ABSTRACT
The species has been widely introduced throughout Europe, as well as to Japan and other parts of North America, and is the most widespread of any introduced crayfish species (Holdich et al, 2009). It was largely introduced for aquaculture, as it is a large, fecund and fast growing species that can reach high densities (Hiley, 2002), but has also been introduced for the aquarium trade, fish markets and probably by anglers as supplemental food for fish stocks (Peay et al, 2010). On occasion, signal crayfish have also been introduced for weed clearance (Rogers and Loveridge, 2000; Howells and Slater, 2004) or discarded as unused bait or even as unwanted aquarium pets (Holdich et al, 2009). They may well have also been accidentally introduced through transport in association with fish, a common mode of unintentional invertebrate introductions (Gherardi et al, 2008). They are still sold live in fish markets for human consumption, providing continuing opportunities for the species to expand its range through further escapes into the wild (Holdich and Sibley, 2009).
