Ear bones (otoliths) of fish have been used since the late 19th century to age fish, but ear bones can also be used as innovative tools to understand past environments and biological processes such as movement patterns. Otoliths accrete new material onto the exterior surface on a daily basis; as this occurs minor and trace elements are also incorporated along with the major constituents of carbon, oxygen and calcium. Hence otoliths provide a chemical chronology over the entire life of a fish. Quantifying and interpreting the chemical composition of fish otoliths is challenging, but can be used to explore life-history information. Determining movements from otolith chemistry relies on different chemical signatures or tags being incorporated from different environments. Groups of fish with similar tags can then be linked through space and time to determine where and when fish moved. Chemical signatures across an otolith can provide natural tags for several different life-history stages, which can then be related to the different environments the fish has lived in thereby demonstrating movement patterns. Multiple different approaches can be used to determine fish movement using otolith chemistry. What is required for each approach and the assumptions made differ. The aim of this keynote will be to introduce fish passage researchers and practitioners to how otoliths, in particular their growth patterns and chemistry, can be used to address ecological and fisheries questions around movement and connectivity of fish populations, as well as understanding environmental conditions that fish have experienced.