Habitat point records from 1989 UMBSM Arisaig and Moidart sealochs survey

Five sealochs to the north-east of the Ardnamurchan Peninsula were surveyed during 1989 as part of the survey of the Scottish sealochs. All of the lochs were markedly different in character. Loch Ailort, which is 8km long and has 3 shallow sills, is 43m in the basin at its head, has a wide range of exposures and a narrow with strong tidal streams. Loch nan Uamh, with a maximum depth of 52m, is wide and open to the south-west and so has few sheltered areas. Loch nan Ceall is shallow, has a narrow entrance channel with strong tidal streams and a group of skerries with coarse sediment shores across its entrance. Loch Ceann Traigh is open to the north and reaches a maximum depth of 44m with a shallow shelf and channel connecting it to Kentra Bay. This and Loch Moidart, which has considerable freshwater input, have extensive areas of littoral sediments; Loch Moidart also has a deep, sheltered arm, the North Channel, which is separated from the rest of the loch by an intertidal bar. Thus the area as a whole has a full exposure gradient, several narrows systems and extensive areas of littoral sediments which are unusual in Scotland, but a limited range of sublittoral hard substrata. There have been fish farming operations in the area since 1967. The Sea Fish Industry Authority has a laboratory in Loch Ceann Traigh and Marine Harvest Ltd. have a large salmon farm and hatchery in Loch Ailort. There are several SSSIs in the area; these include the mud and sand flats of Kentra Bay and Loch Moidart. A considerable amount of littoral survey work has been carried out in the area, most notably by Lewis (1957), Smith (1978) and Powell et al. (1980). Eighty-four sites were surveyed of which 16 were littoral and 68 were sublittoral, including 5 dredge sites; 34 community types were described. Sheltered bedrock communities were found in Loch Ailort, Loch Moidart and parts of Loch nan Uamh, with fucoid dominated shores giving way to Laminaria saccharina in the infralittoral. Protanthea simplex characterized the circalittoral in Loch Ailort whilst an unusual community dominated by Bispira volutacornis and ascidians was found in the North Channel, Loch Moidart. More exposed bedrock had barnacle dominated shores and a mixed Laminaria hyperborea/L.saccharina kelp forest with heavily grazed circalittoral communities. Tide swept bedrock was common in the channels with rich communities dominated by filter feeders. Sediment communities were more varied. Beds of Arenicola marina and littoral estuarine sediments were found in Loch Moidart, and particularly rich maerl gravel shores in Loch nan Ceall and Loch Ailort. In the sublittoral, extensive beds of maerl Phymatolithon calcareum supporting a very diverse community were found in Lochs Ailort and nan Ceall; these may prove to be the best examples in Scotland. Some small areas of Zostera marina were also found. Muddy gravel communities were widely distributed and in more exposed situations, there were large areas of coarse, clean sand and gravel, characterized by the holothurian Neopentadactyla mixta. Deep mud communities were poorly represented although Brissopsis lyrifera, Amphiura spp. and Nephrops norvegicus were found in Loch nan Uamh and the entrance to Loch Ailort. Shallow mud in Loch nan Ceall supported Philine aperta and the very rare holothurian Labidoplax media whilst mud in Loch Ailort was barren with bacterial patches. The sealochs of Arisaig and Moidart, taken as a whole, have and unusual balance of communities when compared to other areas although many of the individual communities are widely distributed in the west of Scotland. Of particular note are the maerl gravel shores and the sublittoral maerl beds. Fifteen communities and 20 species have been provisionally assessed to be of Regional or National conservation importance. Records currently considered sensitive have been removed from this dataset.

Organization: Joint Nature Conservation Committee