Dam Removals Are Bringing Fish Back Across the Northeastern United States, Striking Down One Tiny Barrier at a Time

Dam Removals Are Bringing Fish Back Across the Northeastern United States, Striking Down One Tiny Barrier at a Time While the demolition of big dams in the West gets more attention, many of these often-obsolete obstructions are also coming out of northeastern streams and rivers—and herring are returning in droves Ben Goldfarb, bioGraphic October 16, 2026 Dams block the flow of a river to hold water in a reservoir, which can be used for agriculture, recreation, household needs or industry. The flow of water through a dam can generate hydroelectric power. Aging dams are being dismantled across the country, restoring the natural flow to rivers. Jukka Jantunen / Shutterstock In 1859, a committee of farmers in Billerica, Massachusetts, having grown irked by a dam on the Concord River, hired a surveyor to justify its destruction. The dam, which powered a textile factory owned by an industrialist named Charles Talbot, was allegedly flooding their fields and spoiling their hay; now they wanted the wall and its reservoir gone. They hoped the surveyor’s evidence would persuade a court to order its obliteration. The surveyor—a conscientious, lushly bearded man of good repute—set about plumbing the Concord’s bottom, measuring its bridges and scrutinizing high-water marks. In truth, he didn’t love the work, describing surveying as “drudgery” in his journals. Henry David Thoreau’s truest passion, of course, wasn’t surveying land, but writing about it. Aside from the paycheck, the now-legendary author had another motivation to take the Concord job: He despised the Talbot Mills Dam. A decade earlier, Thoreau had published the travelogue A Week on the Concord and Merrimack Rivers, in which he inveighed against the dam for blocking the passage of spawning fish, especially American shad. “Poor shad! Where is thy redress?” Thoreau wrote. Although Thoreau’s surveys supported the farmers’ case, on appeal, the state of Massachusetts permitted the dam to remain. This can’t have surprised Thoreau, who knew that dams made for intractable opponents. “Perchance, after a few thousands of years, if the fishes will be patient, and pass their summers elsewhere meanwhile, nature will have leveled the Billerica dam,” he wrote. The Talbot Mills Dam in Billerica, Massachusetts—shown in this 1908 photograph—has vexed environmentalists, agrarians and native fish for centuries. Public domain via Billerica Public Library For many fish-blocking dams, however, it hasn’t taken “a few thousands of years” to level them after all. Since 1912, more than 2,300 dams have been purged from waterways in the United States, most in the last quarter-century. The dam-removal movement hit its apogee in 2024, when, by the accounting of the nonprofit American Rivers, dam removals reconnected more than 2,500 miles of once-fragmented waterways. The year’s biggest and best-publicized dam obliteration occurred on the Klamath River, where the dismantling of four aging hydroelectric dams opened more than 400 miles of spawning habitat in California and Oregon to chinook salmon, which recolonized the watershed so rapidly that conservationists described the comeback as “magical.” Before the Klamath, the nation’s largest undamming took place on Washington State’s Elwha River, where two fish-blocking walls were obliterated on behalf of chinook, coho, steelhead and other salmonids. After this and other dams were removed from the Elwha River in Washington State, long-absent salmonids came surging back. Trish Drury / Alamy Stock Photo Yet it would be a mistake to presume that dam removals primarily benefit western salmon rivers. Though they’re typically smaller in scale and receive less fanfare, the majority occur in eastern states. In 2024, the Blake Higgins Dam came tumbling down in Vermont, the Edes Falls Dam departed the Crooked River in Maine, and the Kimball Brook Dam vanished from New Hampshire. Pennsylvania tore out 27 obsolete barriers that year, none taller than around 20 feet. Even the three-century-old Talbot Mills Dam that so vexed Thoreau may soon be taken down. “We’re in this dam-removal renaissance, where we’re losing barriers faster than we’re putting them up for the first time in history,” says Nathan Furey, a fish biologist at the University of New Hampshire. Per one inventory, however, at least 35,000 dams still truncate northeastern fish runs, including more than 3,000 in Massachusetts, 5,000 in Connecticut and 9,000 in New York. By the numbers: Klamath River dam removal The $500 million project to remove four dams along the Klamath River in California and Oregon took place over a couple of years, with the river flowing freely by August 2024. The work opened 400 miles of salmon habitat, and thousands of the fish passed a former dam site