Techniques for raising field crabs

(Baonghean)Field crabs are a familiar aquatic species, closely associated with our farmers from the past to the present. Crab farming is a new profession that is very attractive to people and has a lot of potential. Crabs live in the wild, have very few diseases, but when raised at a higher density than in the wild; some technical measures are also needed to achieve high economic efficiency.

Here is an introduction to the crab farming model in ponds and rice fields; depending on the specific conditions of each household, we apply:

Prepare ponds and fields for farming:

Water source must be proactive and unpolluted.

There are separate water supply and drainage systems.

The best pond bottom is loam, with a 20cm thick layer of mud.

The pond has an area of ​​300-1,000m2, depth of 0.8-1.2m.

Around the bank must be fenced with bamboo, plastic sheet or fishing net placed at an angle towards the pond to prevent crabs from escaping.

For farming fields:

- The farming area should be from 1/3 to 2/3 hectare, the field must be flat. The best soil quality is loam.

Design and construction of aquaculture fields:

- There must be a fence around the edge of the field to prevent crabs from leaving the field. The fence can be made of Fibro-cement or rubber tarpaulin, the fence must be at least 40cm high from the edge, the fence should be tilted towards the field to prevent crabs from escaping.

- Digging ditches for farming: there are two ways:

Dig ditches to raise crabs in the corner of the field, the ditch area is 5% of the field area, the ditch is 4-6m wide and 1 - 1.5m deep.

Dig a surrounding ditch and a central ditch.

Total area of ​​ditches is equal to 15-20% of field area.

All drains must be covered with bamboo nets or suitable fishing nets, and the drains must be compacted to limit crabs from digging burrows.

Pond and field improvement:

1-2 weeks before raising, drain the water to kill all crab pests and pathogens by applying 7-10 kg of lime per 100 m2, drying in the sun for 3-5 days, then adding water to the pond. For rice fields, add water but do not let the water overflow into the fields. Only when the rice is about to form panicles, add water to the fields so that the crabs can go up to the fields to find food.

- Use manure or chemical fertilizers to color the pond water to create a source of zooplankton to grow as food for newly released crabs.

- In ponds and fields, you should use mulch as a shelter for crabs when they molt to avoid loss. You can also add duckweed, water spinach, water coconut vegetables, etc. to cover the pond on hot sunny days. Coverage should be about 1/3 of the pond surface.

Select and release seeds:

- The stocking season is usually from February to April every year.

- Choose healthy, disease-free, fully developed claws and legs, bright color, and no algae. You can choose male crabs to raise to help increase productivity and commercial value.

- Density: pond farming: 10-15 fish/m2, rice field farming: 5-7 fish/m2.

- When releasing crabs, we should not release them directly into the pond but from the edge of the pond so that they can crawl down to the pond or field to avoid environmental shock.

Crab care:

- Crabs' food is very diverse, with a focus on animals including trash fish, snails, mussels, sweet potatoes, cassava... Food should be chopped into small pieces to fit the crab's mouth size.

- Food ration is 5-8% of crab weight/day and divided into 2 times a day, early morning 20-40% and afternoon 60-80% of body weight. Food must be fresh, not spoiled or moldy.

- Crabs need to be fed just enough food to ensure water quality, help crabs digest food well, limit food waste, and reduce farming costs. In the pond, it is necessary to arrange some feeding trays to assess the crab's prey situation and at the same time, based on weather conditions, adjust the amount of food accordingly.

Crab management:

- Regularly change water in ponds and fields about once a week to stimulate crabs to molt and catch prey strongly. Each time, change 1/4-1/3 of the water in the pond or ditch.

- Periodically add lime to the pond every 15 days with a dosage of 2-3 kg/100m2 mixed with water, take the clear water and sprinkle evenly throughout the pond.

- Regularly check sewer barriers and fences to prevent crabs from escaping.

Crab harvest:

- When the crabs reach commercial size and fetch a high price, they can be harvested.

- Harvest by setting traps, covering, draining, catching by hand if harvesting completely.

- Small crabs that are not of commercial size are kept to be raised for the next crop.

Vu Xuan Nam