Freshwater mussel distributions and habitat relationships in the navigational pools of the Allegheny River, Pennsylvania

The main-stem Allegheny River is nationally recognized for its freshwater mussel (Unionidae: Bivalvia) diversity, however, habitat disturbance and degradation may have triggered the decline and loss of mussel communities in the lower river, where lock and dam structures restrict the free-flow of water and create deep navigational pools. We examined mussel diversity and abundance across 75 transects throughout navigational pools and recorded 21 live native mussel species, including federally endangered Pleurobema clava (Clubshell) and Epioblasma torulosa rangiana (Northern Riffleshell). Riverine species richness and counts were significantly higher in the upper portions of the upper pools, indicating that areas with consistent flows and suitable substrate just downstream of the dams may provide refugia for riverine freshwater mussel species. These data will help identify sensitive areas for future protection and provide baseline data for monitoring future trends. The protection of relatively shallow areas with suitable substrates not yet impacted by dredging operations will be important to sustain remaining freshwater mussel populations in these pools.