Astragalus membranaceus, commonly known as "jaundice," is a carnivorous fish with the tendency to cannibalize when food is scarce. This behavior necessitates careful management in high-density farming systems. To optimize cultivation, small-scale pond culture—also referred to as "small pond dense culture"—is widely used. This method involves using cement ponds, earthen ponds, or net cages, each with an area of 30 square meters or less. Over many years, this system has proven effective, offering advantages such as ease of management, high survival rates, rapid growth, and significant economic returns per unit area. Below are the key technologies involved in implementing this system.
First, the design and construction of small ponds vary depending on local conditions. Cage culture is ideal for reservoirs or fish ponds, while paddy fields with good water retention can be converted into earthen ponds. If the paddy fields have poor water conditions, concrete pools are recommended. Cages are typically made from durable polyethylene mesh cloth, costing about 6-10 yuan per square meter and lasting up to three years. They should be rectangular, with a bottom area between 6-30 square meters and a depth of 1-1.5 meters. For shallow ponds, they can be fixed directly to the bottom, while deepwater areas may use floating cages made from waste oil barrels and tires.
Earthen ponds are cost-effective, especially for converting rice paddies. A 1-mu (approximately 667 square meters) paddy field conversion costs around 3,000 yuan. Each pond should have at least 50 cm of water depth and drainage ditches between rows. The pond perimeter is enclosed with polyethylene netting, buried 20-30 cm underground, to prevent escape by yellow locusts.
Concrete ponds, though more expensive (30-50 yuan per square meter), offer long-term durability and efficient water management. Their size is usually 10-30 square meters, with a depth of 60-80 cm. The pool edges are curved to prevent escape, and the bottom slopes slightly toward the outlet. Overflow pipes are installed to control water levels, and plastic baskets are placed near the outlets to prevent fish from entering.
Next, preparation before stocking includes demineralizing new cement ponds by soaking them in water for over seven days. Mesh cages should be soaked in water to allow algae to grow, preventing injury to the fish. Aquatic plants like water hyacinth are then laid in the ponds, ensuring no gaps and keeping plants at least 40 cm away from the walls. Disinfection with products like "Cangbao No. 2" or lime is essential, followed by treatment to kill parasites.
For seed selection, wild Astragalus is commonly acquired from April to September and sold before winter or Spring Festival. Healthy specimens are chosen based on appearance, avoiding those with signs of disease or trauma. After purchase, they are immediately introduced into the pond with aquatic plants and fed appropriately. Feeding methods include chopped quail, pork liver, and fish, with added vitamins and medications to enhance growth and immunity.
Daily management involves monitoring feeding behavior, gradually increasing feed amounts, and removing leftovers. Fish showing abnormal behavior should be removed promptly. During hot weather, shade nets are used to lower water temperature, and water depth is increased to maintain optimal conditions.
Finally, harvesting depends on the type of pond. In cement tanks and cages, fish can be easily captured by moving through the aquatic plants. For earthen ponds, grass is stacked, and fish are collected using large nets. This method works best during the active season, and fish must be harvested before dormancy if selling in winter.
Overall, small pond dense culture offers a practical, efficient, and profitable way to raise Astragalus membranaceus, combining traditional practices with modern techniques for sustainable aquaculture.
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