Through thorough research, investigation, and analysis of several breeding units, along with a comparison of their farming methods, it has been found that the current polyculture model involving crayfish, crabs, and fish is quite efficient and yields substantial benefits. To successfully implement this polyculture system, the following key technical points should be carefully considered and followed.
First, it's essential to properly disinfect the ponds before stocking and to install effective anti-escape facilities. This ensures a clean environment and prevents the loss of aquatic species.
Second, the planting and transplantation of aquatic vegetation should be emphasized. A balanced mix of submerged, floating, and emergent plants should be maintained in the pond. The total area covered by aquatic plants should not exceed one-third of the pond’s surface area, which helps provide shelter and improve water quality.
Third, selecting the right combination of species is crucial. In a crayfish and crab polyculture system, it is common to introduce species such as silver carp, grass carp, and squid. A small number of carp can also be added to serve as live feed for larger fish. However, the size of these carp must be carefully controlled to avoid overstocking or competition.
Fourth, introducing live snails into the pond can be beneficial. They act as a natural food source for shrimps and crabs while also helping to maintain good water quality by consuming organic matter.
Fifth, feeding practices should be adjusted seasonally. During spring, concentrated feed should be provided to promote rapid growth of crayfish. It's important to ensure that all marketable crayfish are harvested by the end of June to prevent any negative impact on crab growth. The feed formula should be well-balanced—preferably made on-site—and processed into pellets. This not only increases feed efficiency and reduces costs but also minimizes water pollution and supports disease prevention.
Sixth, maintaining good water quality is vital. Regular water exchanges should be carried out, and the water transparency should be kept around 30 cm in the early stages and 40 cm in later stages. Water quality improvement agents should be used periodically to keep the pond environment healthy.
Lastly, when harvesting crayfish, appropriate nets should be used to minimize harm to crabs. After setting up the net, crabs should be quickly returned to the pond, followed by sorting out other species. Care should also be taken to preserve the next generation of shrimp during the harvesting process.
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