As introductions of invasive freshwater mussels continue to be detected across the Western United States there is significant interest in understanding what waters are most at risk of infestation. In the absence of extensive laboratory studies on the physiological tolerances of invasive dreissenid mussels, correlative studies comparing mussel distribution and environmental parameters remains the best tool available for understanding the risk of mussel establishment in new waters. Previous efforts to define such habitat suitability parameters for dreissenid mussels have drawn primarily on data from waters in the Eastern US and Europe. Hydrological regimes in these regions are often less dynamic than in Reclamation waters in the arid Western US. We hypothesize that such factors may play an as yet unrecognized role in determining a waterbody’s potential risk of invasive mussel establishment and infestation, and may serve to limit the spread of infestations in Reclamation waters. The proposed work will draw on a decade of early detection research conducted at the Reclamation Detection Laboratory for Exotic Species (RDLES), as well as publicly available data on water quality and hydrology to understand what factors may control the establishment of mussels in the Western US. Of particular interest will be waterbodies where RDLES has identified evidence of dreissenid mussel introductions, but populations have not proceeded to establishment and infestation. These data suggest initial habitat suitability but that some environmental features limited population expansion and survival. This is significant because for waters where no detection has occurred, it is not necessarily possible to distinguish if this is due to unsuitable environmental conditions or simply a lack of any introduction. This project will assess how current habitat suitability models may be refined to more accurately inform risk assessment in Reclamation waters.
