A Detailed Guide to Crayfish Pond Aquaculture Methods and Precautions
With the continuous development of China's aquaculture industry, crayfish farming has become increasingly common, especially since in recent years China's late-night snack industry has been developing rapidly, and many restaurants specializing in crayfish have continued to spring up, so the demand for crayfish has also been rising.
Crayfish Pond Aquaculture Methods and Precautions
1. Pond clearing and preparation: A pond for raising crayfish requires an adequate water source, good water quality, and convenient water intake and drainage. The pond bank should have a top width of more than 3 m and a slope of 1:3. An area of 3 to 5 mu is suitable, rectangular in shape, with a water depth of 1 to 2 m. Newly dug ponds and old ponds should, depending on the situation, have the pond bottom leveled, the silt removed, and the pond dried, so that the pond bottom and walls have good water-retention properties and water seepage is reduced as much as possible. While clearing and preparing the pond, use 60 to 80 cm high netting to enclose the pond banks around the pond, and the upper edge of the netting should also be enclosed with 20 to 25 cm plastic film, to prevent entry by harmful organisms and the later escape of crayfish.
Crayfish are benthic crawling animals, and what determines pond yield is not the volume of the pond water body but the horizontal surface area of the pond and the degree of irregularity of the pond banks. That is, for ponds of the same area, the larger the horizontal surface area and the greater the length of the bank perimeter, the more crayfish can be stocked and the higher the yield. Therefore, 1 to 2 m from the pond banks, 2 to 3 layers of platforms can be set up in parallel using netting or bamboo mats. The first layer is set 20 cm below the water surface, 2 to 3 m long and 30 to 50 cm wide, with a distance of 20 to 30 cm between the two layers, and each platform has a slope leading to the pond bottom; a gap of 100 to 200 cm should be left between two parallel platforms, for crayfish to move into the shallow-water area. At the same time, a certain number of vertical netting panels 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, loach, snakehead, snakes, rats, and so on; wild and miscellaneous fish that compete for food such as carp, crucian carp, and so on; as well as pathogenic bacteria. The commonly used methods are mainly:
3. Quicklime disinfection: Quicklime disinfection has two types, dry method and water method. Dry method: use 50 to 100 kg of quicklime per mu, splash it over the whole pond, then after 3 to 5 days of pond drying, fill with fresh water. Water method: calculated at a water depth of 1 m per mu of water surface, use 125 to 150 kg of quicklime dissolved in water, then splash it evenly over the whole pond.
4. Bleaching powder disinfection: After fully dissolving the bleaching powder, splash it evenly over the whole pond, with a dosage of 20 to 30 kg per mu; the dosage of bleaching concentrate is halved. Planting aquatic plants: Crayfish have omnivorous feeding habits, and the aquatic plants they feed on include pondweed, hydrilla, water hyacinth, water lettuce, and water peanut, among others. Planting aquatic plants in about 10% to 20% of the shallow-water area around the pond can provide food for crayfish, while also providing an ideal place for the shrimp to hide and rest, and a good place for crayfish to molt. "The more shrimp, the more plants to check," and ponds with abundant aquatic plants have a high survival rate for shrimp farming. However, the planting area of aquatic plants must not be too large, otherwise, because the aquatic plants are overly lush, they will cause oxygen deficiency in the pond water at night and affect the normal growth of crayfish. Generally, the area planted with aquatic plants should not exceed 1/5 of the total pond area. In addition, at the bottom of the pond, aquatic plants can be tied into grass bundles, placed one bundle every 5 m, with each bundle containing 5 to 10 kg of aquatic plants, sunk to the bottom, with 20 to 40 bundles per mu. Each bundle is tied with a rope, and the other end of the rope floats on or is fixed at the water surface.
5. Water intake and fertilization: The water source requires fresh water quality, sufficient dissolved oxygen, and no organic matter or industrial heavy metal pollution. When injecting new water into the pond, filter it with 20 to 40 mesh gauze to prevent wild miscellaneous fish and fish eggs from entering the rearing pond with the water flow. At the same time, fertilize to cultivate plankton, 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 fermented organic grass manure. The application rate is 100 to 200 kg per mu, so that the pond water has a certain fertility, maintaining the pond water transparency at 35 to 40 cm.
What Is Crayfish
Crayfish is also called red swamp crayfish, red claw crayfish, and freshwater crayfish. It resembles a shrimp but has a hard shell. Adults are about 5.6 to 11.9 cm long, dark red, with part of the shell nearly black, and a wedge-shaped stripe on the back of the abdomen. Young shrimp are uniformly gray, sometimes with black ripples. The claws are narrow and long. The middle of the shell is not divided by net-like gaps, and the shell is clearly granular. The rostrum has lateral spines or the tip of the rostrum has notches.
