Efficient Crayfish Farming Techniques in Low-lying Fields

There are many people farming crayfish on the market, but some achieve high crayfish yields while others get low yields, and there are reasons for this. Farming crayfish also requires certain techniques and methods, so before raising crayfish it is very necessary to first understand some techniques and methods.

Efficient Crayfish Farming Techniques in Low-lying Fields

1. Pond conditions and preparation before stocking. Choose a low-lying area along the embankment within the polder, with sandy loam as the bottom soil, and an area of 0.5 hectares. The water flow is relatively stable, and after raising and reinforcing the pond embankment, the effective water storage is 1.2 m. The inlet and outlet are separate.

Before releasing the shrimp fry, clear the wild weeds in the pond, dry the pond and expose it to the sun for 2 weeks, then sprinkle lump lime mixed with water, using 150 kg per 667 sq m, to kill wild fish, pathogens, and so on in the pond. After clearing the wild weeds, manually transplant excellent aquatic plants, such as water peanut, Elodea, and hornwort; these aquatic plants have strong regenerative capacity and are very suitable for crayfish to live and inhabit. The escape ability of crayfish is no less than that of river crabs. Under artificial farming conditions, when the living environment is poor, they are extremely likely to escape. Use calcium-plastic boards on the embankment, bury plastic colored strip cloth in the middle of the embankment, and tightly fasten the inlet and outlet with fine-mesh nets to prevent escape. At the same time, regularly check the anti-escape facilities. One week before releasing the shrimp fry, fertilize the water with thoroughly decomposed manure, in the same way as fertilizing water before fish fry are put into the pond, so that the shrimp fry have abundant food when they enter the pond. The first addition of new water should not be too deep; about 50 cm is appropriate. As the shrimp fry grow, water can be added gradually. 2. Fry stocking. Every year in March, purchase fresh live shrimp fry from the market and surrounding ponds. On March 5, release 10 kg of 2.5 cm shrimp fry; on March 10, release 15 kg of 3 cm shrimp fry; on March 15, release 222 kg of 3.5 cm shrimp fry; on March 18, release 365 kg of shrimp fry larger than 4 cm. Because the shrimp fry are transported nearby, before entering the pond, remove dead fry and soft-shelled shrimp fry, then disinfect with 40 g/L salt water for 10 minutes to kill surface bacteria and parasites. 3. Feeding management. Start baiting in mid-March. In the early stage, mainly feed fresh bean dregs and rice bran. From May to September, feed ice-fresh fish, pumpkin, green vegetable leaves, and so on. Ensure the crayfish eat enough and eat well. The feeding amount is 5-10% of body weight, specifically controlled flexibly according to the crayfish's feeding and activity conditions. Ice-fresh fish should be chopped into small pieces for feeding, and pumpkin should be cut into shreds to facilitate ingestion by the crayfish. Residual bait should be removed promptly to prevent deterioration of water quality.

The water quality for raising crayfish should be “fertile, lively, tender, and refreshing.” In the early stage, it should be fertile, with water color mainly yellow-green and tea-brown, and transparency around 30 cm. If transparency is too low, increase the amount of water added, and change the water once every half month. In summer, keep transparency at around 40 cm. Keep the water level at 1.2 m, aquatic plant coverage at 50%, and pH controlled at 7.5-8. Disease prevention and control should focus on prevention, with regular water changes. Throughout the entire farming process, sprinkle quicklime 2 times, and feed garlic heads 6 times in summer; no obvious diseases occurred. During the farming period, insist on patrolling the pond daily, observing the crayfish's feeding, activity, and growth, as well as the inlet and outlet and anti-escape facilities, and deal with problems promptly when found. Crayfish have an extremely strong burrowing ability, so be sure to patrol the outer side of the pond embankment. 4. Discussion of results. Begin harvesting commercial shrimp from late May, with a size of 20-25 shrimp per kg. Harvest the large ones and leave the small ones. The harvesting method is ground cage harvesting, taking shrimp once every 4-8 hours to prevent crayfish from dying densely in the ground cages or damaging the harvesting tools with their claws. A total of 1830 kg was harvested, with a size of 20-25 shrimp per kg, an average price of 16 yuan/kg, a total output value of 29,280 yuan, a total cost of 19,530 yuan, and a profit of 9,750 yuan. Crayfish have extremely strong adaptability to life. In the wild state, they live and die on their own, and yields are very unstable. Under artificial high-density farming conditions, crayfish become very fragile, and 3 points must be noted: (1) Insist on pond patrols; crayfish have strong burrowing ability and strong climbing ability on land, so preventing escape is key; (2) Crayfish grow quickly and kill each other regardless of size, so during artificial farming they should be raised by size class; (3) Harvest the large ones and leave the small ones, which can improve farming efficiency.  

