Master freshwater crayfish farming techniques: a guarantee of wealth through crayfish farming next year

Hefei is a famous land of fish and rice in China, home to Chaohu Lake, one of China's five largest freshwater lakes, with a relatively large water area reaching 153,000 hm2. Hefei is very rich in water resources and is a major fishery city in Anhui Province. Changfeng County, Feixi County, Feidong County, Chaohu City and Lujiang County were awarded the title of "2013 Anhui Major Aquaculture County", and Changfeng County was selected as an Anhui Major Aquaculture County for the first time. Based on years of practical work in aquatic technology, the author has summarized crayfish farming techniques.

1 Preparation of farming facilities

For ponds, a depth of 1-2 m and an area of 3,335-6,670 sq m are suitable, with a flat pond bottom, preferably loam soil, requiring relatively hard soil and easily controlled water level. The pond water must be pollution-free, with ditches that can drain and fill, following the principle of high-level irrigation and low-level drainage, and the pond should have good water retention. In addition, because crayfish easily escape, escape-prevention facilities are usually built with calcium plastic or plastic film, and escape-prevention netting is set up around the pond with wooden or bamboo stakes. The height of the enclosure is 60-70 cm, buried about 20 cm into the ground.

2 Pond clearing and disinfection

There are 2 methods for pond disinfection: first, bleaching powder disinfection, with a dosage of 450 kg/hm2; after the bleaching powder is completely dissolved, spray the entire pond [1]; second, quicklime disinfection, with a dosage of 750-1,500 kg/hm2; leave 5-10 cm of water in the pond, dissolve the quicklime and spray the entire pond, stir the pond bottom the next day, and after 3-5 d, dry the pond.

3 Applying sufficient base fertilizer

Applying sufficient base fertilizer has two effects: on one hand, it can promote the reproduction of zooplankton and algae, and plankton can serve as feed for shrimp fry, promoting the growth of shrimp fry [2]; on the other hand, it can stabilize water quality. However, attention should be paid to the dosage and method of fertilization. The correct application method is to bury the fertilizer into the mud at a depth of 15-20 cm, and it must not be directly sprinkled into the pond water, so as to avoid water pollution. If the pond has little silt or is newly dug, more should be applied, with an application rate of 1,500-4,500 kg/hm2; if the pond silt is relatively thick, then do not apply or apply less. Biological organic fertilizer is best, followed by cow dung, chicken manure or pig manure.

4 Planting aquatic plants

Planting aquatic plants in ponds has major effects: first, aquatic plants can provide habitat and climbing surfaces for crayfish, playing a role in optimizing ecology and providing greater concealment, reducing bullying of the weak by the strong; second, aquatic plants can serve as feed for crayfish, and the coverage of aquatic plants in the pond should be no less than 60%; third, they can purify the water body, balance the water environment, absorb harmful substances in the water, and resist wind and waves [3]. Aquatic plant species include water hyacinth, alligator weed, tape grass, Elodea, water chestnut grass, Hydrilla and other aquatic plants. The planting area of aquatic plants should preferably account for 50% of the pond area. If conditions permit, some tree roots, bamboo tubes, empty cans and the like can also be placed at the bottom of the water body; these are the favorite habitats of crayfish.

5 Stocking of shrimp fry and shrimp seed

Changfeng County mostly adopts summer stocking, in mid-to-late July, mainly with the first batch of young shrimp hatched that year, with a stocking rate of 450,000-600,000 tail/hm2, and young shrimp size above 0.8 cm. There are strict quality requirements for seedlings and seed: first, strong physique, free of disease and injury, and strong vitality; second, shrimp fry and shrimp seed are all artificially bred, and wild seed needs to be domesticated before stocking; third, uniform size, and the shrimp fry and shrimp seed stocked in the same pond must be of consistent size, with shrimp seed size around 3 cm and young shrimp size above 0.8 cm.

The following points should be noted for shrimp fry stocking: first, in order to kill pathogenic bacteria and parasites, they should be bathed in 3%-5% salt water for 10 min before stocking; second, for shrimp seed purchased from elsewhere, they need to be soaked for 1 min first, then lifted and left for 2-3 min, repeated 2-3 times, to increase the survival rate; third, for summer stocking, choose cloudy and rainy days or sunny mornings to reduce exposure to sunlight; fourth, in order to improve pond water quality and make full use of feed resources, silver carp and bighead carp can be stocked in the pond [4].

6 Scientific feeding

First, feed according to the living habits of crayfish. Because crayfish mostly like to be active at night, feed once in the morning and once in the afternoon, with the afternoon feeding as the main one, accounting for about 70% of the total food intake. When feeding, adopt the feeding method of fixed quantity, fixed time and fixed quality, ensuring sufficient and even feeding, ensuring each shrimp is well fed, and reducing food competition among young shrimp. Second, feed according to the feed requirements of crayfish at different developmental stages. First, the young shrimp and juvenile shrimp stage. At this stage, they mainly feed on aquatic insect larvae and cladocerans, rotifers, copepods and the like; second, the adult stage. They feed on plant-based feed and animal-based feed. In addition, during the crayfish growth season from August to October, feed more green feed and soybean cake, and appropriately feed some animal-based feed; in winter, mainly feed animal-based feed. After crayfish are stocked, additional fertilizer should be applied to the water body to fertilize the water quality [5]. Third, feed according to weather conditions and changes in water quality. The suitable growth temperature for crayfish is 20-32 °C. In May-June or August-October, crayfish have a large food requirement, so feed more dry feed or mixed feed. However, during continuous cloudy and rainy days or when the water quality is too dense, feed less; when the weather is clear and good, feed more; when crayfish are molting, feed less, and after molting, feed more [6].

7 Daily management

First, conduct inspections every day and deal with abnormal situations in a timely manner; second, regulate water quality, change the water once every 15-20 d, and maintain the pH value at 7.0-8.5; spray quicklime water once every 20 d, with a dosage of 150 kg/hm2. At the same time, keep the water level stable and not fluctuating suddenly; third, manage the molting sites, strictly prohibit disturbance when a large number of shrimp are molting, and increase palatable feed to prevent mutual cannibalism.