High-yield and high-efficiency polyculture technology for river crabs and red swamp crayfish
Since Jianyang Town in Jianhu County began implementing the fishery science and technology outreach program in 2006, it has vigorously promoted the technology of polyculturing red swamp crayfish in crab ponds, producing a large number of exemplary science and technology demonstration households. For example, demonstration household Chen Lüsheng in Xinyang Village implemented polyculture of red swamp crayfish in crab ponds in 2008, with a farming area of 80 mu, an average yield per mu of 60 kg of river crabs of 150 g or more, with the largest male river crab individual reaching over 300 g; 65 kg of red swamp crayfish per mu, with individuals weighing around 40 g, and a net profit of 2,596 yuan per mu, greatly improving the efficiency per unit area and achieving high yield and high efficiency. This article will briefly introduce the high-yield and high-efficiency polyculture technology for river crabs and red swamp crayfish.
1. Pond conditions
The pond requires convenient water inlet and drainage, maintaining a water depth of 1-1.5 m, a pond slope ratio of 1:3, and a 0.6 m high anti-escape wall built with asbestos tiles around the pond field. Every December, drain the pond water, and use 100-150 kg of quicklime per mu for pond clearing and disinfection. The sludge at the bottom of the pond should be removed after being dried in the sun. The removed sludge, after being dried and disinfected, can be used to reinforce the embankments. The embankments should be made high and wide. A small inner embankment should be added on the inner side of the large embankment, with the small embankment about 50 cm wide and 30 cm lower than the large embankment, providing red swamp crayfish with places to dig burrows for mating and spawning. The pond is equipped with 1 set of aeration-type oxygen-increasing machine.
2. Planting aquatic plants and stocking snails
In ponds for culturing crayfish and crabs, plant a certain amount of Elodea and appropriately mix in other submerged plants. Plant water peanut along the pond edges. The area of aquatic plant planting should be 1/4 to 1/3 of the pond area. Aquatic plants should be planted in strips, with a row spacing of 3-4 m and a plant spacing of 2-3 m. If the aquatic plants are planted too densely, it will cause oxygen deficiency in the pond at night, and during high temperatures it is likely to cause the pond water to become turbid. The aquatic plants will rot due to high temperature and light, causing deterioration of water quality and causing disease in crayfish and crabs. Snails are a high-quality animal feed for river crabs and red swamp crayfish. Stock 300 kg per mu. It is best to use locally caught snails, preferably stocked on the same day they are caught, to ensure the survival rate of the snails.
3. Seedling and fingerling stocking
In mid-March, stock 500 juvenile crabs per mu with a robust physique, no disease or injury, and a size of 80-100 individuals/kg. In early April, stock 6 kg per mu of red swamp crayfish juveniles with a robust physique, uniform size, and 300 individuals/kg, stocking the full amount at once. In the following year, except for stocking river crab seedlings, there is no need to stock red swamp crayfish seedlings again.
4. Feed feeding
River crabs and red swamp crayfish both belong to the order Decapoda, and their habits and feeding habits are relatively similar. Therefore, river crab feed can be used as the main feed, fed at fixed points every day, with a daily feeding amount of 5% of the total body weight of river crabs and red swamp crayfish in the pond. In the morning, feed wheat, soybean meal, and rapeseed meal; in the afternoon, feed complete formula pellet feed, letting the crayfish and crabs eat their fill and eat well. Also, appropriately fertilize the water to benefit the growth and molting of crayfish and crabs. In the early stage of culturing, feed complete formula feed with a protein content of about 40%; in the middle stage during the high-temperature season, feed complete formula feed with a protein content of 28%; in the later stage starting from August, feed complete formula feed with a protein content of 40% again to fatten the river crabs.
5. Water quality management
From March to April, focus on water testing, keeping the water level at 0-30 cm to increase light exposure, raise water temperature, promote aquatic plant growth, and accelerate the growth and molting of red swamp crayfish. In May, as the temperature rises, the water level gradually increases to the highest water level. Every 15 days, use 20 kg of quicklime per mu for disinfection once. In addition, according to the water quality conditions in the pond, exchange fresh water, draining first and then filling, exchanging 1/3 of the water each time, 2-3 times per month. After the temperature drops in autumn, the water level gradually decreases, enabling parent red swamp crayfish to dig burrows in time for mating and rearing offspring, increasing the red swamp crayfish population for the next year.
6. Daily management
6.1 Take good anti-escape and anti-theft measures, patrol the pond daily, observe the feeding activities, growth, and molting of crayfish and crabs, and promptly handle any problems found.
6.2 Maintain appropriate aquatic plants in the pond to provide habitat for crayfish and crabs and concealment during molting, preventing them from killing each other.
6.3 Feed must be sufficient. Only when crayfish and crabs eat their fill and eat well can they grow quickly, reach large sizes, and achieve high yields.
6.4 When preventing disease and treating pests, it is prohibited to use harmful drugs such as pyrethroids and trichlorfon to prevent harm to red swamp crayfish. When using drugs to kill ciliates, avoid the peak molting period.