The release of crab species into river channels can significantly enhance water productivity and improve economic returns. However, in recent years, some farmers experienced low production efficiency due to the practice of monoculture fish farming. Through years of exploration and practical experience, integrating fish and crab polyculture has proven more successful. The average crab yield has reached 10 to 15 kg per unit area, and economic benefits have nearly doubled. Below are the key issues and successful practices observed during the process.
First, selecting an appropriate river ditch is crucial. The water should be clear, fresh, and free from pollution, with a slow current and no major traffic activity. The bottom should be rich in benthic organisms, and aquatic plants should cover about 50% of the area to provide sufficient habitat for crabs.
Second, seed selection and stocking play a vital role. In large-scale river ditch farming, natural food sources are typically used, with minimal or no supplemental feeding. Therefore, fish stocking should follow conventional methods, focusing on stocking fish that year and adjusting grass carp numbers based on plant coverage to avoid competition with crabs. Crab stocking mainly depends on the quality, size, and density of seedlings. Three common sizes are used: small, medium, and large crabs. Based on production cycle and utilization rates, it's most efficient to stock juvenile crabs, followed by third-stage crabs. Seedlings must be healthy, with intact limbs, no signs of disease or injury, and strong responses. Some crabs may mature early, known as "green crabs," which should be avoided as they do not grow further. These crabs have a widened abdomen, dark green shells, and black hairs around the edges. Immature crabs have lighter shells and triangular-shaped females.
Third, proper management is essential. River ditches with good water flow and quality provide ideal conditions for crabs. Under extensive culture, crabs rarely escape, so no need for walls or barriers. However, nets should be placed at both ends of the ditch to prevent crabs and fish from migrating out. Regular checks help monitor growth, and fishing tools like traps and nets can also be used to catch crabs. Daily management includes preventing theft and flood-related escapes.
Fourth, timely fishing is critical. If caught too early, crabs may not meet market size requirements. If delayed, they may escape or lose value. Crabs typically take 6 to 18 months to reach maturity. Around mid-September, when temperatures drop and northwest winds begin, patrols should increase to detect scattered crabs and catch them promptly. Various methods, including cages, nets, and traps, can be used effectively.
Lastly, intermediate holding helps maximize profits. Since crabs are usually harvested between September and October, they often lack plumpness, leading to lower market prices. To address this, crabs can be held for 2 to 3 months after harvest. For every 100 mu of river ditch, 2 to 3 acres of holding pools should be prepared. Proper management, including water quality control and feeding, ensures that crabs gain weight before being sold, significantly increasing economic returns.
Aluminium Steel Co2 Fire Extinguisher
Aluminium Steel Co2 Fire Extinguisher,Portable Co2 Fire Extinguisher,Co2 Portable Fire Extinguisher,Aluminium Alloy Portable Fire Extinguisher
JIANGSU NEW FIRE FIGHTING TECHNOLOGY CO.,LTD , https://www.newayfire.com