Fig. 2

Distribution of Crepidula fornicata in the Milford Haven Waterway, its northern-most geographical location in Wales, UK. Each marker represents the start coordinates of a transect that was surveyed during the surveys of 2009 and 2010. Intertidal densities of C. fornicata were estimated at 10 sites (orange markers and place labels) from 10 1-m² quadrats per surveyed ~100 m transect (1.0–1.3 m above C.D.). Subtidal densities (red markers) are averages of counts from 30 still images, each covering ~0.13 m² of the seabed, taken along ~150–210 m transects using an underwater camera mounted on a vessel-towed sled. Bright and dark green markers are stations where no C. fornicata were found subtidally or intertidally, respectively (colour figure online)