Crayfish (scientific name Procambarus clarkii, also known as Macrobrachium nippon) is commonly called because it is similar to the lobster in the sea.

Procambarus clarkii

Distinguishing features: it looks like a shrimp with a hard shell. The adult is about 5.6~ 1 1.9cm long, dark red, with a nearly black shell and a wedge-shaped stripe on the back of the abdomen. Young shrimps are uniform gray, sometimes with black ripples. Long and narrow claws. The middle part of the carapace is not separated by a mesh gap, and there are obvious particles on the carapace. The forehead sword has lateral spines or the end of the forehead sword is scored.

Biological characteristics: crayfish adapt to dissolved oxygen in different water bodies. The depth of its excavation is the key factor to determine the degree of its harm. Eating habits are complex and diverse. They mate from late April to July, and larvae hatch after September. The larvae are attached to the mother's abdominal swimming feet, and the growth and development process of the larvae stage is completed under the protection of the mother. This way of breeding offspring ensures a high survival rate of offspring.

Origin: Central and South America and northeastern Mexico.

Distribution status of China: It has expanded to Anhui, Shanghai, Jiangsu, Hongkong, Taiwan Province and other places, forming a large number of natural populations.

Causes and hazards of introduction and diffusion: Now there are aquaculture all over the world, and a large number of wild populations are formed. China was introduced from Japan in 1930s and 1940s, and Japan was introduced from America earlier, mainly used as food and pets. Procambarus clarkii is often mixed in crops (such as rice) fields. There is no need for artificial incubation. Once the original seed is put into the pond, it can achieve self-maintenance. After harvesting, it is not necessary to put the original seed again. Escaped individuals dug holes in the dam to survive. They can survive in temporary water bodies, and they have a wide range of feeding habits, and the speed of establishing populations is extremely fast and easy to spread. Extremely threatening local fish, crustaceans and aquatic plants, destroying the local food chain; Because it feeds on roots, it directly damages crops (especially aquatic and semi-aquatic crops such as rice) and natural vegetation; The loss of irrigation water caused by building holes and the field