American shad, Atlantic salmon, river herring, and other anadromous fish migrate from the sea to freshwater to spawn, beginning life as small eggs laid in freshwater streams and following an ancient cycle that carries them from their birth streams to the cold waters of the Atlantic and back again to rivers like the Ashuelot, sometimes many times during their lives. Before European settlers came to New England, native people in the river valleys celebrated abundant spring runs of salmon and shad, catching them at waterfalls and rapids with spears, reed nets, and weirs of woven twigs and pliable bark; some fish were eaten immediately, while most were smoked and dried for winter food and trade, and the fishing season was also a time for treaties, speeches, and marriages. Beginning in the 1700s, settlers built small dams to power grist and saw mills on tributaries of larger rivers, blocking access to historic spawning and nursery habitats, and in less than a century, from the mid-1700s to the mid-1800s, the great fish migrations had nearly vanished from most New Hampshire rivers as over-fishing, thousands of dams and canals, and manufacturing waste further reduced shad and salmon. In 1968, state and federal agencies began planning to restore migratory fish to New England waters, and the 1977 Clean Water Act greatly improved river quality by regulating pollutant discharges, but restoring fish movement through rivers remained essential, leading agencies and private dam owners to build fish passages and remove unsafe or unwanted dams such as the McGoldrick and Winchester in hopes that migratory fish will one day return up the Ashuelot River.