Rapid assessment of marine non-native species in northern Scotland and a synthesis of existing Scottish records

In this study, we compiled existing records of fouling marine non-native species in Scotland, and created a national checklist of these species. We then targeted a selection of these species (excluding those that could not be reliably identified) in a rapid assessment survey of 27 harbours in the north of Scotland. Collation of existing records revealed that 23 fouling marine non-native species were known to be present in Scotland. The geographic distribution of these records was not uniform, and they were largely underrepresented in the north and east of mainland Scotland, likely as result of lack of survey effort. In the rapid assessment survey of north Scotland, 9 out of 18 targeted species were found: Austrominius modestus (Darwin, 1854); Botrylloides violaceus Oka, 1927; Caprella mutica Schurin, 1935; Codium fragile fragile (Suringar) Hariot, 1889; Corella eumyota Traustedt, 1882; Heterosiphonia japonica Yendo, 1920; Neosiphonia harveyi (Bailey) Kim, Choi, Guiry and Saunders, 2001; Schizoporella japonica Ortmann, 1890; and Tricellaria inopinata d'Hondt and Occhipinti Ambrogi, 1985. The non-native bryozoan Bugula simplex Hincks, 1886, which was not targeted, was also found, and this constituted the first confirmed Scottish record. The surveys provided 60 new records and extended the northward national range for most of the species found. The number of fouling non-native species in the surveyed harbours was positively associated with the presence of floating structures and vessel activity indices. Our study presents an overview of the current status of fouling marine non-native species in Scotland, and the results of the first comprehensive survey of these species in the north of Scotland. The latter provides a baseline dataset for monitoring future changes, which may occur as a result of the development of the wave and tidal energy industry in the north of Scotland. The wave and tidal energy industry has the potential to facilitate the invasion of fouling marine non-native species through the provision of habitat and by increasing vector activity.