Channels and ditches as the last shelter for freshwater mussels: the case of Margaritifera auricularia and other naiads inhabiting the mid Ebro River Basin, Spain

1. Freshwater mussels or naiads are generally considered to thrive in river habitats, provided the ecological conditions are good. The presence of populations of these bivalves in artificial channels and ditches with natural bottoms has only scarcely been reported. The aim of this paper was to present the idea that these 'channel' and 'ditch' habitats could in fact be a sanctuary for naiads. 2. Approximately 80 km of several of these Waterways fed by the mid Ebro River were sampled in Spain to monitor their naiad populations. Observations indicate that these habitats harbour substantial colonies of freshwater mussels (including two populations of adult specimens of the endangered species Margaritifera auricularia), much more so than the corresponding river. 3. The authors wish to alert conservation authorities and freshwater mussel experts to the extreme fragility and importance of this kind of habitat for the long-term conservation of these imperilled molluscs. Copyright (D 2008 John Wiley & Sons, Ltd.