Four key technical points for pond farming of crayfish

In recent years, with the sharp increase in the crayfish consumption market and the growth of export processing, prices have been rising, which has also led to increasingly intensive harvesting of wild crayfish and fewer and fewer wild resources, making artificial farming of crayfish imperative. Crayfish have strong adaptability, do not have high requirements for environmental conditions, and can reproduce naturally, so crayfish farming can be adapted to local conditions with diverse models. Farming crayfish in ponds requires mastering four key technical points.

I. Key technical points for pond farming of crayfish

1. Pond clearing and preparation

Ponds for raising crayfish require sufficient water sources, good water quality, and convenient water intake and drainage. The top width of the pond embankment should be more than 1 m, with a slope of 1:3. An area of 3—8 mu is suitable, rectangular in shape, with a water depth of 1—2 m. Newly excavated ponds and old ponds should, depending on the situation, have the pond bottom leveled, silt removed, and the pond dried, so that the pond bottom and walls have good water retention performance and leakage of pond water is reduced as much as possible. While clearing and preparing, use 60—80 cm high netting to enclose the pond embankment around the pond, and the upper end of the netting should also be sealed with 20—25 cm plastic film to prevent entry of harmful organisms and later escape of crayfish.

Crayfish are benthic crawling animals. What determines pond yield is not the volume of the pond water body, but the horizontal area of the pond and the degree of winding of the embankments. That is, for ponds of the same area, the larger the horizontal area in the water body and the greater the length of the embankment sides, the more crayfish can be stocked and the higher the yield. Therefore, 1—20 m from the pond embankment around the pond, 2—3 layers of platforms can be built in parallel with netting or bamboo mats. The first layer is set 20—30 cm below the water surface, 2—3 m long and 30—50 cm wide, with a distance of 20—30 cm between the two layers. Each layer of platform has a slope leading to the pond bottom; between two parallel platforms, a gap of 1—2 m should be left for crayfish to move into the shallow water area. At the same time, a certain number of vertical netting pieces should be set up in the middle of the pond.

2. Pond clearing and disinfection

Clearing and disinfecting the pond can effectively kill harmful organisms in the pond such as catfish, snakehead, snakes, rats, and so on, wild and miscellaneous fish that compete for food such as carp and crucian carp, as well as pathogenic bacteria. The commonly used methods mainly include: 1) Quicklime disinfection: quicklime can be used for dry disinfection and disinfection with water. Dry disinfection method: use 50-100 kg of quicklime per mu, sprinkle it over the whole pond, then after 3—5 days of drying the pond, fill with new water. Disinfection with water method: based on 1 m water depth per mu of water surface, use 125—150 kg of quicklime dissolved in water, then sprinkle evenly over the whole pond. 2) Bleaching powder disinfection: after completely dissolving bleaching powder, sprinkle it evenly over the whole pond, with a dosage of 20—30 kg per mu (containing 30% effective chlorine).

3. Planting aquatic plants

Crayfish are omnivorous, and the aquatic plants they feed on include Elodea, hornwort, Hydrilla verticillata, water hyacinth, and water peanut. Planting aquatic plants in about 10%—20% of the shallow water area around the pond can not only provide food for crayfish, but also provide an ideal place for concealment and habitat, and is also a good place for crayfish to molt. “How many shrimp there are depends on the aquatic plants.” In ponds with many aquatic plants, the survival rate of raised shrimp is high. However, the planting area of aquatic plants should not be too large, otherwise, because the aquatic plants are too luxuriant, they will cause oxygen deficiency in the pond water at night and affect the normal growth of crayfish, and also affect harvesting. Generally, the area planted with aquatic plants should preferably not exceed 1/4 of the total pond area. In addition, at the bottom of the pond, aquatic plants can be tied into bundles, with one bundle placed every 5 m, 5-10 kg of aquatic plants per bundle, sunk to the bottom, with 20—40 bundles per mu, each bundle tied with a rope, and the other end of the rope floating on the water surface or fixed at the water surface.

4. Water intake and fertilization

The water source should have fresh water quality, sufficient dissolved oxygen, and no organic matter or industrial heavy metal pollution. When injecting new water into the pond, it should be filtered with 20-40 mesh gauze to prevent wild fish and fish eggs from entering the rearing pond with the water flow. At the same time, fertilize to cultivate plankton, so as to directly provide natural feed for young shrimp after they enter the pond. When fertilizing the shrimp pond, it is best to use organic fertilizer, such as applying fermented organic grass manure, with an application rate of 100—200 kg per mu, so that the pond water has a certain fertility. In the early stage of young shrimp stocking, the pond water level is relatively shallow and the water quality is relatively fertile; in the middle and late stages of rearing, as the water level deepens, the amount of fertilization should be gradually increased. Specifically, it should be determined according to water color, keeping the pond water transparency at 35-40 cm.

II. Crayfish farming costs

1. Land rent. At present, land rent levels vary across all regions of the country, generally around 600-1000 yuan, so 800 yuan/mu is used as the middle figure for calculation.

Land infrastructure construction costs: mainly including the construction of farming pond ditches, land leveling, and other infrastructure, with a cost of about 400-500 yuan per mu; it will vary depending on land conditions in each region. If land leveling is needed, the cost will increase several times, so when leasing land, choose areas with level land to reduce unnecessary construction costs as much as possible.

2. Ground cages: each mu needs 10 short ground cages or 5 long ground cages, costing 150-200 yuan;

3. Work sheds and office space: depending on whether the farming area is contiguous, for large-area contiguous farming, 40-50 yuan per mu;

4. Water conservancy facility construction: mainly including the construction of water intake and drainage ditches within the farming park, and the cost of irrigation and drainage equipment; at the most basic level, each farming pond needs independently buried water intake and drainage pipes, and water intake and drainage ditches need to be built or widened, at a cost of 50-80 yuan per mu. Depending on local water intake and drainage facilities, there will be slight differences, so when choosing land, choose land with convenient irrigation and abundant water sources; otherwise, the water source needed for farming each year will also be a considerable expense;

5. Anti-escape facilities: mainly the anti-escape nets around the farming ponds and the anti-theft nets around the park, plus labor costs, about 10 yuan per mu.