The continued spread of two invasive dreissenid bivalve species, zebra (Dreissena polymorpha) and quagga (D. bugensis) mussels, into the southwestern and western United States indicates the need for improving understanding of habitat requirements and constraints for both species. This report summarizes results from published literature and reports that describe physical and environmental characteristics often associated with dreissenids. For example, data from the studies reviewed for this report indicate that at ...