The North American signal crayfish,Pacifastacus leniusculus (Dana), established in the wild in Scotland

1. Although the North American signal crayfish, Pacifastacus leniusculus (Dana), has been brought into Scotland for aquaculture several times in the past, there appears to be no record of it ever having become established in the wild here. 2. The species is now recorded as being well established at a stream site in south-west Scotland where many specimens were collected in the summer of 1995. Local information indicates that the species has occurred there for several years. 3. The significance of this record is that Scotland is no longer free from this aggressive and invasive species. Fortunately, this locality is far away from the only population of the native white-clawed crayfish Austropotamobius pallipes (Lereboullet), an introduced stock which has been long established in north-west Scotland.