Species point records from 1977-82 Smith Lewis & Harris littoral mollusc survey

The area covered in this report consists of a coastline which is very deeply dissected by many sea lochs. Three subdivisions are made within the area on the basis of typography. The northernmost of these extends from Loch Grimshader to Loch Shell, and includes the complex at Lochs (Loch Grimshader, Loch Leurbost and Loch Erisort) and Loch Cuirn. All of these lochs are shallow with many islands, contrasting with the deep trench of Loch Seaforth which comprises the second area and was not studied in the investigation. The third sector covers South Harris, which has a very indented coast and numerous offshore rocks and islands. There is little tidal current over the area as a whole, although local current areas and rapids are numerous. The geology and geomorphology of the area (Lewisian Gneiss) is similar to that elsewhere in the Hebrides and north-west Scotland, as are the characteristic brackish lochs and their associated fauna. A general survey was made of the shore at the sites visited, detailed data being obtained for the Mollusca, and notes on larger members of other phyla given together with descriptions of stations. Samples of algae were taken at random for analysis of the molluscan populations thereon, thus providing a reasonably objective assessment of their size and diversity, this being extremely helpful in determination of the quality of a shore. The northerly stations showed the greater diversity, confirming the general impression gained in the field that the northern part of the Lochs - Leverburgh area was the more diverse and productive. However, compared with other parts of west Scotland, this region as whole is average. The lochs area was the main part of the coast which was found to stand out as being of particular biological merit, with good examples of a diverse range of habitat types and some interesting species present. The coast from Aird Raerinish to Loch Mharabhig was therefore, on a basis of shore survey alone, assessed as Grade 2. However, concern was noted over the pressures from development in Loch Leurbost, from fisheries (a decline in the populations of Pecten maximus and Ostrea edulis having occurred) and from overdigging of some rich shore sites in Loch Erisort. Although only one station was visited in Loch Shell, the typography indicates that this area may be as rich and nearly as interesting as Loch Erisort, (although having fewer habitat types) and being inaccessible was unlikely ever to be under pressure. It was assessed as Grade 3. Although the coast of South Harris was generally disappointing, the two sites investigated at Manish were assessed as Grade 2, being unique in Lewis and Harris, with a wide range of habitats including rich tidal rapids. These sites were under pressure from the local community. Other interesting sites include the harbour and islands at Rodel, which were assessed as Grade 3 and found to be under threat, and the Eileanan Diraclett station assessed as Grade 4. The Leverburgh waterfall, previously assessed as Grade 3 by Powell, was downgraded. At Lingarabay quarrying and building of a harbour and pier is planned. This site was found to be average or poor, and it was felt that no objections to development should be made. Records currently considered sensitive have been removed from this dataset.