“…Otoliths are structures composed mainly of calcium carbonate deposited as aragonite, vaterite or calcite crystals in a protein matrix (otoline), and small quantities of other chemical elements (Campana et al ., 1997). These elements are deposited in the otolith during ontogeny and as the material is not re-absorbed, their concentrations may reflect the life history of the fish (Schuchert et al ., 2010; Mai et al ., 2014; Avigliano et al ., 2015a, b; Phung et al ., 2015; Reis-Santos et al ., 2015). In particular, divalent elements such as strontium (Sr) and barium (Ba), replacing Ca in the matrix of the otolith, have been widely used to study displacements in salt gradients (Doubleday et al ., 2014), with the premise that Sr in the otolith is positively related to salinity, while Ba shows the opposite behaviour (Bath et al ., 2000; Secor & Rooker, 2000; Kraus & Secor, 2004; Martin & Thorrold, 2005; Avigliano & Volpedo, 2013).…”