Amazonian catfish make the longest freshwater migration in the world (5,000km). Dams being built could block this migration before we can even understand it completely. Similarly, largetooth sawfish make upriver movements from the Atlantic ocean but we do not know why. We have published one paper using isotopic tracers from fish earbones to reconstruct details of catfish migration and propose to expand our work and to include sawfish, another endangered megafish, in our isotopic migration study.