Distribution and conservation status of Perforatella rubiginosa (Pulmonata: Helicidae) in Britain

In 1995 a survey was undertaken on behalf of the statutory conservation age ncy, English Nature as part of their Species Recovery Programme to determin e the status of the known populations of Perforatella rubiginosa in England and to identify other populations within the known range. The results demonstrated that P. rubiginosa was thriving at all of its know n British sites which lie in the Thames basin, except Burham, Kent where on ly dead shells were found. Many of the populations are large and are more e xtensive than previously recognized. In addition, it was also found on Bren tford Ait East, representing a new site for the species. In Britain, P. rubiginosa is demanding in its habitat requirements. Mast si tes are within the flood zone of tidal freshwater rivers and are characteri zed by having areas of bare mud vegetated by tall herbs. Flood rubbish such as planks, logs, dead stems and plastic is a feature at all sites and repr esents an important refuge for the snail. Most sites are relatively shelter ed and would be gently lapped by a significant proportion of high tides. The restricted nature and extent of the habitat at all sites means that all populations are vulnerable. The principal threats come from industrial and urban development; inhibition of the tidal action by piling, barrages or l ocks and over-management such as clearance of the flood rubbish.