Distribution of crayfish in Europe and some adjoining countries.

The distribution of crayfish in Europe is examined using information from a variety of sources mainly for the last two decades. All European countries have at least one indigenous crayfish species (ICS), many with large stocks, and most countries in Western Europe have at least one non-indigenous crayfish species (NICS). Some species termed indigenous in certain countries may have been introduced in relatively recent times. However, the meaning of the term indigenous (native) varies between countries. NICS continue to expand their ranges and present a continued threat to ICS through competition and transmission of diseases, notably crayfish plague. The current high level of interest in crayfish means that many countries are monitoring their crayfish situation and, where necessary, taking steps to renew stocks of threatened indigenous species, some of which are apparently on the verge of extinction. A more regular monitoring programme for European crayfish as a whole is needed if the demise of indigenous species is to be prevented.