Alewife is a fish that lives mainly in the Great Lakes and along the Atlantic coast of North America. Alewives have large eyes, a forked tail, silvery sides, and a grayish-green back. Freshwater alewives measure 3 to 6 inches (8 to 15 centimeters) long. Saltwater alewives grow as long as 15 inches (38 centimeters). The saltwater variety is caught commercially for human food. The freshwater variety is used only for animal feed and fertilizer.
Saltwater alewives live along the Atlantic coast from the Canadian province of Newfoundland and Labrador to South Carolina. They swim in large schools. They are anadromous—that is, they migrate to freshwater rivers to lay their eggs. Each female lays approximately 10,000 to 100,000 eggs in the spring. The adults then return immediately to the ocean. The young swim to the ocean a few months later, after they have grown.
Alewives probably are not native to any of the five Great Lakes. It is not certain when they colonized Lake Ontario, but they were abundant there by the 1870’s. Alewives colonized the other four lakes after 1932. Sudden die-offs of alewives often occur during the spring in the Great Lakes. Scientists believe these die-offs may be due to sudden drops in water temperature.
