Crabs can only grow when they molt, which is a critical phase in their development. For successful molting, crabs need to be in the right environment. This includes shallow water, low light intensity, a quiet setting, clean and fresh water, and access to a wide variety of high-quality, palatable food. If these ecological conditions are not met, crabs may fail to molt or even die without successfully shedding their old shell. During the molting process, there are several key points to monitor:
First, observe the crab’s body color and feeding behavior. Before molting, the crab's body color becomes darker—often deep yellow-brown or dark brown. Their legs feel hard, and the plastron (the underside of the shell) turns reddish-brown. After molting, the body color lightens, the plastron becomes white, and the legs become soft. Crabs typically stop eating before molting. If, after a few days of feeding, you notice an increase in leftover food and crabs gathering near the shallow areas of the pond, it may indicate that molting has begun. The presence of empty shells is a clear sign that crabs are actively molting.
Second, to ensure synchronized molting, it's important to provide high-quality feed rich in animal protein before large-scale molting occurs. This includes feeds with minced meat and other animal-based ingredients. The proportion of animal feed should exceed 50% of the total diet. It’s essential to maintain good palatability and ensure enough food is available to prevent crabs from preying on soft-shell individuals.
Third, increase the calcium content in the water. Once molting begins, you can add lime (with caution during hot weather) to the water. Apply approximately 7.5 to 10 kg of lime per acre to help sterilize the water and raise calcium levels, which supports shell formation. Additionally, you can sprinkle calcium dihydrogen phosphate at a rate of 0.75 to 1 kg per acre.
Maintain a stable water level. Before molting, it’s beneficial to flush or change the water slightly to stimulate the process. However, once crabs enter the active molting stage, it’s best to keep the water level constant and avoid frequent changes.
Finally, strengthen daily management. Regularly remove floating debris and rotten aquatic plants. Adjust feeding amounts appropriately during molting, and avoid feeding in dense molting areas. If soft-shell crabs are found during routine checks, they must be protected. You can gently collect them and place them in buckets for 2 to 3 hours until they regain mobility, then return them to their original location.
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