A reader from Guanzhen Town, Yuxian County, called in and mentioned that he had stocked 20 kilograms of crabs at a rate of 200 per kilogram in his 10-acre crab pond. He asked whether it would be possible to also introduce some crayfish into the same pond and, if so, how many crayfish should be added per acre.
According to Chen Huangen, head of the promotion department at the Jiangsu Provincial Aquatic Technology Promotion Station, introducing crayfish into a crab pond is not without risks. Crayfish and crabs compete for oxygen, aquatic plants, and food. Both species also have a tendency to fight and even mutilate each other. Traditionally, crayfish are not commonly introduced into crab ponds due to these potential issues. However, based on practical experience, it is possible to raise both species together under certain conditions.
To successfully raise crayfish in a crab pond, the following measures should be taken:
1. **Ensure sufficient plant coverage.** Since both crabs and crayfish feed on aquatic plants, it's crucial to maintain more than 50% plant coverage in the pond. This helps reduce competition between the two species. It's best to introduce crayfish after the plants have fully grown.
2. **Provide enough feed.** Proper feeding is essential to prevent aggression and cannibalism between crabs and crayfish. Accurate knowledge of the population in the pond is necessary. When feeding, ensure there is enough food available, including fresh snails. For every mu (approximately 667 square meters), at least 250 kg of fresh snails should be provided, ideally between 250–500 kg. The feeding principle should follow “two fine and one thick,†meaning feed small amounts frequently and avoid overfeeding. If large quantities of feed are used, water quality must be closely monitored to prevent deterioration, which could lead to the death of both crabs and crayfish.
3. **Fertilize the water early.** In the initial stages of crayfish farming, apply an appropriate amount of base fertilizer to promote the growth of zooplankton, which serves as a natural food source for the crayfish.
Typically, a stocking density of 2,000–3,000 crayfish per acre is recommended. Overstocking can lead to breeding failure. During the growing period, use traps or cages to catch and remove larger crayfish, keeping their population low in later stages to ensure the healthy growth of crabs.
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