The American shad, Alosa sapidissima , is an anadromous species which occurs along the Atlantic coast from southern Labrador to northern Florida. It also has been introduced along the Pacific Coast. American shad undergo extensive seasonal migrations, moving into rivers for spawning beginning in January in southern rivers, and continuing until July in the northernmost portion of their range. After spawning, shad migrate north along the coast to Canada where they feed during the summer. A southward migration occurs later along the continental shelf where the fish overwinter prior to spring spawning migrations to their natal rivers.
American shad have a range of life history patterns depending on their river of origin.
In southern rivers, shad return to spawn at age 4 and die after spawning. Fecundity ranges from 300,000 to 400,000 eggs. Progressing northward, increasing numbers of spawners survive, the mean age at first spawning increases to 5, and fecundity decreases to 125,000 to 250,000 eggs. Almost every major river along the Atlantic seaboard historically supported a spawning population of American shad. They have been exploited for their flesh and roe since prior to Euro-American settlement.