In fall 2016, dreissenid or invasive mussel larvae were detected in Tiber Reservoir with a suspect detection in Canyon Ferry Reservoir. Invasive mussels are referred to as ecosystem engineers because of their profound effects on lake and river ecosystem function and structure. Since their discovery in the Great Lakes in the late 1980s dreissenid mussels have caused substantial economic impacts.

With the imminent threat of additional dreissenid mussel introduction, managers and policy makers in Montana need cost estimates to inform decisions about the appropriate level of investment in prevention programs and efforts at containing existing detections. The objective of this research was to provide estimates of the potential economic damages due to dreissenid mussels.