in both 2024 and 2025. Among the states destroying dams, albeit gradually, is New Hampshire, and one late-April morning I climbed into a car with Furey to tour a few of its newly free-flowing rivers. Furey had come to the Granite State in 2018 a neophyte to dam removal, having done most of his graduate research on relatively undeveloped Pacific salmon rivers in British Columbia. “But when you’re the fish guy at the University of New Hampshire, people want you to tell them what happens when a dam comes out,” he said as he navigated Durham’s leafy streets. “There’s a lot of people looking to you for answers.” Furey’s domain is the Great Bay watershed, a tidal estuary fed by an arterial network of seven rivers. Historically, those waterways teemed with a roster of diadromous fishes: species that split their lives between freshwater and the ocean. That included Atlantic salmon, shad, sea lamprey, American eels, tomcod, sturgeon and, most numerous of all, alewives and bluebacks, a pair of silvery, foot-long fish collectively known as river herring. Sharks, striped bass, cod, seals, seabirds and other predators devoured river herring as they approached the estuary each spring, and juvenile Atlantic salmon may even have timed their departure from river to ocean to coincide with alewives’ return. While cormorants and otters gorged on alewives, young salmon slipped downstream undetected. There’s safety in numbers, and alewives supplied such prodigious numbers before they crashed that one historian deemed them “passenger pigeons of the sea.” Alewives suffered as settlers expanded their presence in North America. Schuchart / Shutterstock Like their avian analogues, alewives fared dismally during North America’s colonization. Beginning in the 1600s, eastern colonists launched a dam-building spree, impounding and harnessing streams to spin waterwheels and power mills—gristmills for grinding corn, sawmills for hewing logs, paper mills for pulping wood, textile mills for spinning fabric. By the mid-1800s, more than 65,000 mills stapled eastern creeks, with catastrophic consequences. Over the past four centuries, scientists have calculated that New England’s dams have deprived its ecosystems of nearly 20 billion pounds of alewives—roughly the weight of 300,000 humpback whales. To show me what happens when one of those fish-blocking walls comes down, Furey took me to the Bellamy River, its frothing course previously straddled by a sprawling brick compound, former headquarters of Sawyer Woolen Mills. The textile mill, long defunct, had been converted to apartments in the 1980s, but its two dams had lingered, funneling the Bellamy through a narrow, fish-stopping pipe. As they aged, the dams also became flood hazards, and in 2019 and 2020 a coalition of agencies, nonprofits and the apartment complex’s owner demolished them. Now the unfettered river churns beneath the brick colossus, ripping over a recontoured bottom of bouldery pools and pockets. The dams are long gone, but can the herring navigate the obstacle course they left behind? “Alewives are not salmon—they can’t jump,” Furey explained over the Bellamy’s roar. “They’re not big, powerful swimmers like sturgeon; they’re not eels that can climb and crawl.” After the dams came out, the state attempted to count returning alewives with visual surveys—in other words, by staring at the stream and tallying fish, an obviously imprecise method. “We have no idea how many fish come back here,” Furey said. Furey had been tasked with answering that question. He and his students would capture alewives as they entered the Bellamy and implant them with trackers, including rice-grain-size microchips known as PIT tags, or passive integrated transponders, to figure out what percentage of returning herring managed to skitter through the rapids. We strolled past the apartment complex and upstream to watch Furey’s lab members set up the PIT tag reader that would register each fish. A metal box, containing batteries and a recorder, was chained to a tree near the bank; from it, a cable ran to a riffle, ready to log the serial number of any tagged alewife that wriggled past: a modern technology to surveil an ancient fish. Nathan Furey, a fish biologist at the University of New Hampshire, attempts to quantify how many alewives and other fish are returning to New England rivers after dams come down. Ben Goldfarb As Furey’s colleagues fiddled with the PIT tag array, they were observed with curiosity by the residents of the Sawyer Mills apartments, many of whom had taken their lunches outside to savor the balmy spring day. Whereas other wildlife migrations, like the trans-hemispheric flights of Arctic terns, unfold largely beyond human ken, New England’s diadromous fish often pass through neighborhoods and backyards. “They don’t need pristine environments—they can be right here,” Furey said.