The original geographic range of smelt was along the eastern coast of North America. Although this species was primarily anadromous, many native landlocked smelt populations are located along the east coast and in the St. Lawrence River area. Early in this century, smelt were introduced into waters connecting to the Great Lakes, and by the 1930's, smelt had greatly expanded their geographic range, having spread throughout all of the Great Lakes; presently smelt are a dominant pelagic species in the Great Lakes. Since then, this species has invaded many inland lakes of eastern Canada. Smelt prey heavily on young-of-the-year fish, and their introduction into lakes has led to major declines of native species, particularly lake trout, whitefish and cisco. In addition, the introduction of smelt into lakes also leads to increased levels of PCB's and mercury in top predators such as lake trout.