Habitat point records from 1988 UMBSM Harris and Lewis sealochs survey

The sea lochs of north Harris and southern Lewis in the Outer Hebrides are amongst the most remote in the British Isles with limited, or no, road access. Six lochs were visited during the present survey, 3 on the east coast - Seaforth, Bhrollum and Claidh - and 3 on the west, Resort, Tealasavay and Tamanavay. Loch Seaforth is the largest of these, being 59 km in length with a maximum depth of 98 m. It is classed in the 'Fiordic C' category of Milne (1972). Lochs Claidh and Tamanavay, which are smaller and each have a single entrance sill, are also fiordic, and Lochs Resort, Bhrollum and Tealasavay are estuarine in character. The lochs are mostly steep sided, and there is little intertidal area. Bedrock and boulders are found in the littoral at the heads of all the lochs surveyed and occur sublittorally everywhere except in Upper Loch Seaforth. The sediments show a graduation associated with water movement with coarser sediments at the entrances to the lochs being replaced by soft mud in deeper water and very sheltered conditions. Accelerated tidal streams at the Narrows in Loch Seaforth result in coarser sediments in this area and the presence of a bed of maerl, Lithothamnion glaciale. The lochs all lie in areas with little or no habitations and there is no shore based industry. There are some salmon cages and mussel rafts in Lochs Seaforth, Claidh and Tamanavay and some creeling takes place in Lochs Seaforth and Claidh for lobsters and Norway lobsters. Scallops are taken in Loch Seaforth by trawling and diving. The southern shore of Loch Resort forms the northern boundary of the north Harris SSSI and all the lochs concerned lie within a National Scenic Area. Loch Seaforth has been proposed as a Marine Consultation Area on the basis of the present survey. Very little marine biological work has been carried out in the lochs in the past, this being limited to some littoral algal collections and surveys of fucoid and laminarian biomass in Loch Seaforth. The present survey, carried out in July and August 1988, aimed to describe the marine habitats and communities present in the lochs and assess their nature conservation importance. A total of 9 littoral and 77 sublittoral sites were visited, the latter being surveyed by diving. At each site the abundance of the epiflora and fauna was recorded and the habitats were described. No infaunal sampling was carried out. Three littoral and 29 sublittoral habitat types were identified and these and their associated communities are described in this report. A list of the taxa recorded is also given. A wide range of habitats and communities was found in Loch Seaforth with a good progression from shallow to deep and exposed to sheltered conditions and including areas of strong tidal flow. Several of the communities and species in the loch are unusual in the Western Isles. Similar communities, although on a smaller scale, were found in Loch Claidh. Loch Bhrollum has more open coast affinities as does Loch Tealasavay. Soft sediment communities in Lochs Resort and Tamanavay are very different from those on the east coast and coarser sediments were found in the Braigh Mor. Several differences were noted in the species complement of similar east and west coast communities. The scientific interest and conservation importance of the area have been assessed using standard criteria. These have been applied to each of the habitats or community types identified which have been provisionally graded as of local, regional, national or international importance. A large number of species of particular scientific and conservation interest were found. These have been tabulated and their provisional conservation importance graded as regional, national or international. Fiordic lochs are unusual in the Western Isles and thus Loch Seaforth, with its large size and range of communities, is of particular interest. All the lochs concerned, but particularly those on the west coast, are very undisturbed due to the remoteness of the region and must rank amongst the least disturbed marine habitats remaining in the British Isles. The full conservation significance of communities in the lochs will only be adequately assessed when surveys of other Scottish lochs are further advanced. Records currently considered sensitive have been removed from this dataset.

Organization: Joint Nature Conservation Committee