Concurrent Sessions B: Case Studies - Dam Impact Analysis Model for Atlantic Salmon in the Penobscot River, Maine

Agriculture Production Theater, Oregon State University

Dams are a major contributor to the historic decline and current low abundance of diadromous species, including endangered Gulf of Maine Atlantic salmon. We developed a population viability analysis to quantitatively evaluate the impact of fifteen federally licensed hydroelectric dams on Atlantic salmon population dynamics in the Penobscot River, Maine. We used a life stage-specific model to compare a salmon population under the current state of downstream dam passage success to scenarios with increased dam passage success and increased marine and freshwater survival rates. Adult abundance, distribution of adults throughout the watershed, and number and proportion of smolts killed by dam-induced mortality were used as performance metrics for each scenario. Adult abundance was sensitive to downstream dam passage survival rates and marine survival rates in all scenarios. Dams located on the mainstem of the Penobscot River had a greater impact on the Atlantic salmon population than dams located on tributaries, but all mainstem dams and all tributary dams did not affect the population equally. The combination of spatial location and passage success was important to the impact of each dam. This model will help prioritize future passage improvement efforts to maximize the benefits to the Penobscot River Atlantic salmon population and is adaptable for use with other diadromous species and river systems.