Distribution of the introduced amphipod, Caprella mutica Schurin, 1935, on the west coast of Scotland and a review of its global distribution.

Caprella mutica Schurin, 1935 was first described from sub-boreal areas of north-east Asia. In less than 40 years C. mutica has spread throughout the northern hemisphere and the first recorded sighting in the southern hemisphere is reported here. Caprella mutica has been introduced to temperate oceanic coasts between latitudes of 25 and 70 degrees N. Outside its native range, C. mutica has only been found in areas of human activity, including ports, aquaculture facilities and an oilrig; the species has not yet been found in natural habitats. Shipping and aquaculture transfers are the most likely long distance vectors; recreational boating and drifting weed are the most likely short distance vectors. Temperature and salinity do not explain the small-scale distribution of C. mutica on the west coast of Scotland; globally its annual temperature range is 0-22 degrees C. This suggests that the local scale distribution of C. mutica is potentially limited by the availability of suitable transportation vectors during the dispersal phase rather than by physical environmental factors following release.