UMaine to Continue Studying Effects of Dam Removal on Sea-Run Fish Species

University of Maine researchers have received funding to continue to examine the impact of dam removal on freshwater systems and populations of sea-run fish such as Atlantic salmon, alewife, sea lamprey, rainbow smelt and American shad, and also begin new research on the effects of restoration of sea lampreys to waterways where sea-run fish can be found.

Stephen M. Coghlan Jr., an assistant professor of freshwater fisheries ecology in UMaine’s department of wildlife ecology, is leading the research, which includes monitoring changes in fish populations in the area of the Sedgeunkedunk Stream flowing through the Maine municipalities of Brewer and Orrington.

Sea-run fish, also known as anadromous fish, are migratory species that live mostly in the ocean but spawn in freshwater.

Dam removal has become a popular tool in Maine for rehabilitating runs of fish species and restoring marine-freshwater connections. In 2008-09, one dam along the Sedgeunkedunk was bypassed with a rock-ramp fishway and one dam was removed entirely. This has allowed sea-run fish to regain access to about 3.7 miles of stream habitat and 1,300 acres of pond habitat.

UMaine has been monitoring changes in the resident fish community since 2007 and changes in sea-run fish since 2008.

“The effects of the dam removal were very apparent within a few days of the removal,” Coghlan said. “We’ve gone back three times since then and what we’re finding from looking at our data is there is a pulse of fish moving upstream and fish densities are distributing themselves more evenly in the stream. It’s almost like the stream is functioning more as an integrated whole than a couple of different sections isolated from each other.”

The grant award of $33,582 from the National Oceanic and Atmospheric Administration (NOAA) also provides funding to test for the effects of sea lamprey colonization on changes in the condition of streams to the potential benefit of other species.

The researchers’ hypothesis, which is supported by results from their 2010 field research, is that the nest-building activities of sea lamprey, and the decomposition of the carcasses of dead sea lampreys, will improve conditions for salmon and other species.

Historically, Maine’s rivers, lakes, and streams provided spawning and nursery habitat for sea-run fishes, which likely provided important services to freshwater systems, such as transporting large quantities of marine-derived nutrients and energy (MDNE) that fertilized otherwise nutrient-poor habitats (primarily alewife but also sea lamprey), and removing fine sediment from streambeds during nest-building activities (primarily Atlantic salmon and sea lamprey).

Dams severed the link between marine and freshwater systems, causing a significant decline in most sea-run species and cascading effects onto freshwater and even terrestrial habitat.

Other UMaine researchers involved in the project are Joseph Zydlewski, an assistant professor of wildlife ecology and member of the USGS Maine Cooperative Fish and Wildlife Research Unit, and Kevin Simon, an assistant professor of biological sciences.

Contact: Stephen M. Coghlan Jr., (207) 581-2880 or; Jessica Bloch (207) 581-3777 or