In 2001, we initiated the "External Swing Mesh Eco-Fish Rafting" project to explore and implement ecological farming techniques, particularly focusing on turtle fishing nets. Following two years of breeding experiments, the project yielded significant economic and social benefits.
**1. Materials and Methods**
**1.1 Selection of Aquaculture Waters**
Based on the natural behaviors of soft-shelled turtles—such as their aversion to squid, wind, and dirty water—we selected test sites at the Shengze, Pingwang, Zhenze, and Meiyu branches. These lakes are located in the Taihu Basin hinterland, featuring clean, unpolluted fresh water with high dissolved oxygen levels, good lighting, abundant benthic organisms, and a smooth water flow. The water depth remains stable between 2.5 to 3.5 meters, with a flat bottom ideal for aquaculture.
**1.2 Mesh Design and Installation**
The net enclosure system includes wall nets, gabions, support poles, and anti-escape mechanisms. The wall net, made of 3mm polyethylene, is fixed to the poles using ropes and pillows as supports. The net is leveled vertically and secured at the bottom with gabions pressed into the mud. The top of the net extends 1–1.5 meters above the water surface. Crab cages were used to monitor for escapes. Platforms were installed every 3–5 meters, each about 2–3 square meters, serving as feeding and drying areas.
**1.3 Seed Stocking**
Healthy, disease-free, and non-invasive turtle seedlings were selected from greenhouses. Stocking was done when the water temperature reached around 25°C. In 2001, 10,500 turtles (average weight: 200g) were stocked at a density of 100 per mu. In 2002, 61,800 turtles (average weight: 150g) were stocked at 60 per mu. A small number of older fish were also raised to enhance biodiversity.
**1.4 Daily Management**
**1.4.1 Feeding**
Live snails were introduced into the lakes before stocking to serve as natural bait. After one week, liver-based feed was used to encourage turtle feeding, followed by animal-based feeds like small fish and quail meat. All food was placed on platforms exposed to the water surface.
**1.4.2 Monitoring**
Regular checks were conducted to observe turtle behavior and ensure the integrity of the mesh and gabions. Preventive measures were taken against rat damage.
**1.5 Disease Prevention**
Seedlings were disinfected with a 5% salt solution or 20mg/L potassium permanganate for 10 minutes. During the high-temperature disease season, lime solution (25mg/L) was applied to control pathogens, and calcium was added to balance pH.
**2. Test Results**
**2.1 Harvesting**
Harvests began in late September when water temperatures dropped, reducing turtle activity. Crab cages and gill nets were used. In 2001, 6,930 turtles weighing 3,089 kg were harvested, averaging 440g each with a 66% catch rate. In 2002, 40,540 turtles weighing 16,643 kg were harvested, averaging 410g with a 65.6% rate. Both exceeded the target of 400g per turtle and 60% survival rate.
**2.2 Economic Benefits**
In 2001, total input cost was 175,305 yuan, output was 214,880 yuan, yielding a net profit of 39,575 yuan, or 377 yuan per mu. In 2002, input was 884,955 yuan, output 1,289,892 yuan, with a net profit of 394,937 yuan, or 383.4 yuan per mu. The input-output ratio improved from 1:1.22 in 2001 to 1:1.44 in 2002.
**3. Discussion**
(1) The external swing mesh method mimics natural conditions, offering low costs and high economic returns. At 60 yuan per kilogram, the net profit per mu exceeds 370 yuan, with better results at lower stocking densities. However, optimal stocking size and density require further study.
(2) Turtles raised in this system grew faster than those in traditional methods—1.2 times in 2001 and 1.73 times in 2002. Over 80% met market standards, with a survival rate far exceeding 60%, proving the technique's feasibility.
(3) By simulating natural habitats and using more natural food sources, the turtles developed strong muscles, a sleek shell, and excellent taste. Although initial quality was affected by short culture periods, extending the growth cycle and introducing more natural prey could improve quality further.
(4) This ecological approach also allows for raising other aquatic species, promoting biodiversity and improving water quality. Polyculture stabilizes fish production and enhances market stability. With reduced chemical use and increased natural food availability, the turtles produced are cleaner, more nutritious, and more valuable in the market.
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