Integrative Conservation Biology of European Freshwater Mussels: the Importance of Fish Hosts, Stream Substratum Properties and Population Genetics

Unionid freshwater mussels are considered the most endangered group of all freshwater organisms. They have a complex life cycle which includes a parasitic phase on a host fish as well as a post-parasitic phase during which the juveniles depend on interstitial stream substratum properties. This contribution highlights the importance of integrative approaches to identifying the critical bottlenecks in the mussel life cycle in order to deduce sound conservation management strategies. The example of the critically endangered European freshwater pearl mussel (Margaritifera margaritifera) which has a lifespan over 100 years and which has lacked recruitment in the majority of its populations for 30-50 years, illustrates how careful management of fish host populations, stream substratum properties and genetic diversity and differentiation need to be integrated for sustainable conservation. Data on European populations of the species indicate that the stream bed properties are likely to be currently the most limiting factor for survival since this habitat has been strongly altered by landuse changes and stream corrections. Evaluations of stream bed restoration measures revealed that the primary concern of restoration should be catchment erosion management. To prevent genetically unique populations from extinction, artificial culturing of such valuable populations can be an emergency measure.