Macrohabitats of Freshwater Mussels (Bivalvia:Unionacea) in Streams of the Northern Atlantic Slope

The goal of this study was to predict the broad-scale (1-10 km) distributions of freshwater mussels from readily available macrohabitat descriptors. All six of the descriptors used (stream size, stream gradient, hydrologic variability, calcium concentration, physiographic province, and the presence or absence of a tide) had some predictive power, but stream size and tidal influence were the most effective predictors of mussel distributions. Unexpectedly, several mussel species typically occurred in calcium-poor waters, which I tentatively interpret as evidence that these species might not tolerate eutrophication. In general, the macrohabitat distributions of mussel species identified in this study correspond only moderately well to previously published, subjective assessments of mussel habitat use.