THE LOSS OF A FRESH-WATER PEARL MUSSEL (MARGARITIFERA-MARGARITIFERA) POPULATION IN NW WALES

During a recent land drainage scheme, a population of the Freshwater P earl Mussel Margaritifera margaritifera (L., 1758) was discovered in a small stream in north-west Wales. The dredging operations effectively destroyed the population which was estimated to have been as high as 5000 individuals. The presence of juvenile shells under 20 mm in the s poil tips suggests this was a viable, recruiting population. An attemp t to translocate the remaining mussels to an unaffected downstream sit e was unsuccessful. The loss of this nationally important population d emonstrates the urgent need for comprehensive distributional data upon which an effective conservation policy can be based.