Habitat point records from 1984 NCC/OPRU Loch Sween sublittoral survey

Loch Sween is situated on the east side of the Sound of Jura, in south-west Scotland. It opens to the south-west and its mouth is partially protected by the small MacCormaig Isles. The main body of the loch is relatively straight, with a fringe of rocks or gravel giving way to a sandy or muddy seabed. There are a number of 'arms' to the loch which add considerably to the diverstiy of habitats present. Linne Mhuirich forms an arm to the west, with a constricted mouth into Loch Sween forming an area of tidal rapids. At the head of the loch, arms include the silled Caol Scotnish. Loch Sween has been proposed as a Marine Nature Reserve by NCC on account of the high scientific interest and conservation importance of habitats and communities within the loch. Already a site of historical marine biological recording and research, NCC commisioned extensive systematic littoral and sublittoral surveys in 1982 (Smith, 1982; Earll, 1982, 1984). Further information was required on the distribution and types of littoral and sublittoral habitats and communities present, to assess the relative importances of individual areas and the integrated importance of the whole loch. Information was needed to assess management requirements, particularly where fragile communities might be exposed to enviromental impacts from mariculture activities within the loch. The 1984 survey work had the following objectives: - to describe the littoral communities: reported in Rostron and Hiscock (1985) - to moniter the enviromental impact of fish and shell fish farming in the loch: for incorporation into general fish farming assessments. - to further investigate sublittoral habitats and communities: covered in this report. Surveys were undertaken of the sills at the entrance to Linne Mhuirich and Caol Scotnish. The composition and distribution of the habitats and communities at these sites, respectively Linne Mhuirich Rapids and Caol Scotnish Narrows, are described in the report. Similar comparative studies were carried out in these two arms of the loch, looking primarily at the epibenthic sediment communities. An additional investigation of circalittoral bedrock communities in the main loch was made. The results emphasise the scientific interest of the individual areas. The differences observed between sill and sub-loch systems are significant and inclusion of the variants is shown to enhance rather than duplicate the range of habitats and community types present. No seperate assessment of scientific interest and conservation importance is made in this report. Records currently considered sensitive have been removed from this dataset.