This paper in the journal BioScience explores the impacts of dams in New England on alewife and blueback herring, which have been cut off from 90 to 95 percent of their historic spawning habitat. The loss of these species – collectively known as river herring – from lakes and streams has removed a major source of prey for an array of predators. In this paper, researchers estimate the impact of this loss of habitat connectivity. This loss has reduced the amount of forage fish in both New England lakes and in the ocean, and it has reduced the transfer of nutrients to lakes from the ocean. The authors suggest that managing to improve the connection between freshwater and marine systems could provide significant ecological and economic benefits, including increased productivity for recreational and commercial fishing.
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Mattocks, S., Hall, C. J., Jordaan, A. 2017. Damming, Lost Connectivity, and the Historical Role of Anadromous Fish in Freshwater Ecosystem Dynamics. BioScience, 67 (8), 713-728. doi: 10.1093/biosci/bix069.