In current crab farming practices, the integration of other fish species is commonly carried out alongside large crabs, typically at a density of about 500 per acre. To optimize water usage, it is recommended to introduce 10 to 30 individuals of each species per acre after the initial crab stocking. This includes approximately 5 to 7 kg of heterotrophic silver carp and 2 to 3 kg of green shrimp. Additionally, from May to early June, 15 to 30 small carp can be introduced at a size of 5 to 7 cm per acre. These carp help control wild crabs and shrimp that compete for oxygen, space, and food in the pond, particularly because squid serves as a primary food source for bottom-dwelling species.
Before the first molt of the crabs, careful attention should be given to shallow water breeding, light enhancement, and temperature regulation. Early feeding with small trash fish or high-quality pellets ensures strong shell development during the first molt. Medications and fertilizers should be avoided during peak molting periods to prevent stress on the crabs. It’s important to monitor the molting cycle and plan disinfection one week before the peak. During this time, feed can be supplemented with 1% calcium dihydrogen phosphate, fructooligosaccharides, vitamin C, and Sanhuangsan to support health. Feeding amounts should be reduced during the molting period, and the environment should remain calm to minimize disturbance.
To manage algae growth, maintaining a certain level of water turbidity (around 30–40 cm transparency) helps reduce light availability for moss. Snails should be introduced before the Qingming Festival to promote natural growth and improve water quality. In early stages of moss development, copper sulfate can be used, but care must be taken to avoid harming aquatic plants. Water should be added the following day after treatment. For smaller ponds, manual removal of moss is often more effective.
Maintaining a balanced density of aquatic plants is essential. Submerged plants like Elodea and Vallisneria provide natural food, regulate water temperature, and absorb excess nutrients. Floating plants such as water spinach and water peanuts, along with some emergent plants, create a diverse habitat. The coverage of water grass should be kept between 60% and 70% during the growing season to ensure optimal conditions for crabs.
Snail introduction plays a key role in both nutrition and water quality. Live snails are usually released at 15–200 kg per acre before Qingming to allow them to adapt. A second round of 150–250 kg per acre is added from June to August to maintain a steady supply of natural protein and prevent excessive organic waste that could lead to algal blooms.
Feeding strategies should align with the nutritional needs of crabs at different life stages. A balanced mix of animal and plant-based feeds is recommended, with ratios adjusted over time—60:40 before mid-June, 45:55 from late June to mid-August, and 65:35 from mid-August to October. Enzymatic supplements can be added to compound feed to enhance digestion. Feeding should occur mainly in the evening to ensure crabs consume the feed efficiently, reducing waste and pollution.
Oxygen levels in the pond must be carefully managed. Aeration systems installed at the bottom of the pond help maintain dissolved oxygen levels. Regular water changes are essential, especially from June to September, with water refreshed during sunny afternoons and early mornings. During rainy or hot seasons, chemical oxygenation agents like granular oxygen are used in the evening to maintain water quality.
Water clarity should be maintained at 30–40 cm before May, then increased to over 50 cm afterward. From July to August, water should be changed every 7–10 days, with a 30 cm depth change each time. From September to October, weekly water changes of 1/3 the volume are recommended. pH levels should also be monitored regularly to ensure a stable environment.
Biological agents such as EM bacteria and photosynthetic bacteria are applied four times between July and September, ideally in the morning when aeration is active. Particulate oxygen boosters should be added 1–2 hours later. These biological preparations should not be mixed with disinfectants or antibiotics.
Disease prevention involves regular disinfection with chloral hydrate at 0.3 g/m³ from May to June. From July to September, EM bacterial preparations are used for three consecutive days. Before harvesting, ciliate-killing drugs are applied 20–25 days in advance. Predators such as frogs, rats, and birds should also be controlled to protect the crabs.
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