Detailed Explanation of Key Points in Macrobrachium rosenbergii Farming Management Techniques

   Macrobrachium rosenbergii, also known as the Malaysian prawn, is a large long-armed freshwater prawn native to the Indo-Pacific region. It breeds in seawater and lives in various types of freshwater or brackish water. It has characteristics such as a wide feeding range, fast growth, large individual size, delicious meat and rich nutrition. It was introduced to China from Japan in 1976, and the farming scale has continued to expand. Our city began farming it in 1995. At present, the farming area has reached more than 200 mu, with an average yield of 100 kg per mu and an average profit of more than 1500 yuan per mu, making the benefits very considerable. The farming techniques for Macrobrachium rosenbergii are introduced as follows:

    I. Biological characteristics:

    1. Morphological structure: The body of Macrobrachium rosenbergii is cylindrical. The cephalothorax is noticeably thicker and larger than that of Chinese white shrimp, and the abdomen is shorter. It has 5 pairs of walking legs in total and poor swimming ability. Its body color is light bluish yellow, with brownish yellow stripes interspersed. The second walking legs of male prawns are very well developed, with a length 3 times the body length, a relatively large head, and an abdomen narrower than that of female prawns. The head and second walking legs of female prawns are smaller than those of male prawns. Macrobrachium rosenbergii is dioecious.

    2. Living habits and feeding habits: Macrobrachium rosenbergii is an aquatic benthic organism. It does not like strong light and is attracted to weak light. It hides by day and comes out at night. During the day, it mostly hides in depressions at the bottom of the pond and under shelter, with little activity, but it will also eat when feed is given. At night, it is frequently active and searches for food everywhere. Macrobrachium rosenbergii is an omnivorous animal, and the required food composition differs at different growth and development stages. Under artificial farming conditions, compound feed, trash fish and shrimp, and oilseed meals can be fed.

    3. Ecological habits

    Macrobrachium rosenbergii is a tropical shrimp species and requires relatively high water temperature. The suitable temperature range is 18—34 degrees Celsius, and the optimum water temperature is 28—31 degrees Celsius. The minimum critical temperature is 14 degrees Celsius, and the maximum critical temperature is 35 degrees Celsius. Macrobrachium rosenbergii is not tolerant of low oxygen. When dissolved oxygen is above 5 mg/L, growth is best; below 3 mg/L, the shrimp will surface for air. Macrobrachium rosenbergii is a euryhaline shrimp species, with an adaptation range of 10‰—30‰, and the best growth salinity is below 10‰; the suffocation salinity is 33‰, and the required pH value is between 7—8.5.

    II. Preparation before stocking

    1. Selection of shrimp ponds

    Adult shrimp ponds should be built in places with good ecology, a beautiful environment, sufficient water sources, convenient drainage and irrigation, fresh and pollution-free water quality, no drying up in drought, no flooding in waterlogging, and sunny and ventilated conditions. The pond bottom is preferably semi-muddy, with convenient transportation and power supply. Shrimp ponds can be excavated in barren low-lying land, or ponds and river ditches previously used for fish farming can be used for farming. Coastal and lakeside brackish water and shrimp ponds with salinity below 15‰ can also be used for farming.

    2. Pond area

    Intensive or main farming ponds are generally 1—3 mu. If the pond area is too large, Macrobrachium rosenbergii tends to concentrate along the pond edges and cannot fully use the water body space. If a new pond is dug, an east-west orientation is preferable, with a length-to-width ratio of 4:1 or 3:1. This is convenient for operation, and the larger sunlit area is beneficial to shrimp growth.

    3. Pond water depth

    According to the living habits of Macrobrachium rosenbergii, the water depth of intensive ponds is 0.7—1 m, and the maximum depth of intensive ponds should not exceed 1.5 m. In this way, the light-transmitting layer is larger, which helps increase water temperature, enhance photosynthesis of phytoplankton, and increase dissolved oxygen in the water. At the same time, exposure of the shrimp body to sunlight also facilitates calcium absorption and promotes shell growth.

    4. Pond clearing and disinfection

⟧NL⟧    For disinfection of shrimp ponds, quicklime is generally used. There are two disinfection methods: dry method and with-water method. Dry disinfection is carried out within 15—20 days before stocking shrimp fry, that is, in early May, and can be carried out at noon on a sunny day. The pond water should first be drained, leaving about 10 cm of water at the bottom of the pond. Use 100—150 kg of quicklime per mu. For with-water disinfection, use 250 g of quicklime per cubic meter of water. Newly dug ponds should also be disinfected, using 75—100 kg of quicklime per mu, to increase the calcium content of the pond. For ponds after disinfection, generally 5—8 days before stocking shrimp fry, add water to 70—100 cm, and install a filter screen at the water inlet to prevent wild trash fish and other enemies from mixing in.

    5. Applying base fertilizer to cultivate water quality

    Especially for newly dug shrimp ponds, the pond bottom is poor in substrate and the water quality is lean, so sufficient base fertilizer should be applied. Before the shrimp fry are put into the pond, cultivate abundant natural feed so that the shrimp fry have enough feed after being put into the pond. Chemical fertilizers or special powerful ecological fertilizers can be applied.

    6. Setting up shelters