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Crayfish, also known as freshwater crayfish, are native to the United States and have become an important species in freshwater aquaculture. These crustaceans are closely related to lobsters and shrimp. During World War II, they were introduced to Japan, where they gradually expanded their population and habitat. Today, they are a valuable resource in China's freshwater shrimp industry. In 2006, Anji County in Zhejiang Province saw significant success with Procambarus clarkii farming, covering 432 mu and generating substantial economic returns. The following is a summary of the trial aquaculture and breeding project conducted in a 12-mu pond in Jishan Township.
**First, Materials and Methods**
1. **Pond Conditions:** There were five test ponds, each ranging from 2 to 3 acres, totaling 12 acres. The water depth was maintained at about one meter. The ponds had a steady supply of clean, unpolluted water and were easily accessible. Some areas resembled swamps with varying shades of water, making up approximately 1/4 of the total pond area. The walls were constructed using cement bricks or boards to prevent escape, with more than three meters of flat space inside. Artificial shelters such as bamboo tubes, tiles, and plastic pipes were installed in the ponds.
2. **Preparation Before Stocking:**
- **Clearing the Ponds:** One month before stocking, the ponds were drained and dried. Lime slurry (100 grams per acre) was applied for about 10 days before introducing seedlings.
- **Water Filling and Fertilization:** After filling the pond with 50 cm of water, fermented organic manure was added at a rate of 300 kg per mu to cultivate natural food sources.
- **Planting Aquatic Vegetation:** "How much shrimp, see plants." Crayfish feed on aquatic plants like Vallisneria, Eichhornia crassipes, Water Lilies, and terrestrial grasses. The planting area should not exceed 2/3 of the total pond area.
- **Snail Introduction:** Snails serve as an additional animal feed source. They were introduced at a rate of 200–300 kg per acre and supplemented as needed.
3. **Stocking Shrimp:** Between mid-March and mid-June, 1050 kg of seedlings were placed into the 12-acre ponds. Care was taken during transportation to avoid dehydration and physical damage.
4. **Feeding Practices:**
- **Feed Composition:** Depending on the growth stage, different feeds were used. Seedlings were fed insects, cladocera, and copepods, while mature crayfish required wheat bran, bean cake, and animal-based feeds. During the overwintering period, more protein-rich diets were necessary.
- **Feeding Schedule:** Feedings occurred twice daily—once in the morning and once in the evening. The amount varied based on water temperature, weather, and feeding activity. Animal feed accounted for 8–12% of body weight, while dry feed was 3–5%.
5. **Daily Management:**
- **Feeding Management:** Vitamins and immune boosters were added to the feed. Animal waste was cooked before being fed. Extra grass was added if water levels dropped.
- **Water Quality Control:** Dissolved oxygen levels were kept above 5 mg/l, pH between 7–8.5, and water transparency around 35 cm. Water was changed every 15–20 days, and lime and photosynthetic bacteria were regularly added.
- **Shelling Management:** Feeding and water changes helped promote molting. High-quality feed was provided immediately after molting to avoid cannibalism.
- **Top Dressing:** Organic manure was applied every half a month at 15–20 kg per mu to maintain water fertility.
- **Disease and Escape Prevention:** Ponds were disinfected before stocking, and seedlings were bathed in saltwater for 10 minutes. Regular use of quicklime and photosynthetic bacteria helped control diseases.
6. **Harvesting:** Crayfish grow quickly and can be harvested after 1–2 months when they reach 30 grams or more. Harvesting methods included traps, nets, and draining the pond.
7. **Breeding Measures:** By the end of 2006, most shrimps were caught, leaving 200 kg in the pond for breeding. The broodstock grew to about 1.5 cm and required winter insulation to ensure survival.
**Second, Test Results**
1. **Output and Value:** From June to December, 2520 kg of crayfish were harvested, generating 60,480 yuan. Another 1000 kg brought in 60,000 yuan, totaling 120,480 yuan in revenue.
2. **Economic Benefits:** Total costs included 56,400 yuan for various expenses, including seedlings, feed, and maintenance. Net income reached 64,080 yuan, with a profit of 5,340 yuan per acre.
**Third, Discussion and Summary**
1. The market price of Procambarus clarkii has been rising, with wholesale prices reaching 30 yuan/kg. Demand remains high, and the government encourages its cultivation due to its strong international competitiveness.
2. Planting aquatic vegetation and introducing snails are essential for providing habitat, food, and water quality improvement.
3. Timely harvesting of large individuals helps reduce overcrowding and promotes faster growth.
4. Breeding should focus on females, as males can store sperm for several months, ensuring successful reproduction.
5. Fresh feed and properly cooked waste are critical for disease prevention. Adding dehulling agents supports proper molting and growth.
This comprehensive approach has proven effective in raising Procambarus clarkii, offering a profitable and sustainable aquaculture option.