Detailed Explanation of Key Points for Freshwater Shrimp Breeding Technology in Crab Ponds

The freshwater shrimp, scientifically named Macrobrachium nipponense, is also known as the Oriental river prawn. The artificial breeding technology for freshwater shrimp fry is as follows:

1. Selection and keeping of parent shrimp. Parent shrimp selected for artificial breeding are required to have a standard body shape, pure body color, be plump and healthy, free from disease and injury, and have well-developed gonads. Female shrimp should have a body length of over 6 cm, and male shrimp should be somewhat larger. They can be selected from large shrimp caught in the wild or from artificially cultured ponds. The selected parent shrimp must be kept in a dedicated pond. The parent shrimp pond should have an area of 1-3 mu and a water depth of about 1 m. Before stocking the parent shrimp, strict pond cleaning and disinfection must be carried out, and the water inlet must be sealed and blocked with fine-mesh netting to prevent wild fish and other predators from entering. Generally, 1 mu of water surface can hold 5-10 kg of parent shrimp. After the parent shrimp are introduced into the pond, feeding management should be strengthened. Feed concentrated feed once every 2 days so that the freshwater shrimp accumulate a large amount of nutrients, promote gonadal development, advance egg laying, and lay a solid foundation for the smooth progress of artificial breeding.

2. Spawning and hatching. Freshwater shrimp spawning and hatching can be carried out in net cages (nursing cages), and the shrimp fry are also cultured in the same net cage. The net cage material can be polyethylene net cloth with a mesh size of 196 meshes/cm2, sewn into a net cage, with one polyethylene rope of 3X15 specifications mounted inside both the bottom and the upper opening of the cage. The cage is rectangular, with specifications of 10 m X 6.67 m X 1.7 m. It is installed as an open floating type, so that the net cage has 0.3 m exposed above the water surface as an anti-escape net. Place 2-3 sq m of aquatic plants in the cage, and place 1-2 small wooden-frame net cages for hatching. The hatching cage specifications are 1.7 m X 1 m X 0.5 m, with a mesh size of 12 meshes/cm2. A brick is tied to each of the four corners of the hatching cage respectively, so that the cage is exposed about 5 cm above the water surface. In early March, start feeding the overwintering parent shrimp. The amount of feeding increases as the water temperature gradually rises. In early April, the daily feeding amount can be increased to 4%-5% of the weight of the parent shrimp. Let the freshwater shrimp fatten, mate, and spawn in the overwintering pond (cage). For ovigerous female shrimp used for net cage breeding, the eggs are required to begin showing compound eyes. Place 700-1000 ovigerous female shrimp per net cage. After 6-7 days of hatching in the hatching cage, the larvae can break the membrane and detach from the parent. At this time, the hatching cage together with the post-hatching female shrimp can be taken out of the nursing cage.

Spawning and hatching can also be carried out in a spawning pond. The area of the spawning pond should preferably be 1-3 mu, with a water depth of about 1 m. The pond slopes should be free of weeds, the ventilation conditions should be good, the pond bottom should be flat, drainage should be convenient, and the work of pond cleaning and drug disinfection should be done in advance.

3. Net cage shrimp fry rearing. Feeding should begin on the day the larvae are moved from the hatching cage into the nursing cage, using 0.5-1 kg of soybeans per day. After soaking in water, grind into a slurry, remove the bean residue, and feed once in the morning and once in the afternoon, sprinkling it into the nursing cage. When the young shrimp grow to about 2 cm, while sprinkling soybean milk, a small amount of fine wheat flour or bran should also be added. The water quality in the cage should be fertile and clear, and the transparency can be controlled at 25-35 cm. After 25 days of rearing, the young shrimp can reach the stocking size.

4. Shrimp fry rearing in cement ponds and earthen ponds. Rearing shrimp fry in cement ponds uses indoor overwintering cement ponds for tilapia as hatching ponds for freshwater shrimp. The water source should preferably be fresh, unpolluted river water. The pond water depth is 80-100 cm, and the water temperature is above 20°C. Put the parent shrimp retained from the previous year (shrimp that have already spawned) centrally into net cages (100 cm x 50 cm x 50 cm) in the hatching pond, with a stocking density of 300-400 shrimp/cage. Feed a small amount of soybean cake on time every day, and add water and discharge waste once each. At a water temperature of 20-26°C, shrimp fry can be hatched after 6-7 days.

Rearing shrimp fry in earthen ponds is carried out in outdoor earthen ponds. In the morning when the light is good, use an 80-mesh net cage to scoop out the larvae and move them to the outdoor earthen pond. The stocking density is 400,000-600,000 larvae/mu. If natural food is insufficient after the larvae are put into the pond, in addition to promptly cultivating good water quality, a portion of fine soybean milk must also be fed every day. After more than 1 month of rearing, when the body length reaches 1.5-2 cm, they can be caught and divided among ponds for adult shrimp culture.

For mixed culture of freshwater shrimp and river crab, river crab and Oriental river prawn fry can be stocked in March each year, with 550-600 Yangtze River crab juveniles per mu (specifications of 150-200 crabs/kg) and about 18 kg of Oriental river prawn fry (specifications of 1600-1800 shrimp/kg). During the spring growing period of small-sized river crabs, the main focus is on freshwater shrimp culture, ensuring that more than 35 kg of commercial shrimp per mu can be harvested in June, while river crabs also have sufficient water body space and their growth is not affected.