Abstract
The effect of water salinity on the elemental composition of sagittae (otoliths) taken from male gobid fishes, Tridentiger obscurus obscurus, reared at a constant salinity (freshwater, 50% seawater and 100% seawater) for one month at 20°C, was studied using particle induced X-ray emission (PIXE). Nine elements were detected in the otoliths; Ca, Cl, Sr, K, P, Zn, Mn, Fe and Cu. The PIXE technique was proved to be an effective means for performing multielement analysis in small fish otoliths. The Cl, K and Sr concentrations, and each of their concentration ratios with Ca in the otoliths, were positively proportional to salinity of the fish rearing. The Mn and Zn concentrations, and Mn/Ca and Zn/Ca concentration ratios, were inversely proportional to the respective rearing salinity. No significant changes in Ca, P, Fe and Cu concentrations and P/Ca, Fe/Ca and Cu/Ca concentration ratios in the otoliths were found. These results suggest that it is possible to use the relationship between the elemental composition of otoliths and the environmental salinity as a means of reconstructing the salinity history of migratory fish.
