The sale of crayfish in the pet trade has increased in recent decades, and a substantial fraction of the world's entire range of crayfish species is available in the pet trade. The market for pet crayfish creates two major concerns: the potential for over exploitation of natural populations of crayfish to supply the pet trade, and the negative consequences resulting from the release of non-indigenous crayfish into natural habitats. The chain from the source of crayfish to the final owner can be lengthy, and each step in the supply chain needs to be studied by different methods. While there are often regulations intended to limit the trade of crayfish as pets, they differ widely from place to place and seem to have limited success in changing the behaviour of owners of pet crayfish.