water as the existing water and slowly release the fish.
- It is recommended to bathe the fish before releasing it into the pond with table salt diluted with clean water, the dosage is from 2 to 3%, the time is from 5 to 10 minutes.
- People should buy fingerlings at reputable establishments, licensed by the state to operate to ensure the quality of fingerlings.
- Fish should be released in the morning or in the cool of the afternoon to achieve a high survival rate.
Care and management of ponds
Green food includes grasses, seaweed, duckweed, water hyacinth, banana leaves, cassava leaves. It is recommended to feed the fish enough daily to ensure good growth of the fish.
In the early stages, foods such as grass leaves, cassava, banana stalks, corn leaves, banana leaves need to be chopped to fit the mouth of the fish.
When the fish reaches 0.8kg/head or more, the fish can be fed directly with grass, cassava leaves, banana leaves, and the banana stem still has to be chopped.
After each feeding, it is necessary to check and dispose of grass stalks, trees, and old leaves that are not eaten by fish to avoid contaminating the water in the pond.
The amount of grass, cassava leaves, fresh corn leaves fed from 30-40% of the weight of fish stocked in the pond/day. With seaweed, water hyacinth, banana trees feed 60% of the weight of fish stocked in the pond/day.
Concentrated feed, homemade feed, rice bran, corn bran feed the fish with a diet of 1.5-2% of the fish weight in the pond.
Industrial feed now has types such as stork code from 8001 – 8008, goldfish code from 632 – 636 depending on the size of the fish. Use according to the manufacturer’s instructions on the packaging.
Regularly monitor pond banks, drains, see pond water levels every morning to take remedial measures if problems occur.
In the early morning, if the fish is floating, the long head does not dive, then stop feeding and pump more water into the pond or use a sprayer to reverse the water in the pond to increase the oxygen content.
Periodically every month, use powdered lime diluted with clean water to spread evenly over the pond surface with a dosage of 2kg/100m2 of pond.
Prevention and treatment of some common diseases for farmed fish
In the process of raising grass carp, we often suffer from some of the following diseases such as red spot disease, hemorrhagic disease, anchorworm.
This is one of the infectious diseases causing great damage to productivity and production.
When newly infected fish often reduce their appetite, stop eating, swim sluggishly on the surface of the water around the pond in the morning. On the body of the fish appear red sores, scales fall off.
Fish with severe disease have hemorrhagic fin roots, fin rays are torn off gradually, scales fall off, red spots hemorrhagic, inflammation and ulcers widen deep into the body causing stench, around the sores there are fungi, parasites, bulging and opaque ankles, anal inflammation, swelling, bleeding, and distended abdomen.
When fish are infected with red spot disease, it is very difficult to treat, so integrated disease prevention is very important.
How to prevent red spot disease: Using drug KN-04-12 of the Institute of Aquatic Environment for feeding to prevent disease. As for sick fish, only those who still eat food can cure the disease.
This is a dangerous disease commonly found in grass carp caused by a virus causing great losses to producers. Currently, there is no cure, so people need to pay attention to prevention from the very beginning.
Dead fish due to haemorrhagic disease show whole body intact, also known as beautiful dead fish. Before the fish died, the fish stopped eating, swimming slowly, some of the fish turned black, when peeling off the scales, the muscle layer under the skin was bleeding or when the fish was brought into the dark, using a flashlight to see the whole body was red, dissecting to observe the internal organs. The intestines were found to be intact, without food, and the surface of the internal organs was bleeding. When the fish is sick with a high rate, it is most effective for fish of commercial size, so people should collect and sell it, and for small fish, drain it to clean up the pond.
When infected with parasitic anchors, in addition to sucking nutrients from fish, they also ulcerate the skin, fins, and gills, creating conditions for other parasites such as fungi and bacteria to invade and cause disease.
Common symptoms in fish appear red spots, bleeding, ulcerated areas on the body of fish, fish are often thin and weak, large heads, gradually losing normal color, sluggish swimming, poor response to humans and harmful organisms.
To prevent and treat the disease, fresh Xoan leaves can be used in bundles, pounded and dropped into sick fish ponds with the amount of 30-50kg leaves/100m2 of water.
Pay attention in the first few days because of the strong decomposition of Xoan leaves, leading to a lack of oxygen, which can make fish float slightly. Decomposed leaves have the effect of making phytoplankton thrive and limit the growth of wheelworms.
After 7-8 months of farming, it is possible to prune the large number of fish and release the same-sized fingerlings to increase the productivity.
At the end of the whole fish season, small fish can be selected to keep as seed for the next crop.
With the above farming process, after 10-12 months of farming, the harvested fish size is 1.5-2kg/fish. Survival rate is from 60 – 70%, yield is from 12 – 42 tons/ha.
Above is the technical process of raising grass carp, wish you and your friends to apply it successfully