Wider riparian buffer strips: A cost-effective conservation measure for freshwater pearl mussels in Ireland?

Abstract

The freshwater pearl mussel Margaritifera margaritifera (FPM) is a long-lived invertebrate that is found in coarse sand or fine gravel in clean, well-oxygenated, fast-flowing and unpolluted freshwater (Moorkens 1999; 2000; Skinner et al. 2003). The species has undergone a dramatic decline in the sizes of most meta-populations and in the size of its range over the twentieth century (Young 1991; Reid et al. 2012), with an estimated reduction of over 90% in the FPM population in central Europe over this time (Bauer 1988). The species is in very serious decline throughout its range and is listed in the IUCN red data book as endangered worldwide (Baillie and Groombridge 1996) and in the most recent IUCN Irish Red List of non-marine molluscs as critically endangered (Byrne et al. 2009). Ireland is considered a stronghold for the FPM and is believed to support approximately 46% of FPM individuals in the EU (DAFF 2008). However, the NPWS (2008; 2013) concluded that recruitment levels were insufficient in all Irish FPM populations, resulting in all FPM populations, including the populations in designated Special Areas of Conservation (SAC), having unfavourable conservation status.