AbstractThe goal of this study was to study the distribution of potential habitat markers (Sr/Ca, Ba/Ca, Mn/Ca and Li/Ca) in water from the Paranaguá Estuarine Complex (Brazil) and to study habitat use patterns of Cathorops spixii through ontogeny employing otolith microchemistry. Fish were caught from three sampling sites while water samples were collected at eight stations covering a salinity range from 4.5–33. Elemental concentrations in otolith and water were determined by LA-ICP-MS and ICP-MS, respectively. When the relationship between salinity and elements or ratios in water was studied, significant positive relationships were found for Sr, Li, Ca, Sr/Ca, and negative for Ba, Mn, Ba/Ca and Mn/Ca (P < 0.05). No relationship was observed between water Li/Ca and salinity. A significant positive correlation was found between otolith edge Sr/Ca and salinity (r = 0.63; P < 0.05), positioning this ratio as the best natural tag for reconstructing environmental histories of C. spixii. Change point analysis (CPA) based on otolith Sr/Ca signature through ontogeny revealed potential migrations between environments with different salinity. According to CPA, the number of displacements among different salinities ranged from 3–9 (6.1 ± 1.9), suggesting high plasticity in the migratory patterns. Ba/Ca, Li/Ca and Mn/Ca peaks were observed on the outer margin of the primordium, and could be influenced by physiological, environmental and maternal factors.