BACKGROUND: Estuarine euryhaline teleosts as reared spotted scat will be continnously encounterd with alterations to water salinities. OBJECTIVES: The aim of the present study was to evaluate osmoregulatory capacity of the spotted scat in response to different salinities. METHODS: 120 fish were categorized into 4 groups of 30 fish each. The fish were transferred from the freshwater to different salinities (5, 10, 20, and 30 g/L) and kept for one month. Tissue sections of the secondary lamella and gill branches were staind using hematoxyline eosin and studied by the light microscope. RESULTS: Transfer from freshwater to different salinities made significant increase (p<0.05) in total chloride cells of the secondary lamella. Furthermore, while chloride cells alterations have been accompanied with decrease in the chloride cell numbers of the lamella such changes made an increase in chloride cell numbers of the gill branches. CONCLUSIONS: It can be concluded that the mentioned species has limited osmoregulatory capacity when encountering abrupt salinity changes.