In the summer, the weather becomes hot, and water temperatures rise significantly. To ensure that river crabs can safely cross the river and improve their survival rate, several key measures must be implemented:
First, it's essential to provide sufficient aquatic vegetation. The crab pond should be stocked with plants like water hyacinth, duckweed, reeds, and other native species. Where possible, use bricks or tiles to create artificial shelters for the crabs, offering them a cool and safe resting place. Additionally, maintain a good supply of young weeds such as *Hydrilla verticillata* and *Arthrobacter* species, which serve both as food and protection from predators. However, the shaded plants should not cover the entire surface of the pond—only about one-third of the area should be covered to allow proper sunlight penetration and oxygenation. Regularly remove any dead or dirty plants to prevent water pollution and the growth of harmful bacteria.
Second, maintaining clean water and adequate nutrition is crucial. The pond should be regularly monitored for water quality, and leftover food and debris should be removed promptly. Keep the water depth above 1 meter and perform water changes frequently. It's best to change the water in the evening, always leaving at least one-third of the original water as bottom water. During high-temperature periods, shorten the interval between water changes. Normally, a water change every 3 to 5 days is recommended. The water source must be clean and free from contamination.
To support crab growth, the water should contain certain inorganic salts, especially calcium ions, which are vital for shell development. After each water change, add appropriate amounts of inorganic salts based on the pond conditions. For example, applying 5–10 kg of quicklime per 667 square meters after water exchange can help strengthen the crabs' shells. Small quantities of other minerals may also be added during this period.
Third, feeding practices need to be carefully managed. Increase the proportion of plant-based feed while reducing animal-based food. Crabs enjoy foods like wheat, pumpkin, and soybean cakes. These should be prepared into small lumps and placed on feeding platforms to make observation easier and avoid water pollution. The amount of food should be adjusted based on the daily water temperature and the crabs’ previous day’s feeding behavior. Typically, feed around 10% of the total crab weight, allowing a slight surplus for two hours after feeding. Feeding should take place daily between 4 and 5 PM to align with the crabs’ nocturnal habits.
Finally, effective escape prevention and disease control are critical. During the hot season, regular pond inspections are necessary. By patrolling the pond, you can monitor crab activity, check the condition of escape barriers, and identify signs of disease or predators. If any signs of escape are found, repair or replace damaged structures immediately. Capture and remove predators like frogs and water rats to protect the crabs. River crabs are prone to various diseases, so regular preventive treatments using disinfectants like bleaching powder should be applied. Any sick or dead crabs should be examined promptly, and appropriate actions taken to prevent the spread of illness.
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