It is a freshwater economic shrimp species, widely welcomed by people for its delicious meat. Because of its omnivorous diet, fast growth rate, and strong adaptability, it forms an absolute competitive advantage in the local ecological environment. Its feeding range includes aquatic plants, algae, aquatic insects, animal carcasses, and so on, and when food is scarce it also cannibalizes its own kind. In recent years, crayfish has become an important economic aquaculture species in China. In commercial farming, escape must be strictly prevented, especially escape into pristine water bodies rarely visited by people. Its ecological competitive advantage over local species leads to destructive harm.
Feeding Management for Crayfish Culture in Rice Fields
1. Feed feeding
In rice-field shrimp farming, feeding should be done at fixed times, fixed locations, fixed amounts, and fixed quality as much as possible. Crayfish have omnivorous feeding habits and eat both meat-based feed (small miscellaneous fish, snail meat, river meat, fish meat, earthworms, animal offal, silkworm pupae), concentrated feed (sugar cake, corn, wheat, barley meal), and green feed (various aquatic grasses, vegetable scraps, and so on). The daily amount put in is generally 4% to 6% of the shrimp body weight. In the early stage, feed twice a day, once in the morning and once in the afternoon; in the later stage, feed once at around 18:00.
2. Water and fertilizer management
After the crayfish are stocked, field ditch management is a very important link. The water depth in the rice field should be maintained at about 20 cm, and water injection is generally carried out from 10:00 to 11:00, keeping the temperature of the incoming water close to the water temperature of the rice field.
During rice field management, the water level should also be regulated according to the requirements of rice field drying and pest control. In the middle stage of rice growth, dry the field appropriately, thereby increasing light, increasing root vitality, sterilizing and raising temperature. At ordinary times, flood control, drainage, and anti-escape work must also be done well. After heavy rain, promptly check whether the water inlet and outlet and the shrimp-blocking facilities are intact, to prevent shrimp escape.
3. Disease and natural enemy control
Adhere to the principle of prevention first and combining prevention with control. During rice growth, pesticides must be sprayed for pest control; after spraying pesticides, replace with fresh water, thereby providing the necessary ecological environment for the growth of rice and crayfish. For rice disease control, mainly use high-efficiency, low-toxicity pesticides, adopt the spray method, so that the pesticide falls on the leaf surface, and choose a windless sunny day from 8:00 to 9:00 as the application time. Once natural enemies are found, eliminate them promptly, and at the same time install fine-mesh nets at the water inlet and outlet to prevent harmful organisms from entering.
Misconceptions to Avoid in Crayfish Farming
1. Regarding seedlings: What is currently called crayfish can also be called red swamp crayfish or Japanese red swamp crayfish, all of which are one species; there is no such thing as a "hybrid variety," because the cost is too high and natural seedlings are currently abundant and cheap, while artificial seedlings are still at the laboratory stage; in addition, do not mistakenly believe it is a new variety that has been domesticated and has less mutual cannibalism, and thus buy crayfish seed from other places at a high price.
Many people believe that as long as seed crayfish are put in in the first year, through continuous reproduction on their own, good returns can be obtained every year. In fact, crayfish farming has the highest yield in the first year of seed stocking, and then declines year by year. Because the crayfish life cycle is 16-18 months, and inbreeding leads to functional degeneration and reduced disease resistance, after 3 years the yield will drop sharply or even fail completely.
2. Regarding water quality: Some people think that crayfish can also grow very well in smelly ditches, but in fact it is not that they can be raised in both good and bad water; fresh water quality is the key to high-yield crayfish farming. It is required that the coverage of aquatic plants in the pond be 30%-60%. Water transparency should be around 30 cm, dissolved oxygen >5 mg/L, and water should be changed regularly, with 1/3 changed each time, and the water level kept above 80 cm in high-temperature seasons.
3. Regarding feed: Crayfish are organisms with omnivorous feeding habits that lean toward animal-based bait, and whether they grow well depends on protein intake. Fresh small miscellaneous fish and river snails can be used as the main feed, supplemented by plant-based bait, and compound feed with a protein content of no less than 32% can also be fed. Rotten and spoiled animal and plant feed should not be fed, because its utilization rate is low and it easily deteriorates water quality.
In the process of farming crayfish, in addition to understanding the living habits of crayfish, mastering its farming techniques is also very important, and generally crayfish are pond-farmed, so in the process of farming crayfish, the pond environment is also quite important.