Migration is a widespread phenomenon among animals and has a profound influence on the evolution of species traits. Diadromous fishes are an extreme example of migration, moving between marine and freshwaters, often traveling thousands of kilometers for feeding and reproduction. Diadromous fishes include iconic species such as salmon, eels, shad, lamprey and sturgeon, yet the origins and evolutionary consequences of diadromy remain elusive. In this talk I will explore the evolution of diadromy spanning population to phylogenetic scales. I will evaluate a widely accepted hypothesis that links the origins of diadromy with productivity by integrating phylogenetic, biogeographic and global productivity data. Using phylogenetic comparative methods I will investigate the adaptive landscape of diadromous fishes to determine whether intraspecific variation predicts macroevolutionary phenotypic patterns in migratory fishes. Finally, using more than 100 years of natural history collections, I will trace the origin and evolutionary ecology of alewives introduced in the Great Lakes and compare these populations to native migratory populations from the East Coast of North America.