Species point records from 1984 Smith Loch Sween mollusc and polychaete littoral survey

Loch Sween is one of 7 sites currently proposed by the Nature Conservancy Council as Marine Nature Reserves. It has been selected on the basis of its high scientific interest and conservation value. The present study forms part of a series of studies by or for NCC to provide more detail on the scientific interest and to provide information essential for designation and subsequent management. In addition to this study, a number of other studies were carried out in 1984, including work on the littoral habitats, communities and species described in Rostron & Hiscock (1985). Loch Sween is a sea loch some 20 km in length on the east side of the Sound of Jura. Although facing south-westwards its mouth is partly sheltered by a number of islands. The main body of the loch is linear and relatively uniform but there are several main off-shoots or 'arms' to the loch which add considerably to the habitat diversity. The objectives of this survey included surveying a number of sites not previously visited, to describe their mollusc and polychaete communities in particular as well as revisiting old sites to look at annual variation in community structure. Seasonal and longer term variations were investigated using the mollusc samples obtained from the washing of Fucus serratus. Considerable changes in community composition between years were found, often contradictory in trend. The implications of major meteorological variations between years is disclosed although no firm conclusions can be drawn. Although not mentioned in this report, the effects of FW ponding, which occurs extensively during periods of prolonged and heavy rainfall, may also contribute to the annual variation. In addition to these variations, major changes were noted between years for local community dominants such as Ascidiella aspersa and Ophiocomina nigra. A moderate range of communities was recorded, the habitat diversity being less than that found at sites outwith sea lochs investigated elsewhere on the west coast of Scotland. This would be expected and results from the reduced habitat diversity and water exchange and the increase in variability in water 'quality' found in sea lochs. Areas of increased habitat, community and species diversity were associated with shores at the entrance to several of the arms of Loch Sween where water movement was locally enhanced. Records currently considered sensitive have been removed from this dataset.