In 2001, we initiated the "External Swing Mesh Eco-Fish Rafting" project to explore sustainable turtle farming techniques within an ecological framework. Following two years of trials and experiments, we achieved significant economic and social benefits, proving the viability of this method.
**Materials and Methods**
**1.1 Selection of Aquaculture Waters**
Based on the natural behavior of soft-shelled turtles—such as their aversion to strong winds, dirty water, and squid—we selected test sites at the Shengze, Pingwang, Zhenze, and Meiyu branches. These locations are situated in the hinterland of the Taihu Basin, offering clean, unpolluted freshwater with high dissolved oxygen levels, ample benthic organisms, and a stable water flow. The permanent water depth ranges from 2.5 to 3.5 meters, with a flat bottom ideal for aquaculture.
**1.2 Mesh Design and Installation**
The net enclosure was constructed using wall nets, gabions, support poles, and anti-escape measures. The main structure was made of 3mm polyethylene mesh, sewn and secured to wooden posts using ropes. The bottom was anchored with gabions pressed into the mud. The net perimeter was kept 1–1.5 meters above the water surface, with crab traps placed around the edges to monitor for escapes. Platforms were installed every 3–5 meters, each covering about 2–3 square meters, serving as feeding and drying areas.
**1.3 Seed Stocking**
Healthy, disease-free turtle seedlings were sourced from greenhouses. Stocking was done when the water temperature reached above 25°C, ensuring a smooth transition from greenhouse to open water. In 2001, 10,500 turtles (200g per turtle) were stocked at a density of 100 per mu. In 2002, 61,800 turtles (150g per turtle) were stocked at 60 per mu, along with a small number of older fish for biodiversity.
**1.4 Daily Management**
Before stocking, live snails were introduced to the lakes to serve as natural bait. After stocking, the turtles were initially fed with liver, then gradually transitioned to animal-based feeds like small fish and quail meat. All feed was placed on the platforms, which remained exposed to the water surface for easy access.
Regular monitoring of turtle activity and feeding patterns was conducted, along with checks on the integrity of the netting and gabions to prevent damage from pests like rats.
**1.5 Disease Prevention**
Healthy seedlings were disinfected before being released, typically by soaking them in a 5% salt solution or a 20mg/L potassium permanganate solution for 10 minutes. During the hot season, lime solution was applied to the water to control pathogens, and calcium was added to maintain a balanced pH level.
**Test Results**
**2.1 Harvesting**
Harvesting began in late September when water temperatures dropped and turtle feeding decreased. Crab cages and gill nets were used for collection. In 2001, 6,930 turtles were harvested, totaling 3,089 kg, with an average weight of 440g and a catch rate of 66%. In 2002, 40,540 turtles were collected, totaling 16,643 kg, averaging 410g and achieving a 65.6% catch rate. Both results exceeded the target of 400g per turtle and a 60% survival rate.
**2.2 Economic Benefits**
In 2001, total input costs were 175,305 yuan, with output reaching 214,880 yuan, resulting in a net profit of 39,575 yuan, or 377 yuan per mu. In 2002, input costs rose to 884,955 yuan, but output increased to 1,289,892 yuan, yielding 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.
**Discussion**
This method mimics natural ecosystems, reduces costs, and delivers strong economic returns. At 60 yuan per kilogram, the profit per mu exceeded 370 yuan, showing clear financial advantages. Lower stocking densities and smaller sizes tend to reduce costs and increase profitability, though further research is needed to determine optimal stocking levels.
Turtles raised in the external mesh system grew faster than those in traditional enclosures. In 2001, growth was 1.2 times higher, and in 2002, it reached 1.73 times. Over 80% of turtles met market size requirements, with survival rates far exceeding 60%, confirming the technical feasibility of the method.
To preserve wild traits, we created a simulated eco-environment with natural bait. The resulting turtles had better physical characteristics, including a sleek shell, wide skirt, and strong muscles, leading to superior taste and nutrition compared to greenhouse-raised turtles. However, longer breeding periods and more diverse natural food sources could further enhance quality.
Finally, this method allows for polyculture with other aquatic species, improving water quality and resource utilization. By integrating soft-shelled turtles with other fish, we stabilized production and supported the local aquatic market. Using natural food and reducing chemical inputs not only lowered costs but also improved turtle quality. As a result, the turtles produced through this method are cleaner, more nutritious, and have greater market value.
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