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Key Techniques for Cultivating Middle-aged Shrike Crab
Scylla serrata, commonly known as the blue crab, is a highly valued species in aquaculture due to its fast growth, strong adaptability to varying temperatures and salinity levels, delicious meat, nutritional value, and high economic potential. In China, the culture of Scylla serrata has a long history, with breeding practices dating back over a century. Initially used for fattening and stocking, the industry experienced significant growth since the 1980s, especially in coastal provinces like Fujian, Guangdong, Zhejiang, Guangxi, and Hainan. As aquaculture techniques advanced, the scale of blue crab farming expanded, leading to increased production efficiency and a more established industry.
Despite this progress, the current supply of seedlings remains heavily dependent on wild catches, with very few commercially produced crabs available. This shortage of quality seedlings poses a major challenge to the industry's sustainable development. According to Blackshaw (1999) in his book "Mud Crab Aquaculture & Biology," the availability of seedlings remains a critical constraint in blue crab farming, emphasizing the need for further research into artificial breeding techniques.
Since the late 1980s, researchers at Xiamen University have made significant strides in studying the reproductive biology and artificial breeding of blue crabs. They achieved breakthroughs in cultivating larvae and developed a complete process for producing seedlings. By the mid-1990s, mass production became possible, but challenges remained. Most farmers only raise juvenile crabs, skipping the crucial stage of large-eyed larvae, which significantly lowers metamorphosis rates and limits the scalability of artificial breeding.
The technical complexity of raising blue crabs from large-eyed larvae to marketable juveniles presents another barrier. To address this, Xiamen University focused on improving breeding models and promoting the cultivation of early-stage juveniles. This innovation helped spread advanced techniques across southern China, advancing the industry significantly. However, standardization of cultivation methods and improved breeding techniques are still needed for consistent results.
The intermediate cultivation of blue crab seedlings involves raising large-eyed larvae to small crabs of 1.2–1.8 cm in size. This step is essential for ensuring that artificial seedlings can be effectively used in farming. Success in this phase increases survival rates, enhances economic returns, and promotes industry growth. Key factors include proper pond construction, water quality management, feeding strategies, and disease prevention.
Ponds for intermediate cultivation can be concrete or earthen, located near hatcheries with access to clean water. They should be equipped with hiding structures such as oyster shells or palm pieces to reduce stress and predation. Before stocking, pools must be disinfected using bleach or lime, followed by the introduction of filtered seawater. Stocking density and timing are also important, with careful attention to temperature differences and gradual salinity reduction.
Feeding is a critical aspect of daily management. Early stages rely on live feeds like Artemia and copepods, transitioning to frozen food and commercial feed as crabs grow. Water quality parameters—such as salinity, temperature, pH, and dissolved oxygen—must be closely monitored to maintain optimal conditions. Regular removal of debris and uneaten food helps prevent pollution and disease outbreaks.
Disease prevention is equally vital. Maintaining clean water, using appropriate disinfectants, and enhancing the crabs’ immunity through nutrition are key strategies. Daily observations of water quality, crab behavior, and pond conditions ensure timely intervention when issues arise.
Overall, the success of blue crab aquaculture depends on continuous improvement in breeding techniques, better seedling supply, and effective management practices. With ongoing research and refinement, the industry can achieve greater stability, sustainability, and profitability.