Crayfish, also known as red shrimp or crawfish, belong to the genus *Procambarus* and are native to the United States. These crustaceans are a vital species in freshwater aquaculture and have been introduced to various regions around the world, including China, where they have become an important resource in inland water farming. Originally brought into China from Japan during World War II, crayfish populations have since expanded significantly, especially in the middle and lower reaches of the Yangtze River.
In 2006, Anji County in Zhejiang Province saw substantial growth in crawfish farming, with 432 mu (about 29 acres) dedicated to breeding *Procambarus clarkii*. A trial project was conducted in 12-acre ponds in Qushan Township, focusing on the cultivation and management of this species. The following details summarize the methods and results of the experiment:
**Materials and Methods**
1. **Pond Conditions**: Five test ponds, each between 2 to 3 acres, totaling 12 acres, were used. Water depth was maintained at about 1 meter, with clean, fresh water supply. Some areas resembled swamps, with varying shades of vegetation covering approximately one-quarter of the pond area. The walls were constructed using cement bricks or boards to prevent escape, and artificial shelters such as bamboo tubes, tiles, and plastic pipes were placed inside.
2. **Preparation Before Stocking**:
- Ponds were drained and dried for a month before stocking, then treated with lime slurry at 100 grams per acre for 10 days.
- After filling the ponds to 50 cm, fermented organic manure was applied at 300 kg per mu to cultivate natural food organisms.
- Aquatic plants like *Vallisneria*, *Hydrilla verticillata*, *Eichhornia crassipes*, and terrestrial grasses were planted, covering no more than two-thirds of the pond area.
- Snails were introduced at 200–300 kg per acre as a supplementary animal feed.
3. **Stocking Shrimp**: Between mid-March and mid-June, 1050 kg of seedlings were stocked across the 12-acre ponds. Care was taken during transportation to avoid dehydration and physical damage.
4. **Feeding Strategy**:
- During the early stages, crawfish were fed insect larvae, cladocerans, copepods, and powdered feeds like barley and wheat bran.
- In May, the diet shifted to wheat bran, bean cake, and green vegetables like pumpkin and melon skins.
- From August to September, more animal-based feeds such as fish, earthworms, and waste were introduced, along with dehulling agents to support molting.
5. **Daily Management**:
- Feed included vitamins and immune boosters, while excess vegetation was removed in summer to maintain water quality.
- Water quality was closely monitored, with dissolved oxygen levels kept above 5 mg/L, pH between 7–8.5, and transparency at 35 cm. Regular water changes and microbial treatments were performed.
- Shelling periods were managed carefully, with high-quality feed provided immediately after molting.
- Disease prevention measures included disinfection, regular lime and bacterial applications, and removal of harmful organisms.
6. **Harvesting**: Shrimp were harvested after 1–2 months of feeding, when they reached over 30 grams. Methods included traps, nets, and drying pools.
7. **Breeding**: Farmers retained 200 kg of adult shrimp for breeding, leading to successful reproduction and the growth of young crawfish up to 1.5 cm.
**Test Results**
- Total harvest from June to December amounted to 2,520 kg, generating 60,480 yuan in revenue. Additional 1,000 kg brought in 60,000 yuan, totaling 120,480 yuan.
- Total costs, including infrastructure, seeds, feed, and labor, were 56,400 yuan, resulting in a net profit of 64,080 yuan.
**Discussion and Summary**
- The market demand for *Procambarus clarkii* is rising, with wholesale prices reaching up to 30 yuan/kg. With government support for freshwater aquaculture, crawfish farming has become a profitable and manageable venture.
- Proper planting of aquatic vegetation and snail introduction improves habitat conditions and provides natural food sources.
- Timely harvesting of larger individuals helps reduce pond density and promote faster growth.
- Selecting females for breeding is crucial, as males can store sperm for up to eight months, ensuring successful fertilization.
- Fresh, properly prepared feed is essential to prevent disease and ensure healthy growth.
This comprehensive approach highlights the potential of crawfish farming as a sustainable and economically viable practice in freshwater environments.
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