Sharing Experience on Overwintering Freshwater Crayfish in Aquaculture
As more and more people in China farm crayfish, crayfish farming techniques are also increasing. Farmers can exchange and learn from one another, learning each other's good techniques and methods, so as to maximize the profits of crayfish farming.
How to farm crayfish in freshwater for overwintering
In winter, crayfish enter burrows to overwinter and grow slowly. Strengthening overwintering management of crayfish in winter can improve the overwintering survival rate and farming benefits.
Choose an overwintering pond with an area of 3 mu to 5 mu and a slope ratio of 1:2.5 to 1:3. It should be sheltered from the wind and face the sun, with abundant and pollution-free water, and a water depth of more than 1.5 m. Before stocking the crayfish, drain the pond water and thoroughly disinfect it with 75 kg of quicklime per mu. From 7 days to 10 days before stocking, fill with water and apply fertilizer, spreading 100 kg to 150 kg of decomposed livestock manure per mu to cultivate plankton. Transplant aquatic plants: transplant water hyacinth, alligator weed, Potamogeton malaianus and other aquatic plants into the pond, with a coverage rate of more than 40%, and an even layout. The aquatic plants can absorb excess nutrients in the pond, prevent oxygen deficiency in the pond water through photosynthesis, and at the same time, abundant aquatic plants can breed aquatic insects, supplementing animal protein for the crayfish.
Crayfish stocking techniques
1. Stocking should be carried out on sunny days or overcast and rainy days, avoiding direct sunlight.
2. Purchased crayfish. If they have been out of water for a long time, they should be slightly treated before stocking. That is, soak the crayfish in the pond water for 1 minute to 2 minutes, lift them out and set them aside for 2 minutes to 3 minutes, then soak again for 1 minute to 2 minutes, repeating 2 times to 3 times, so that the crayfish absorb enough water before stocking; this can increase the survival rate.
3. Stocking density. Stock 150 kg to 250 kg per mu, with a size of 16 to 20 crayfish per kg. The crayfish stocked should be strong and robust, uniform in size, with intact appendages, and stocked all at once; avoid stocking in batches to reduce cannibalism.
4. The overwintering pond can be stocked with an appropriate amount of silver carp and bighead carp to regulate water quality and improve feed utilization.
Daily management of crayfish
1. Feed at the right time. Before overwintering, feed more animal feed to strengthen their constitution and improve the winter survival rate. During the overwintering period, crayfish do not forage, but when the weather is clear and warm, they leave their burrows and forage a small amount; at such times, animal feed such as small trash fish and shrimp, snail, clam and mussel meat, and animal offal can be fed in a timely manner to supplement their internal nutrition.
2. Adjust water quality well. During the overwintering period, the water level in the pond should be maintained above 1.5 m to maintain the pond water temperature. If the water level is too shallow, replenish water in a timely manner to prevent the crayfish from freezing injuries or freezing to death; if the water is too fertile, change the water in a timely manner to keep the dissolved oxygen in the water above 4 kg/L and the transparency above 40 cm, preventing the crayfish from dying of suffocation due to oxygen deficiency.
3. Patrol the pond regularly. Patrol the pond twice a day, and take countermeasures in a timely manner if anything abnormal is found. During the overwintering period, every 10 days to 15 days, splash 20 kg of quicklime per mu over the whole pond to disinfect the water body, supplement calcium, and prevent diseases.
Conditions for farming freshwater crayfish 1. The pond should be rectangular, with an area of 1334 to 3335 per sq m being suitable, and a water depth of about 0.9 to 1.5 m. 2. The pond bottom should be hard soil or sandy, without silt, and the pond walls must have a certain slope. 3. The pond must have a good drainage and irrigation system, with water intake at the upper part at one end and drainage at the bottom at the other end; both the water inlet and outlet must have protective screens against predators and escape.
4. The bottom of the pond should have an appropriate area of submerged plant zones, and sufficient artificial hiding structures, such as waste tires, netting, bamboo rafts, etc., for the crayfish to hide and rest. 5. If conditions permit, the pond can be equipped with an aerator. 6. Before stocking the crayfish fry, the pond should be disinfected. If it is a newly built crayfish pond, quicklime can be used to clear the pond with water; if it is an old fish pond for farming, the pond must be dried and disinfected. In addition to splashing quicklime, predatory pest organisms such as loach, catfish, snakehead, and snakes and rats in the pond must also be thoroughly eliminated. Water quality requirements are mainly based on unpolluted surface water from large water bodies such as rivers, lakes and reservoirs as the water source, and groundwater can also be used as the water source. Freshwater crayfish have strong adaptability and can survive within a water pH range of 6.10 to 9.33, but 6.5 to 9.0 is suitable, preferably neutral to slightly alkaline, to facilitate rapid growth of the crayfish. Although freshwater crayfish are tolerant of low oxygen, long-term exposure to low dissolved oxygen will affect their growth rate and survival rate. Pollution of water quality by heavy metals, insecticides, herbicides, oil, methane and the like should also be avoided. In farming, micro-flowing water or regular addition of new water should be adopted, which can promote growth.
Fry stocking and daily management: Fry stocking should be carried out in the early morning or evening of a sunny day. Before stocking, first slowly add a small amount of pond water to the transport container to adjust the water temperature, until the water temperature in the container is close to the pond water temperature, then put the fry into the pond. The stocking density is 7.5 to 9.0 fry per sq m, and the fry stocked in the same pond are required to be uniform in size. Because freshwater crayfish grow quickly, have vigorous metabolism, and consume a lot of oxygen, the water quality of the crayfish pond should be kept fresh regularly; generally, add 15 cm to 20 cm of water each week to keep the water lively and fresh. Ensure sufficient dissolved oxygen. Feed should be placed at fixed points, at fixed times, and in fixed amounts, with as diverse a variety as possible, fed once each morning and evening, and the feed should be placed at the shallow-water edge of the pond. Crayfish have 6 major characteristics: first, they are large and plump; second, they grow quickly and have high yields; third, they are nutritious and have tender meat; fourth, they have strong adaptability and can survive in harsh weather and environments; fifth, they are omnivorous and can eat both animal feed and artificial compound feed and humus; sixth, they have high economic benefits.
In fact, whether farming crayfish or farming other aquaculture industries, there are certain risks, and farmers need to be mentally prepared to bear these before farming. It is best to fully understand some of the living habits of crayfish before farming.