Foreigners don't eat crayfish because they think crayfish are attached with toxic substances.

crayfish (scientific name: Procambarus clarkii): also known as Procambarus clarkii, red crayfish and freshwater crayfish. Shaped like a shrimp with a hard shell. The adult is about 5.6~11.9 cm long, dark red, with a nearly black carapace 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.

is a freshwater economic shrimp, which is widely welcomed by people because of its delicious meat. Because of its omnivorousness, fast growth and strong adaptability, it has formed an absolute competitive advantage in the local ecological environment. Its feeding range includes aquatic plants, algae, aquatic insects, animal carcasses, etc. When food is scarce, it also kills each other. Crayfish has become an important economic breed in China in recent years. In the process of commercial farming, we should guard against escape, especially into the untouched original ecological water body. Its ecological competitive advantage on local species leads to destructive harm

Crayfish has been eaten in the United States for hundreds of years, and the sale of crayfish has gradually moved from country fairs to large-scale transactions. Crayfish is a very common cooking ingredient in the United States. It is usually boiled with potato and corn and seasoned with kajiang powder. 98% of crayfish used for food in the United States are produced in Louisiana. In 1983, Louisiana even selected crayfish as the state representative animal, and held the "Crawfish Festival" every year.

It is rumored that although heavy metals and oil stains are not the feeding objects of crayfish, these "toxic" substances can attach to the food and enter the lobster, and the "toxic substances" in the lobster will not be excreted, but will only accumulate gradually, so the heavy metals in the crayfish will exceed the standard in a seriously polluted environment.

Crayfish can survive in heavily polluted places, but most of the heavy metals it ingests are transferred to the shell. With the continuous growth and shelling, these heavy metal toxins are removed from the body, so the heavy metals in the meat may not exceed the standard. The research data show that most of the heavy metals in crayfish are concentrated in the head except the shell, and there is not much heavy metal in the tail we eat, which is unlikely to cause poisoning.