Habitat point records from 1982 Lumb Menai Strait sublittoral survey

This broad-scale survey was commissioned by the NCC to determine the range and distribution of sublittoral habitats and communities within the Menai Strait and adjacent areas. The survey complements other NCC funded studies of the rocky and soft sediment shores of the Menai Strait also carried out in 1982 and follows a long history of scientific investigation in the Strait. The central region of the Menai Strait is between 250 m and 500 m wide and 3 m to 25 m deep. The seabed consists of rocky shoals with areas of stones and gravel. To the north-east the Strait widens and extensive areas of mud and sand flats occur. To the south-west there are large areas of sand banks and where the low water channel is narrow the bottom is scoured and stony. Sediment predominates on the west coast of Anglesey, and on the east coast extensive rocky substrata are present. Wave action is generally reduced within the Strait, but tidal velocities reach 8 knots in the central area, although the current is sufficiently low in other regions to allow deposition of silt. Transects were selected at 1 km intervals along the Strait for dive sites, and site profiles recorded outside the Strait. Habitats were described, algal and animal communities recorded and photographs of the range of habitat types, communities and species observed taken. A total of 40 sites were surveyed and the distribution of major habitats and communities in the survey area mapped using survey results and other published and unpublished information. The report gives full descriptions of communities present in all habitat types identified and their extent and provides notes on the distribution and habitat preferences of each species. Biogeographical discontinuities within the survey area are identified and attributed to the influence of a range of environmental factors including wave action, water quality, the distribution of rocky substrata and geology. Some typical west coast species are identified and other species found to be common on the east coast but uncommon or rare on the west coast survey area. The diversity and richness of habitats and communities in the survey area is described. Only a limited range of habitats were present at the west coast sites surveyed, this part of the survey area being atypical of the west coast of Anglesey as a whole due to the increased turbidity conditions. Greater diversity is found further to the north-west of the survey area on this coast. The east coast sites showed a considerable diversity of habitats due to the broken limestone substratum and the variation in exposure to tidal streams in the vicinity of Puffin Island. The varied local topography and geology of the Menai Strait produced a series of habitats ranging in tidal stream exposure from very exposed to sheltered. The faunal communities recorded and the habitats in which they were observed could be distinctly identified, each often dominating areas of seabed although ultimately forming part of a continuum. As a tidal rapid, the habitats present in the central region of the Menai Strait are relatively unique. Although there are a number of tidal rapids on the west coast of Scotland, these are generally shallow and kelp-dominated. (The depth distribution of algae in the survey area is very restricted by the turbidity of the water and the communities present are therefore animal-dominated). The only site in the British Isles identified as having great similarity with the Menai Strait is Strangford Lough on the eastern Irish Sea coast, another example of a deep-water tidal rapids. The scientific interest and conservation value of the survey area is assessed in the report using the NCR criteria with modifications as stated in the NCC/NERC report - Nature Conservation in the Marine Environment, 1979. The survey report concludes that the designation of the central region of the Menai Strait, on its own or as part of a marine reserve encompassing the whole of the Menai Strait, would allow the conservation and maintenance of a unique ecosystem, as well as promoting survey and research programmes into the area and enhancing its educational and amenity value.

Organization: Joint Nature Conservation Committee