Since 2012, TNC has been working to restore the Paulins Kill, which was deteriorating due to disrupted river flow, increased water temperature, and degraded habitat. The first major and visible accomplishment was in 2018, when TNC and partners took out the Columbia Dam, an 18-foot-high, 300-foot-long barrier (and a separate remnant dam) out of the waterway in Knowlton. Combined with two additional upstream dam removals in 2022 and 2024, TNC’s action has reconnected 45 miles of river habitat in the Paulins Kill.
American shad spend most of their adult lives in the ocean and migrate up freshwater rivers each spring to spawn. They are an ecological anchor, cultural keystone, and historically a vital economic driver in the Delaware River Basin, but their populations have declined from overfishing, pollution, and dams that impede their reproduction.
TNC and partners first saw evidence of American shad above the Columbia Dam through environmental DNA (e-DNA) testing, which revealed genetic material the fish shed naturally in water samples from the area. In early August 2026, scientists caught several young-of-the-year shad during a night seining session in the Paulins Kill, verifying successful reproduction.
A biological process called imprinting helps guide American shad migrations. Young memorize the unique chemical scent, mineral blend, and taste of that specific water in which they hatch. After living in the ocean for three to five years, they use their memory and acute sense of smell to trace those signatures back home.
“It is an exciting development to confirm the presence of juvenile American shad in this stretch of the Paulins Kill where we have focused restoration efforts for almost fifteen years,” said Chloe Pearson, TNC’s freshwater science specialist in New Jersey. “These fish have an incredible natural imperative to return to their birth areas to spawn, and dams stop them from fulfilling this critical part of their life cycle. The baby shad we found in waters above the former Columbia Dam demonstrate that when rivers are freed of these antiquated barriers, fish return and successfully spawn.”
New Jersey’s rivers are obstructed by more than 1,700 dams. Most have outlived their intended purpose, but continue to disrupt fish movement, worsen flooding, and serve as safety hazards for people and communities. In the last eight years, TNC has led dam removals at three sites in the Paulins Kill and two in the Pequest, another Delaware River tributary. The projects serve as inspiration and models for others considering similar action.
New Jersey’s Statewide Dam Removal Partnership, led by TNC and including a consortium of nonprofits, agencies, and community leaders, is working to simplify processes, provide resources, enhance funding, and accelerate dam removals throughout the state. TNC plans to continue partnering with private landowners, local and state governments, and other nonprofit organizations to ensure the long-term health of freshwater resources and to improve public safety and community resilience in New Jersey.
