UMass Amherst: Despite modern designs intended to allow migratory fish to pass, hydropower dams on major Northeast U.S. waterways, including the Merrimack and Connecticut rivers, have failed to let economically important species such as salmon, shad and river herring reach their spawning grounds, say a team of economists and fish ecologists including Adrian Jordaan of the University of Massachusetts Amherst.
This raises serious questions about the impact of new dams now being planned and constructed on major waterways worldwide, say the researchers in the current issue of Conservation Letters. The international team led by J. Jed Brown of the Masdar Institute of Science and Technology, United Arab Emirates, included investigators at SUNY College of Environmental Science and Forestry, Syracuse; Virginia Tech, the University of Arizona, City University of New York and the University of Victoria, British Columbia as well as UMass Amherst.
They found that in spite of state-of-the-art fish passage facilities, actual numbers of fish passing through them over several decades reached only a tiny fraction of targeted goals. “It may be time to admit failure of fish passage and hatchery-based restoration programs and acknowledge that ecologically and economically significant diadromous species restoration is not possible without dam removals,” say Jordaan, Brown and colleagues.
The three river systems studied, the Merrimack, Connecticut and Susquehanna, are historically important for fish populations that migrate from the sea to spawn in rivers, known as diadromous species. They include sturgeon, salmon, shad, alewife, blueback herring and eel. Four of the nearly 20 dams studied are on the Susquehanna, with more than 10 on the Connecticut and five on the Merrimack. Jordaan points out that the Connecticut River watershed has more than 1,000 dams on tributaries, but those on the river’s main stem have the most impact on all species.
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