Key Technical Points for Two-Crop-Per-Year Freshwater Shrimp (Macrobrachium nipponense) Culture in a Single Pond
Two-crop freshwater shrimp culture is a production technique that, based on the growth pattern of freshwater shrimp, makes full use of water surface resources to raise two crops of freshwater shrimp per year. The first crop of freshwater shrimp reaches an average yield of 40 kg per 0.067 hectares, and the second crop averages over 50 kg per unit, thereby achieving relatively high economic returns.
(1) Pond preparation: The pond area is 0.33--0.8 hectares, with a water depth of 1.0--1.2 m. Sandy soil or loam is acceptable. The slope ratio is 1:2--1:3. The pond must not seep water, and the bottom silt should be controlled at around 30 cm. The inlet and outlet systems should be complete, with escape-prevention mesh installed at the inlet and outlet, and attachment structures set up to provide hiding and resting places for the freshwater shrimp, which can also increase the shrimp-carrying capacity of the pond. Generally, artificial attachments such as tea tree branches and pine branches are used; water plants can also be planted in the early stage, and tea tree branches, pine branches, etc. used in combination during the mid-to-late stage.
(2) Supporting equipment: Generally, about 1 water pump is provided per 1.33 hectares of pond. For high-yield intensive culture ponds, 1 aerator and 1 water pump are provided per 0.67 hectares. Generally, each household is equipped with 1 self-made pellet feed machine.
(3) Stocking
(1) First crop freshwater shrimp culture: Stocking time is January--February, mainly stocking juvenile shrimp that have overwintered in ponds, with a size of 500--1,000 individuals/kg, and an average stocking density of about 1 kg per 0.067 hectares.
(2) Second crop freshwater shrimp culture: Stocking time is June--July, mainly stocking shrimp fry bred in the same year, with a size of 1.5--2.0 cm per individual, and an average stocking density of 30,000 fry per 0.067 hectares, while mixed stocking 500 summer fingerlings of silver carp and bighead carp.
(4) Feeding and management
(1) Feeding: The type of feed can be selected according to local conditions. Rapeseed cake, soybean cake, special feed for freshwater shrimp, self-made pellet feed, snail and mussel meat, trash fish, etc. can all be used. Generally, concentrated feed is the main component, supplemented by animal-based feed. The daily feeding amount is usually controlled at 3%--10% of the shrimp body weight. Generally, feed 2 times a day: at 7--8 a.m., feed 1/3 of the daily amount; at 5--6 p.m., feed 2/3. When feeding, use the method of scattered broadcasting, mainly spreading around the pond periphery and on the attachments so that the freshwater shrimp can feed evenly.
(2) Fertilization: During the culture process, always maintain the water quality as “fertile, lively, tender, and refreshing” to ensure good water quality in the shrimp pond and sufficient natural feed. In the early stage of culture, use the direct fertilization method; depending on water quality conditions, apply 50--100 kg of organic fertilizer per 0.067 hectares each week. In the mid-to-late stage of culture, switch to organic fertilizer that has been rotted and fermented; depending on water quality conditions, apply 100--200 kg per 0.067 hectares every half month (with water).
(3) Water quality management: In the early stage of culture (March--May), control the transparency at 20--25 cm; in the middle stage of culture (June--July), control the transparency at around 25 cm; in the late stage of culture (August--October), control the transparency at around 30 cm. If the culture conditions are relatively good, with power support reaching over 0.3 kW per 0.067 hectares, then the transparency can be kept at 10--20 cm throughout the culture process. The spread of aquatic plants must be controlled; in particular, floating-leaf plants and free-floating plants must be completely removed, and floating plants must be strictly controlled. Water exchange should follow the principle of “small inflow, small outflow” to prevent nutrient loss.
(5) Harvesting and marketing: For first crop freshwater shrimp culture, rotational harvesting generally begins at the end of April, with concentrated harvesting by the end of June. For second crop freshwater shrimp culture, rotational harvesting generally begins in October, with concentrated harvesting around the Spring Festival.