Detailed Explanation of River Crab Farming Methods and Key Points of Daily Management

River crab is also called "crab" and "hairy crab". Its carapace, formed by the fusion of the head and thorax, is squarish-round and hard in texture. River crab is a poikilothermic crustacean, and its suitable water temperature for growth is 15-25°C. Doing a good job in the farming management during the river crab growing period can improve river crab quality and yield and increase farmers' income.How are river crabs farmed? What are the key points of daily management?

I. How are river crabs farmed?

There are many ways to farm river crabs. Take lake pen-enclosure crab farming as an example:

1. Pen-enclosure construction

Use a double-layer pen enclosure, with the two layers of net 5m apart. Fix bamboo poles (or tree trunks) around the pen enclosure as anchoring stakes, with 2-3m between each stake. After sewing the cut polyethylene netting, bind it to the stakes with rope, stretching it up and down, left and right into a flat surface. Fix the bottom of the net with stone cages and ground anchors so that the net foot fits tightly against the bottom mud, with the stone cages pressed 20cm into the bottom mud. The upper part of the net should stand 1-1.5m above the water surface, and a "T"-shaped net piece should be installed on top. On the upper edge of the net, set a net brim made of 30-50cm vertically downward plastic film, and keep it tight against the net.

2. Planting grass and putting in snails

After the pen-enclosure facilities are built, use an electric fish catcher to clear out large predatory fish in the farming area. In February-March, plant Elodea, using 2-3kg of grass stems per sq m, bundling them into several bunches and treading them into the lake-bottom mud. In about 1 month they will take root and grow and become luxuriant. At the same time, transplant several plants of sedge and reed and other emergent plants, and transplant water peanut communities on the water surface covering about 1/5 of the total area. Before Qingming, put live snails into the pen enclosure, 500kg per mu. This creates a good ecological environment for crabs and fish and provides high-quality natural bait.

3. Seedling stocking

Crab seed stocking is carried out 1 month after planting grass and putting in snails, or a small area can first be enclosed to put the crab seeds in earlier. The associated fish species are stocked in May-June. The stocked crab seeds are disinfected by medicated bath with potassium permanganate or table salt, and the fish species with bleaching powder or trichlorfon and other drugs for 10-30 minutes. Select authentic high-quality "button crabs" from the Yangtze River system, requiring uniform size, about 160 per kg, with the stocking amount per mu controlled within 600. At the same time, 6-9cm mandarin fish and 2-3cm yellow catfish large-size seedlings can be stocked together, with stocking amounts per mu of about 20 fish and 50 fish respectively.

4. Feed feeding

Regularly supplement water grass and snails so that the crabs mainly feed on natural bait. In the early stage, in order to allow the snails to reproduce and grow, some fresh snail and mussel meat and small trash fish can be appropriately fed. In the later stage, feed once a day with bait made from pumpkin, shredded potato and fresh fish, fishmeal, soybean cake and soybean, to supplement the nutritional deficiency of natural bait and ensure the crabs are plump and strong. The feed fed should be fresh, palatable, not moldy, rotten or deteriorated. Leftover bait should be promptly removed to avoid spoiling the water quality.

II. Key Points of Daily Management in River Crab Farming

Whether daily management work is done well directly affects the economic benefits of river crab farming. In management, the following points should be achieved:

1. Regularly inspect and reinforce the anti-escape facilities. Especially in the rainy season and when it is windy and raining, inspection should be strengthened even more to strictly prevent the anti-escape facilities from being blown down by strong winds, the pond ridge from being damaged by heavy rain, and the pond from being flooded, so as to prevent river crabs from escaping.

2. Persist in inspecting the pond morning and evening. In the morning, mainly check whether there is leftover bait in the pond, so as to arrange the bait amount for the day, and clean the feeding ground, remove the leftover bait, and create a clean feeding environment. At the same time, observe the pond water quality to decide whether water needs to be changed or the pond water needs to be improved. In the evening, inspection mainly observes the river crabs' activity, feeding and growth, and problems found should be promptly adjusted in the feeding and management measures.

3. Regularly check whether the pond ridge leaks and whether the anti-escape nets at the inlet and outlet are intact, so as to ensure stable pond water level and prevent river crabs from escaping from seepage leaks and the inlet and outlet. Especially for newly dug crab ponds, even more attention should be paid to preventing crab escape.

4. Maintain a quiet environment in the pond. River crabs require a relatively quiet environment. Artificial disturbance and invasion by enemies often cause river crabs to die during molting. Therefore, in the process of pond crab farming, the crab pond environment must be kept quiet, and the river crabs' feeding and molting process should not be disturbed too much. Especially during the period when river crabs molt in large numbers, the movements of feeding bait and cleaning the feeding ground should be gentler, so as to improve the survival rate of molting.

5. Strengthen the prevention and control of enemies. If rats, snakes and the like are found, spear and catch them promptly, and promptly eliminate rats with medicated bait.

6. Do a good job in anti-theft work. In autumn, sexually mature adult crabs come ashore in large numbers. Especially at night, river crabs come ashore and crawl along the anti-escape boards, making them very easy to catch. Therefore, specially assigned personnel should be arranged at night for all-night duty to avoid man-made losses.