Examining the periodicity of annular deposition of otolith microconstituents as a means of age validation

In this study, we examined whether otolith microconstituents are deposited seasonally in a manner similar to optical annulus formation and thereby can be used to validate age interpretations. In temperate species, seasonal temperature changes drive the formation of optical annuli, and we hypothesized that they similarly caused oscillations in microconstituent deposition. Using laser ablation inductively coupled plasma mass spectrometry analysis, we tested for periodicity in the deposition of barium (Ba), calcium, copper, magnesium (Mg), manganese (Mn), phosphorus (P), strontium, and zinc in otoliths and compared that periodicity to the periodicity of the annulus zonation (optical opaque and translucent zones). For this investiga-tion of chemical annulus periodicity, we used black sea bass (Centropristis striata), a species with yearly optical annulus formation that has been val-idated. Periodicities in elemental pro -files in otoliths from black sea bass were detected by using Lomb-Scargle periodogram analyses. Optical annulus formation aligned with Mg profiles, but periodicity in annular deposition of other elements-Ba, Mn, and P- was observed only after the first optical annulus, an outcome that is indicative of ontogenetic changes in habitat (from coastal to near- shelf waters) known to occur during the juvenile life stage of this species. Certain elements, such as Mg, identified through this otolith analysis and the periodogram analyses could be applied to species for which no validated aging procedure exists.