Latest Achievements in Still-Water, Soil-Free Ecological Loach Farming

The soil-free loach farming aquaponics project is suitable for returning-home entrepreneurship, diversified operations, and developmental resettlement in reservoir areas. The project inventor, Mr. Zhou Wenzong, associate researcher at the Institute of Biotechnology, Nanjing University, director of the Ecological Environment Research Center of the Henan Academy of Sciences, and holder of dual doctorates in ecological engineering and aquatic biology in China's ecological farming field, has presided over the completion of 24 provincial-level research projects, participated in 11 projects including the “Tenth Five-Year Plan” National Major Science and Technology Special Project, the National Science and Technology Tackling Plan, the 863 Program, and provincial-level projects, and holds 7 national invention patents as the first inventor. After years of scientific research, following his invention of the still-water, soil-free ecological farming model for rice field eels and the realization of semi-artificial breeding of rice field eels in shallow water without soil, in recent years he has broken through traditional farming methods and pioneered four major scientific and technological innovation projects: “soil-free loach farming in impermeable membrane ponds,” “loach farming with soil in cement ponds,” “loach farming with biogas residue and biogas slurry,” and “co-cultivation of loach with aquatic vegetables and melons in the same pond.”
I. Current Status and Development Trends of Loach Farming
Loach is distributed in rivers, ditches, paddy fields, ponds, lakes, and reservoirs across China, and is most widely distributed in the middle and lower reaches of the Yangtze and Pearl River basins. Enjoying the reputation of “turtledove in the sky, loach on the ground” and “ginseng in the water,” loach is not only a nutritious and widely praised delicacy but also has relatively high medicinal value. In recent years, demand for loach in domestic and international markets has been considerable. Annual domestic market demand is 100,000 to 150,000 tons, while international markets are mainly Japan and South Korea, with annual demand of about 100,000-plus tons. However, China's current market supply is only 50,000 to 60,000 tons, leaving a large gap. The market situation of supply falling short of demand has driven loach prices up year after year. From 1995 to the present, loach prices have risen from 5 yuan/kg to 20-30 yuan/kg, and in the Jiangsu, Zhejiang, and Sichuan markets, the winter selling price of blue loach reaches as high as 50 yuan/kg.
The relatively large market space and profit space have led to the rapid development of the loach farming industry. The domestic loach farming area is 15 million to 20 million sq m (that is, 20,000 to 30,000 mu), requiring 15 million to 20 million kg of fry and fingerlings each year, with market sales of about 500 million yuan, mainly concentrated in Jiangsu, Henan, Hubei, Shandong, Anhui, and Sichuan provinces. The farmed variety is basically the large-scale loach (yellow-board loach). With the rapid development of the artificial loach farming industry, the contradiction of weak farming technology has gradually become prominent. At present, the factors restricting its development mainly include:
1. Limited sources of fry and fingerlings
Fry and fingerlings are the foundation of production. At present, fry and fingerlings are still mainly obtained by wild capture, and the proportion of artificially bred fry and fingerlings is extremely small. No large-scale artificial fry and fingerling breeding enterprise has yet been seen in China, and large-scale breeding farms in Anhui, Sichuan, Hubei, and other places are mainly based on fry rearing. The main reason is that the survival rate of loach fry with a body length of 7-20 mm (in the transition period from gill respiration to intestinal respiration) is extremely low, averaging less than 20%, which seriously restricts large-scale fry production. Rising loach market prices will inevitably cause a shortage of wild loach fry and fingerlings, forming a vicious cycle and increasing the cost of loach farming.
2. Low conversion efficiency of compound feed
At present, research on the nutritional requirements of loach is not sufficiently in-depth, and there is relatively little special compound feed for loach in China. Most products are sold as loach compound feed after other fish feed formulas have been slightly changed or not changed at all. Therefore, feed utilization is extremely low, and the feed conversion ratio is generally between 4.0 and 6.0, with some even as high as 10.0, seriously restricting the healthy development of the loach farming industry.
3. Single farming model
Domestic loach farming is concentrated in Jiangsu, Henan, Hubei, Anhui, and other provinces, and is basically a pond net-enclosure farming model. The vast majority of farmed varieties are yellow-board loach, and there are no successful cases of cage farming, soil-free farming, or blue loach farming.
4. Low degree of intensive farming
Because artificial loach farming is still in its initial stage and mainly consists of scattered single-household, single-pond holding models, the farming level is relatively low and mostly experience-based. Many new farming technologies cannot be effectively promoted, pests and diseases cannot be effectively prevented and controlled, and industrial farming and four-season farming are still uncommon.
5. Serious water body pollution
Due to high loach farming density, large food intake, and abundant residual bait and excrement, the farming water body is highly prone to eutrophication. The lower water layer is poor in oxygen, while sulfide, organic matter, and nutrients in the surface water layer increase, residual drugs accumulate, harmful microorganisms and pollution-feeding organisms dominate, the ecology of the farming water area becomes imbalanced, and various diseases occur frequently, especially in the middle and late stages of farming, causing serious pollution to groundwater and surrounding water bodies.

II. Development Trends of Loach Farming
With the development of science and technology and the expansion of farming scale, loach farming will show the following development trends:
1. Farming ponds tend toward miniaturization and intensification (about 400-500 sq m is best). A smaller feeding space is beneficial for loach feeding, reduces physical energy consumption, and makes water quality easier to regulate, thereby increasing yield per unit area;
2. Soil-free farming, industrial farming, or recirculating water farming are the development directions. Soil-free farmed loach has no fishy smell, good quality, water quality that is easy to regulate, fast growth, and a high survival rate; loach has strong vitality, tolerates low oxygen, requires a shallow-water environment, and is very suitable for industrial farming or recirculating water farming;
3. Cage farming has promising prospects. China is rich in small water bodies such as ponds and pits. Cage loach farming is easy to manage, convenient to harvest, and high-yielding, with promising development prospects;
4. Improve the loach-vegetable symbiotic system. Loach likes darkness and fears light, can eat insects, and is highly active. Its farming water body has a high degree of nutrient enrichment and high ammonia nitrogen content, making it suitable for planting aquatic vegetables on the water surface. This can purify water quality, reduce pest and disease damage, promote loach growth, and improve economic benefits. It is a very good aquaponics system;
5. Hybrid breeding and monosex seedling breeding are the focus of loach seedling breeding. At present, the main factor restricting the efficiency of loach farming is the slow growth rate of loach, with annual growth rarely reaching 3 times. The main reason is that the slow growth rate of male loach affects yield improvement. The growth rate of female loach is 80%-100% faster than that of males, and feminized seedling breeding will become a research hotspot. Yellow-board loach has the advantages of fast growth, strong stress resistance, and greater tolerance to low oxygen, but its flesh is loose and its taste cannot compare with blue loach. Blue loach, however, does not tolerate long-distance transportation, grows slowly, and is prone to disease. Using the two as parents for hybrid breeding is an inevitable trend;
6. Deep processing urgently needs strengthening. Loach deep processing has huge potential and an extremely broad market in fields such as health care, beauty, food, and medicine, which is conducive to extending shelf time on the market and increasing added value.
The patented and proprietary technologies pioneered by Dr. Zhou Wenzong - “soil-free loach farming in impermeable membrane ponds,” “loach farming with soil in cement ponds,” “loach farming with biogas residue and biogas slurry,” and “co-cultivation of loach with aquatic vegetables and melons in the same pond” - were developed through scientific research and achieved industrial production precisely in response to the above development trends.