Herring on their annual spring spawning run on June 12, 2026, just upstream of the Mystic Lakes Dam between Medford and, Arlington and Winchester, Massachusetts. In 2025, an estimated 815,000 herring swam from the ocean up the Mystic River toward Woburn’s Horn Pond, based on counts done by volunteers organized by the Mystic River Watershed Association in partnership with the Massachusetts Division of Marine Fisheries and the Massachusetts Department of Conservation & Recreation. Construction is scheduled to begin in summer 2026 on a fish passage at the Horn Pond’s Scalley Dam so more fish can get farther up river.
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