Mixed polyculture of ricefield eels, loaches, silver carp, bighead carp and lotus in the same pond yields fast growth
In recent years, specialized farming households in Liaozhong County, Liaoning Province, have broken with traditional farming methods, reformed their cropping and farming systems, and adopted a multi-component composite three-dimensional development approach. Based on ecological principles, farmers adopted ecological lotus intercropping and supplementary polyculture, raising income from lotus ponds by 2 to 3 times.
I. Pond construction
Choose ponds with abundant water sources, smooth intake and drainage, unpolluted water quality, fertile soil, flat terrain and strong water retention. For natural ponds, an area of 10 mu to 20 mu, a depth of 1 m to 1.5 m, and a bottom mud thickness of 20 cm to 40 cm are suitable. In winter, mix a certain amount of plant straw and pig, cattle and chicken manure into the mud; build pond embankments more than 70 cm high to prevent pond water from overflowing and fry from escaping when rainstorms come; where conditions permit, build a 50 cm to 70 cm anti-escape wall around the pond with bricks and cement, cap the top of the wall with cross-laid bricks in a “T” shape to prevent ricefield eels from hooking their tails on the wall and escaping; coat both the inner and outer sides of the wall with a layer of cement slurry to plug leaks, and install stainless steel fine-mesh blocking nets at the water inlet and outlet. Keep the water depth at a minimum of 15 cm to facilitate feeding and respiration by the eels and loaches. When planting lotus seed stock in spring, reduce the amount of lotus seed stock accordingly to prevent too many lotus leaves from blocking sunlight, while a moderate amount of lotus leaves helps cool the pond and avoid summer heat. Generally, use 200 kg to 300 kg of lotus seed stock per mu.
II. Stocking of fry and seed stock
Select eel seed stock that is strong, disease-free, uninjured, uniform in size, yellow on the dorsal side of the body, and with dark brown spots for stocking, at a size of about 30 individuals per kg, stocking 3000 to 5000 individuals per mu. Loach fry should be 0.5 g in size, as uniform as possible, stocked at 6000 to 10000 individuals per mu. Appropriately add silver carp and bighead carp, at a size of 10 to 15 individuals per kg, stocking 500 to 700 individuals per mu. Around June, stock silver carp and bighead carp summer fry at 700 to 2000 individuals per mu as live bait for ricefield eels and loaches, but do not stock black carp or common carp. Where lotus is intercropped, grass carp may be stocked, using the practice of “feeding grass with duckweed”; fresh duckweed and grass feed must be fed every day, and grass carp feed must not be interrupted or underfed, so as to prevent grass carp from switching to eating lotus leaves and causing losses.
III. Feed feeding
Ricefield eels mainly eat animal feed, such as earthworms, fly maggots, small fish, shrimp, yellow mealworms or pig and poultry offal; plant-based bait is supplementary, such as soybean cake pieces, wheat bran, duckweed, tofu workshop scraps, or compound feed. The feed must be fresh; spoiled feed must not be fed. For newly stocked eel fry, first feed small animal bait, and after domestication, feed compound feed. In lotus ponds, it is best to stock eel fry first, and after they adapt to compound feed, then stock loach fry. If eel and loach fry are stocked at the same time, it will certainly affect the domestication of the eels. Loaches mainly eat plant-based feed, such as aquatic plants, vegetable leaves, rice bran and soybean cake, supplemented with animal bait and compound feed, with a feeding amount of 5% of body weight. For silver carp and bighead carp, regularly splash fermented manure water into the lotus pond to cultivate plankton as bait, splashing 50 kg to 100 kg of manure water per mu each time, while also providing high-quality plankton bait for the loaches.
IV. Disease prevention and control
Implementing ecological intercropping of eels, loaches, silver carp, bighead carp and lotus helps adjust the multi-component composite farming structure, improve the water environment, and achieve good ecological disease prevention results. However, artificial disease prevention work must also be done well. Before stocking fry and seed stock, soak them for 5 minutes in a 1‰ potassium permanganate solution or a 3% to 5% salt solution to kill parasites. Pay attention to preventing and treating common diseases of eels and loaches, such as putrefactive skin disease, saprolegniasis, tail rot and capillary nematode disease, and also promptly eliminate biological enemies such as water rats.
V. Daily management
Pay attention to controlling the water level; the water depth should preferably be kept at 15 cm to 30 cm. During the summer flood season, always watch for rising water levels to prevent fish from escaping. During the high-temperature season from July to August, promptly change the water or add fresh water.
VI. Timely harvesting
Silver carp and bighead carp can be harvested from “Autumn Equinox” to “Winter Solstice”, generally yielding 250 kg to 300 kg of silver carp and bighead carp per mu. From September, tools such as eel cages can be used to catch eels and loaches; for harvesting before overwintering, both hands can be used to turn over the mud block by block and take them out. If they are to be kept for sale around the Spring Festival, freeze prevention work must be done well during the overwintering period, and if necessary, drain the water and cover them for freeze protection. If overwintering with water, the water layer must not be too shallow, to prevent freezing. After ricefield eels are stocked as seed stock, they can grow to 30 cm to 40 cm after 3 months of rearing. Generally, about 200 kg of eels and loaches are caught per mu, and the average lotus yield per mu is 2000 kg to 3000 kg. The total annual income from lotus and supplementary polyculture fish averages 5000 yuan to 8000 yuan per mu, 30% to 50% higher than single cropping and single-species farming.