Crayfish has a very strong viability. Besides Japan and China, Europe and Africa also occupy its territory, so it has become a world-class invasive species and a world-class delicacy. In Europe, Africa, Australia, Canada, New Zealand and the United States, people eat crayfish. Louisiana in the United States claims to produce 90% of the world's crayfish, and local people eat 70% of them. ?
The "success" of crayfish in the world is partly attributed to its tolerance to polluted environment, except for some advantages in morphology and habits. In scientific research, organisms that are very sensitive to pollutants or very tolerant are often used as indicators of whether the environment is polluted or not. Crayfish is such a potential indicator. ?
Crayfish are native to saprophagous, Louisiana in the south of the United States, and entered China in the early 20th century with the biological invasion of foreign cargo ships such as ballast water. The so-called creature used by the Japanese to clean up the bodies is untrue. On the other hand, at that time, the Japanese raised crayfish as bait for bullfrog breeding (however, some data show that it was brought into Shandong area of China by the Japanese in the late 1930s. See China Biological Invasion Research Science Press Wan Fanghao, Guo Jianying, etc.).
Because natural enemies have not been formed in China, after decades of diffusion, the most common freshwater economic shrimps have been formed in China, which are widely distributed in Shandong and provinces and cities in the middle and lower reaches of the Yangtze River.