Direct relationship between water and otolith chemistry in juvenile estuarine triplefin Forsterygion nigripenne

Temporal fluctuations of physicochemical variables within estuaries present challenges in the use of otolith chemistry as a proxy to fish habitat use. Therefore, validating the relationship between ambient water and otolith chemical composition in a controlled environment before employing the technique is of great value in reconstructing life history of a fish species. In the present experiment we reared juveniles of estuarine triplefin at three Sr and Ba concentrations and two salinity levels for a period of six weeks. Analyses of otoliths using Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) indicated that Sr:Ca and Ba:Ca in otoliths were directly and linearly related to their respective concentration in the rearing water. However, enhanced uptake of Ba with increasing Sr concentration was also observed. Overall, the effect of salinity on otolith Sr:Ca and Ba:Ca was found to be limited. Our results confirmed that otolith trace element analysis is a reliable technique to decipher migration pattern of fish that move between waters with different Sr:Ca and Ba:Ca compositions.