Key, K.N., A.E. Rosenberger, G.A. Lindner, K. Bouska, and S.E. McMurray. 2021. Riverscape-Scale Modeling of Fundamentally Suitable Habitat for Mussel Assemblages in an Ozark River System, Missouri. Freshwater Mollusk Biology and Conservation 24: 43-58.
Identification of the physical habitat characteristics associated with riverine freshwater mussel assemblages is challenging but crucial for understanding causes of mussel declines. The occurrence of mussels in multi-species mussel beds suggests that common physical factors influence or limit the occurrence of multiple species. Fine-scale geomorphic and hydraulic factors (e.g., scour, bed stability[A1] [A2] ) are predictive of mussel bed occurrence, but they are computationally challenging to represent at intermediate, or riverscape scales. We used maximum entropy (Maxent) modeling to evaluate associations between riverscape-scale hydrogeomorphic variables and mussel bed presence along 530 river km of the Meramec River basin, USA, to identify river reaches that are fundamentally suitable and unsuitable for mussels. Locations of mussel beds were obtained from an existing, multi-year dataset, and river variables were derived from high-resolution, open-source datasets of aerial imagery and topography. Mussel beds occurred almost exclusively in reaches identified by our model as suitable, which were characterized by laterally stable channels, absence of adjacent bluffs, proximity to gravel bars, higher stream power, and larger areas of contiguous water (a proxy for drought vulnerability). We validated our model findings based on model sensitivity using a set of mussel bed locations not used in model development. These findings can inform how resource managers allocate survey, monitoring, and conservation efforts.