Signal crayfish

The signal crayfish, Pacifastacus leniusculus, is an American crayfish indigenous to the western US. Due to the crayfish plague that ravaged European crayfish stocks and has almost exterminated the noble crayfish Astacus astacus, Swedish biologists searched for a crayfish that could replace the native European crayfish. They found the signal crayfish and started to introduce it into Swedish rivers and lakes. This was the beginning of the introduction of this crayfish not only to various European countries but also to Japan.

Unfortunately, this crayfish has been carelessly introduced to various countries without considering the fact that it carries the crayfish plague, and thus causes the eventual extermination of native crayfish. This was the case both in Great Britain and in Japan.