CATDOLL : CATDOLL: Seeking crab farming technology

1. Choose a good pond: The crab pond conditions are sufficient water source, good water quality, convenient water inlet and outlet, the area is generally 1-5 mu, and the water depth is generally 1-1.5 meters. The best quality of the crab pond bottom is sandy loam and gravel soil, which has good ventilation performance, is conducive to the growth and reproduction of aquatic plants and benthic plants and animals, and can provide natural feed for river crabs. The thickness of the silt at the bottom of the pond is generally not more than 5 cm. Anti-escape facilities should be built around the crab pond, such as brick walls, plastic films, etc. The inlet and outlet of the crab pond should be blocked with wire mesh to prevent river crabs from escaping.

2. Preparation before stocking: Before stocking young crabs, the crab pond should be cleaned and disinfected and aquatic plants should be planted. The method of cleaning the pond is to drain the water, expose the bottom of the pond to the sun, and disinfect it with quicklime or bleaching powder. This is very effective. It is very important to remove frogs or frog eggs at any time. The stocking density of crab seedlings is generally about 800-1000 per mu. Aquatic plants such as bitter grass and water hyacinth can be planted. First, they can provide feed for young crabs, and second, they can provide young crabs with a sheltered habitat, which is conducive to the growth of river crabs.

3. Scientific feeding and careful management: In the whole process of pond farming, river crabs mainly rely on artificial feeding, in addition to using aquatic plants and benthic organisms. Since river crabs are omnivorous animals, we mainly feed them with fish, shrimp, cakes, potatoes, wheat and other feeds. When feeding, put the bait on the soil slope close to the water level or in shallow water. Generally, 3-5 evenly distributed feeding points are selected per acre of water surface, which is convenient for observing the feeding and activity of river crabs and is conducive to removing residual bait. The feeding time is to adapt to the habit of river crabs hiding during the day and coming out at night. It can be selected around dusk, once or twice a day, and it should be moderately controlled according to the situation. River crabs have higher requirements for water quality conditions than fish, especially they are more sensitive to polluted water bodies. Good water quality in the pond is conducive to the growth and development of river crabs, and the meat is delicious. The pH value of pond water for crab breeding should be 7-9, and the optimum is 7.5-8.5. The dissolved oxygen in the pond water should be kept above 5 mg/L. If it is lower than 5 mg/L, it will affect the growth and development. If it is lower than 2 mg/L, it will cause the death of river crabs. In order to keep the water fresh, it is generally necessary to change and add water frequently to keep the pond water clear, fresh and alive, and the transparency should be above 40 cm.

4. Prevention and control of pests and diseases

The main enemies of river crabs are water rats, frogs, and birds, among which water rats are the most harmful. River crabs move around the slopes of ponds at night, especially soft-shell crabs that have just shed their shells. They often move slowly for several days and are most vulnerable to attacks. Prevention and control methods include poisoning with bait and artificial capture.

There are several common diseases of river crabs. In the fry and juvenile stages, there are constrictors and monoconstrictors. In severe cases, they affect the normal activities and feeding of the juveniles. In the juvenile and adult stages, there are crab slaves and red filaria. The former parasitizes in the abdomen, and there are white spots in the navel of the crab. In severe cases, the meat smells bad and is inedible. The latter parasitizes in the body and is visible to the naked eye. In addition, there is shell dissolution disease, that is, holes in the crab shell; black spot disease, black spots on the crab body.

Once river crabs are sick, it is difficult to cure them. Therefore, we should prevent them before they are sick. Prevention is the main approach. Before releasing river crabs, we should thoroughly clean the pond, disinfect it, and kill the germs. During the breeding process, we should frequently add new water and sprinkle quicklime, which can achieve better results.

Five key measures

1. Be careful when casting bait

The bait should be mainly high-quality granular feed, fresh ice fish and soybeans. Try not to feed powdered feed to reduce water pollution. The feeding should be increased or decreased appropriately according to the seasonal weather, the growth and activities of the crabs, etc. During the molting period of the crabs, nutritional additives should be added to the feed to ensure the normal molting and growth of the crabs.

2. Early drying of the pond

The pond is usually dried in January every year. After drying, the pond side is silted and the bank is repaired. The pond drying time should not be too long, generally 10-15 days is appropriate, and it only needs to be slightly hard. This will reduce damage to aquatic plants and benthic organisms in the pond and maintain the original ecology of the pond.

3. Densely planted grass

In the early stage, it is required to plant more grasses at the pond mouth and plant enough grasses. In the middle stage, the grasses should be well managed: First, the water color is too dark to affect the photosynthesis of water plants, and water should be adjusted in time. Second, the water quality is turbid, and pollutants attached to water plants should be removed in time with water purification biological agents. Third, water plants wither and lack of activity should be fertilized in time. In the later stage, the coverage of water plants on the pond surface should be controlled at about 60%, and the old grass heads of water plants exposed on the water surface should be cut off to allow river crabs to grow healthily in a good ecological environment.

4. Snails

Use multiple releases to prevent a large amount of snails from being released at once, which would cause the water quality to be clear and moss to grow in large numbers in the early stages. Release a batch of snails before the Qingming Festival, at a rate of 300 catties/mu, and gradually add more snails by the end of June, at a rate of 500 catties/mu. This will regulate the water quality of the pond, facilitate the natural proliferation of snails, and ensure that there is sufficient natural live bait in the pond in the middle and late stages of aquaculture. [1]

5. Water regulation

August is a high temperature period and a season change stage. In order to properly reduce the temperature in the water body and minimize the temperature difference, the pond should maintain the highest water level, add water and change water frequently, add new water every 2-3 days, change water every 7-10 days, add water in the early morning or morning, and do not add water in the evening. Use microbial agents regularly every 7-10 days to regulate the water quality and keep the water fresh at all times, so as to reduce casualties of river crabs in the high temperature season and ensure the survival rate.