Crayfish Farming Cycle  

The key depends on water temperature. The reproductive period of crayfish is somewhat different from that of ordinary animals. Most ordinary animals reproduce in spring, while crayfish mostly reproduce in autumn. The fry must go through one winter to summer before they can grow to maturity, because in winter the water temperature is low, and the fry grow slowly or even do not grow. If the water temperature is suitable and nutrition is rich, crayfish can grow to maturity in only 50-70 days.  

It also depends on the situation. If wild, because they reproduce very quickly, release shrimp in March-April, directly releasing large shrimp to let them reproduce freely, and they can be caught around June, after which they can be caught every day.  

Artificially bred varieties grow faster. The “Huafeng No. 9” variety from the Wuhan Huayufeng Aquatic Products Farm can grow to the marketable size of 50-70 g in a growth cycle of 60-90 days.

How to Clean Crayfish  

1. Put the crayfish directly into clean water mixed with vinegar and salt, soak for 30 minutes to force the crayfish to spit out the dirt in the gills, and use a small brush to carefully scrub every part of the crayfish's body one by one.  

2. Peel off the crayfish's head shell, and we can see the stomach sac that serves as a digestive organ. It is very dirty, and this must be removed. There is something like an intestine on the crayfish's abdomen, and it must also be removed! Just pinch the middle flap of the crayfish's tail and pull it out, and it can be easily done.  

3. There is delicious ‘roe’ in the crayfish's head shell, so when cleaning again, use scissors to cut from the top of the head diagonally downward at about a 45-degree angle, so that the stomach sac can be taken out while preserving the ‘roe.’ Finally, remember to rinse carefully with a thin stream of water.  

4. Put the crayfish in a pot and boil in boiling water; the white dirty foam will slowly come out. Skim off the foam with a spoon, and the crayfish are clean.

Crayfish Farming Costs  

Broadly speaking, the cost of raising crayfish is only 2 yuan per kg. If raised at home, the average cost per kg reaches 3 yuan. Crayfish are sold by size: one about 75 g sells for 3 yuan, one about 50 g for 1.5 yuan, one about 40 g for 1 yuan, and those below 40 g are kept in the pond for continued raising. “On average, one sold for 1.6 yuan.  

The stocking density of fry depends on fry size, shrimp pond area, pond water depth, pond bottom conditions, water exchange conditions, bait type, rearing method, production skills, and management level. It should also be determined by referring to the yield requirements and size indicators proposed by the shrimp farmer. The amount of fry to stock can be calculated by referring to the following formula:  

Fry stocking amount = (planned fry yield (kg) × number of shrimp required to produce 1 kg) / estimated survival rate  

In the formula: the planned yield per mu can refer to the yields of neighboring areas in past years; the number of shrimp required to produce 1 kg of shrimp can be calculated as 30-50 shrimp (body length 12-15 cm); the survival rate is calculated as 50%-70%, and for intermediate-cultured shrimp fry as 85%.  

Generally, for intensive shrimp ponds, under conditions of good fry quality, superior water exchange conditions, guaranteed bait, and high rearing management level, the stocking amount per mu can be about 20,000 fry (not more than 25,000 fry). For shrimp fry that have undergone intermediate culture (body length about 2.5 cm), the stocking amount per mu should be controlled between 8,000-12,000 fry.

The current market for crayfish is increasingly tight, and more and more people like to eat crayfish. Therefore, there are also many people farming crayfish on the market, but beginners in crayfish farming should learn more from successful people and share successful experience together.