Impacts of flow regulation on freshwater pearl mussel (Margaritifera margaritifera) habitat in a Scottish montane river

► We assessed the impact of flow regulation on endangered freshwater pearl mussels in a montane river in NW Scotland. ► Channel stabilisation and narrowing in response to regulation does not explain the unfavourable population status. ► Past pearl fishing, low host fish density and substrate compaction are hypothesized to have limited population recovery. ► The findings have implications for how the river could be managed to benefit the freshwater pearl mussel.