No abstract

The global decline of freshwater bivalves (Unionida) has prompted many programmes for their conservation and augmentation, which often include a captive breeding component. One key point to such programmes is the collection, maintenance and use of mussel glochidium larvae, which require attachment to a fish host in a sensitive parasitic stage of their life cycle. Understanding the thermal limits of glochidia can increase knowledge of mussel larval survival and ultimately aid in the development of conservation programmes. Glochidia of the endangered thick-shelled river mussel Unio crassus and the non-native Chinese pond mussel Sinanodonta woodiana were observed for active clamping ability at 5, 15, 17, 20 and 25 °C over the course of a 7-d period. The results from this study confirm that an inverse relationship between water temperature and larval viability can be observed in both species. Additionally, the significantly higher thermal tolerance of S. woodiana indicates that the species exhibits competitive invasive behaviour beginning from the larval stage. These findings also suggest that the collection and transportation of glochidia from genetically important yet distant populations is feasible if the larvae can be maintained at temperatures between 5 and 15 °C.

Freshwater bivalves are key faunal elements of aquatic ecosystems. Native species declines are paralleled by increasing distribution and abundances of non-native species. Appropriate management of both groups depends on knowledge of their interactions, which remains limited. Herein, we systematically review the current knowledge status of native and non-native bivalves in Europe, analyzing their functional interactions as well as niche and distribution overlaps between species. We also review existing management tools for non-native species in light of their applicability and sustainability. Strong and multiple interactions as well as niche overlaps between native and non-native bivalves already exist in Central Europe, especially with regard to Dreissena spp., Corbicula spp., and Sinanodonta woodiana. Direct competition is low with native species that have a high degree of specialization such as Margaritifera margaritifera, whereas the greatest niche overlap and competition occurs in generalist species such as Anadonta anatina, Unio pictorum, and S. woodiana. Early detection and preventive measures against undesired species are most successful in limiting their spread. Most methods for managing non-native species are unspecific and thus also include undesired side effects on endangered native species. The conservation and restoration of functionally intact bivalve habitats are the most sustainable and most resilient ways of management.