Determining the Ecological Consequences of the Historical Damming of New England Watersheds

Anadromous river herring, collectively alewives and blueback herring, were historically abundant in most northeastern U.S. coastal river systems. Dam construction, which disrupted diadromous fish migration pathways, is considered the earliest principal cause of reduced productivity and population declines. Using published surveys, GIS layers, and historical documents, we developed a database of dams constructed throughout New England watersheds from 1600-present for the purposes of estimating a timeline of lost access to river herring spawning sites as a proxy for abundance. To evaluate the effect of reduced productivity on lake food webs, we collected juvenile alewives and freshwater predator fish from twenty coastal ponds in Massachusetts. Using diet analysis of predator fish and predator health, we can investigate the relationship between juvenile alewife consumption and the relative health of predator species. Results will be used to develop a better understanding of the ecological importance of alewives in freshwater systems, and how the ecosystems have been altered by dams.