Differences in elemental chemistry and C-O stable isotope composition between left and right otoliths of a flatfish, the common sole solea solea

Abstract

International audienceTo test the hypothesis that both otoliths (left and right sagittae) of a flatfish, Solea solea (Linnaeus, 1758), display the same elemental fingerprint information, we analyzed whole-otolith preparations from coastal lagoons and marine sites in the NW Mediterranean for the presence of 15 elements (Li-7, Mg-24, Al-27, Ca-44 Cr-52, Mn-55, Fe-56, Co-59, Ni-60, Cu-63, Zn-68, Sr-86, Cd-111, Ba-137 and Pb-208) their ratio to Ca and for carbon and oxygen stable isotope ratios. We found significant concentration differences between the two otoliths for two elements, i.e. Li-7 (right > left) and Sr-86 (right > left) all sites pooled together. However, this general trend differed between sites, with coastal lagoons showing significant differences for additional elements between the two otoliths, such as Ca-44 and Ba-137 in coastal lagoons for small juveniles, Mn-55 and 68Zn in coastal lagoons for larger juveniles, and for Mn-55/Ca-44 for adults in marine sites. Both delta O-18 and delta C-13 isotopic ratios were higher in the right than in the left otolith (a difference of similar to 16% between otoliths in both cases) but these trends were not statistically significant and showed no spatial pattern. The left otolith was significantly heavier than the right otolith, a difference which decreased significantly with increasing fish size. Otolith mass was shown to correlate significantly with the delta O-18 and delta C-13 ratios, as well as for concentration in some elements and their ratio to Ca for both otoliths (Mn-55, Zn-68, Sr-86 and Ba-137) and for Al-27 on the left otolith only. Our results imply that the two otoliths are not interchangeable for fingerprint analysis. The right vs. left difference for Ca-44, Sr-86 and Ba-137 decreases with increasing fish size, which suggests that differences in element concentrations may he at least partly driven by fish size. Thus, fish physiology and inner ear functioning may differ between otoliths in intensity and/or type of process as a function of increasing fish size and so possibly explain left vs. right differences in the otoliths of S. solen