In 2019, New Jersey completed the removal of the old Columbia Dam and reopened about 14 km of river; a 2026 study found juvenile eels, sea lampreys and American shad upstream after years of monitoring

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Columbia Dam in New Jersey was removed in 2019 to allow the natural migration of fish. Recent studies show encouraging signs of recovery in fish populations, including American eels and adult American shad. Researchers monitored the river for nine years to assess the ecological impact of the dam's removal. The dam's removal also resulted in measurable improvements in water quality, including changes in temperature and dissolved oxygen levels.