Maine has removed a 60 year old ice control dam from the Narraguagus River in an effort to restore migration routes for endangered Atlantic salmon and other fish species.
The dam, located in Cherryfield was built by the US Army Corps of Engineers in 1961 to protect the town from ice jams and flooding. But the structure also blocked salmon, shad and river herring from reaching upstream spawning grounds.
Only about 25 wild adult Atlantic salmon have returned to the Narraguagus River annually in recent years, a sharp decline from the hundreds of thousands that once migrated through Maine’s rivers each spring.
The Gulf of Maine population of Atlantic salmon is listed as endangered under the US Endangered Species Act. Across Maine, only about 1,000 adult salmon return from the sea each year. Recovery targets call for at least 1,500 wild adults returning annually over multiple years for the population to move toward threatened status, while full recovery would require about 6,000 wild adults distributed across different watersheds.
The Cherryfield dam was the last major barrier on the main stem of the Narraguagus River. Although a fish ladder allowed some alewives to pass, salmon and shad often struggled to find or navigate it. Fisheries officials frequently observed adult salmon gathering below the structure.
As the ageing dam required increasing maintenance, Cherryfield could not afford to repair or replace it independently. Conservation organisations including the Maine Coast Heritage Trust, Downeast Salmon Federation, Atlantic Salmon Federation and The Nature Conservancy proposed removing the structure and replacing it with a nature like fishway.
In 2023, Cherryfield residents unanimously voted to take ownership of the dam from the Army Corps and remove it. Congress subsequently de-authorised the structure. The project received $9.1 million from NOAA’s Restoration Center through the Bipartisan Infrastructure Law, with construction beginning in June 2026 and expected to be completed by November.
The replacement fishway consists of a series of stepped pools designed to resemble a natural stream. The design is intended to allow fish to move upstream while slowing ice and reducing the risk of flooding in Cherryfield.
Scientists will monitor the effectiveness of the new passage using environmental DNA, or eDNA, from shad. Researchers are collecting water samples above and below the former dam site and sending them to the University of Maine in Orono for analysis.
Baseline samples collected in spring 2026, before the dam was removed, showed higher concentrations of shad DNA below the dam than above it. Researchers plan to repeat the sampling after the fishway is completed. Similar concentrations on both sides would indicate that shad are moving more freely through the restored section of the river.
However, removing the barrier will not eliminate the other threats facing Atlantic salmon. The Narraguagus lies near the southern edge of the species’ range, and its waters can become warmer than salmon can tolerate during summer. Atlantic salmon begin experiencing stress when temperatures rise above about 68 degrees Fahrenheit.
Scientists have used infrared cameras to map temperature variations along the river and identify cooler tributaries that could provide refuge for salmon. While parts of the main river become warm, some tributaries remain cold enough to support the species.
Maine’s remaining salmon population also relies heavily on hatchery programmes. Federal and conservation run hatcheries produce hundreds of thousands of eggs and juveniles that are released into rivers each year. In the Narraguagus, an estimated average of about 1,700 stocked juveniles survive to become smolts the stage when they migrate to the sea, but only a few dozen at most return as adults.
The federal recovery plan, updated in 2019, estimated that restoring the Gulf of Maine Atlantic salmon population could take about 75 years and cost more than $800 million.
Scientists consider Atlantic salmon an indicator of wider ecosystem health because the species depends on interconnected river systems supporting other fish, birds, mammals and freshwater organisms.
The removal of the Cherryfield dam is therefore one part of a much longer restoration effort. Reconnecting the river could provide salmon and other migratory fish with access to additional habitat but long term recovery will also depend on ocean conditions, warming rivers food availability and the survival of wild salmon over multiple generations.