A Detailed Explanation of the Latest Scientific Crayfish Farming Techniques

Because of the popularity of crayfish among the general public, some people believe that farming crayfish is highly profitable. Therefore, many farmers as well as people outside the industry are willing to farm crayfish, so the technical essentials of crayfish farming are extremely important to them.

Latest Scientific Crayfish Farming Techniques

1. Seedling rearing

The rearing pond should mainly be a cement pond with an area of 20-40 sq m and a water depth of 0.6-0.8 m; a pond close to a water source with good water quality may also be chosen, with drainage and anti-escape facilities built. Before stocking seedlings, the pond must be strictly disinfected, base fertilizer applied to cultivate plankton as the initial feed, and aquatic plants transplanted to cover 30% of the water surface. Stock 100,000-150,000 juvenile shrimp of 0.8 cm per mu; in the early stage, rely mainly on natural feed, appropriately feeding soybean milk and minced fish, and as the individuals grow, rely mainly on artificial feed.

2. Pond farming

Stock 10,000-15,000 juvenile shrimp per mu, regularly splash quicklime to increase the calcium content in the water, and increase the amount of feed fed at night, mainly using compound feed.

3. Rice field farming

Choose fields with good water quality, no surrounding pollution sources, strong water retention capacity, convenient irrigation and drainage, and no risk of flooding by floods for rice field crayfish farming. Along the inner side of the rice field ridge, dig a shrimp-raising ditch around the perimeter, 1.5 m wide and 1 m deep. For larger fields, also dig field ditches in the middle of the field, 1 m wide and 0.5 m deep. The shrimp-raising ditches and field ditches should account for about 20% of the total rice field area. The ridge surface should be more than 3 m wide and the ridge height 1 m. At 1 m from the ridge, drive a 1.5 m high stake every 3 m, set up with bamboo, and plant melons, beans, gourds, etc. along the ridge; after the vines climb the trellis, they provide shade and heat relief in the hot summer. In the shrimp-raising ditches and field, transplant aquatic plants such as eelgrass, hornwort, and coontail, which are submerged plants; the aquatic plant coverage should preferably be 30%, and it is better for them to be scattered and dispersed, which helps the water flow in the shrimp ditches stay unobstructed. Build anti-escape walls around the field with plastic film, cement boards, asbestos tiles, or calcium-plastic boards to prevent crayfish from escaping.

4. Seedling stocking

Crayfish stocking requires water testing; only after the water is safe can the shrimp be stocked.

There are two methods for stocking crayfish: First, in early September after the rice harvest, stock brood shrimp directly into the rice field to let them reproduce on their own. According to the actual conditions of rice field farming, generally stock 20 kg per mu of crayfish with individuals above 40 g each, with a female-to-male ratio of 3:1.

Second, in May after rice transplanting, stock juvenile shrimp of 2-4 cm at 1,500-2,000 per mu or 30 kg per mu. When stocking crayfish, pay attention to the quality of the juvenile shrimp; the stocking size in the same field should be as uniform as possible, and they should be stocked all at once. Stock on a clear morning or on a cloudy and rainy day, and when stocking juvenile shrimp, bathe them in 3%-4% salt water for 10 minutes for disinfection.

5. Suitable areas

Ponds, low-lying land, river channels, and rice fields can all be used for farming.

The Living Habits of Crayfish

Crayfish are omnivorous animals that mainly eat plant matter; small fish, small shrimp, plankton, benthic organisms, and algae can all serve as their food. Crayfish have weak reproductive capacity, reproducing once a year.

Crayfish have very strong survival ability. Besides Asia, Europe and Africa are also their home, so they have become a world-class delicacy. In Europe, Africa, Australia, Canada, New Zealand, and the United States, people eat them. Louisiana in the United States claims to produce 90% of the world's crayfish, and local people eat 70% of that. The worldwide “success” of crayfish, apart from some advantages in morphology and habits, is also partly due to its tolerance of polluted environments.

Morphological Characteristics of Crayfish

Body length of crayfish refers to the straight length from the base of the eyestalk to the end of the tail segment (cm); total length refers to the straight length from the tip of the rostrum to the end of the tail fan (cm). People habitually believe that crayfish seedlings generally refer to a certain product shrimp specification referring to body length. Crayfish are composed of the cephalothorax and abdomen, with 21 body segments in total and 19 pairs of appendages. The body surface has a hard carapace. The head has 5 segments and the thorax has 8 segments; the head and thorax merge into a whole, called the cephalothorax. The cephalothorax is cylindrical, with a rostrum at the front end, triangular in shape; the surface of the rostrum is smooth and flat, with a concave groove in the middle, and the front end is sharp and aggressive; there is an arc-shaped cervical groove in the middle of the cephalothorax, with rough granules on both sides.

The abdomen has 7 segments in total, and at its rear end there is a flat telson, which together with the appendages of the sixth abdominal segment forms the tail fan. There are 5 pairs of thoracic legs; the first pair is chelate and thick; the second and third pairs are pincer-like, and the last two pairs are claw-like. There are 6 pairs of abdominal legs; the first pair of abdominal legs in females is degenerated, and the first two pairs of abdominal legs in males evolve into calcareous copulatory organs; each pair of appendages has its own function. Sexually mature crayfish are dark red or deep red, while immature individuals vary from light brown, yellowish brown, to reddish brown, and blue is sometimes seen. Common crayfish individuals have a total length of 4.0-12.0 cm.

Species Hazards of Crayfish

Crayfish are farmed all over the world and form huge wild populations. China introduced them from Japan in the 1930s-1940s, and Japan had introduced the species from the United States even earlier, mainly for food and as pets. Crayfish are often co-cultured in crop fields such as rice paddies. Artificial hatching is not needed; once the original stock is put into a pond, self-maintenance can be achieved, and after harvest there is no need to stock the original stock again. Escaped individuals dig holes in embankments and survive. They can survive in temporary water bodies, have a wide diet, establish populations extremely quickly, and spread easily.

They pose a great threat to local fish, crustaceans, and aquatic plants, destroying the local food chain; because they feed on root systems, they directly cause disastrous damage to crops (especially aquatic and semi-aquatic crops such as rice) and natural vegetation; burrowing causes loss of irrigation water and damage to fields; because crayfish have a very mixed diet, they have a certain degree of impact on fish fry rearing and the cultivation of 1-year-old fish stocks, and harm artificially bred juvenile mussels.

Because crayfish have strong adaptability, strong stress resistance, a wide diet, and fast population proliferation, they often cut crops, especially rice crops, and may compete with local freshwater crayfish species.

We have always paid attention to the deliciousness of crayfish, but have never understood that crayfish are so aggressive in their living environment, which also makes survival difficult for other organisms and, in severe cases, may affect the reproduction of other aquatic organisms, thereby destroying the balance of the ecological environment and the food chain.