Validation in schlerochronology

Abstract

The broad range of otolith research and applications being carried out in recent years, points to an active field of science with increasingly diverse applications beyond traditional age determination: larval drift and connectivity, population dynamics, fish physiology, population tracking and environmental reconstruction. The main information encoded in the otoliths is based on the growth increments and in the geochemistry tags. The necessity to validate the temporal significanceof observed growth increments (i.e. periodicity of formation) was recognized early in the 1980’s (Beamish & McFarlane 1983). The recognition that ageing errors are important has stimulated interest in the validation of age estimation methods. Validation means proving that a technique is accurate and should be an obligatory step in all sclerochronological studies, and should include the evaluation of both accuracy and precision (Wright et al 2002). Validation is also an imperative in microchemistry studies where methodology is critical to the results, mostly because the heterogeneity of the samples and the low concentrations of many of its constituents. In addition, the supporting matrix of calcium carbonate, which makes up the majority of the mineralized portion of the otolith, causes interference and presents particular problems for analytical determination. With the recent increase in the number of studies based on otolith microchemistry, it is increasingly important that methods are standardized so that results from different laboratories can be compared across distances and years. Validation and standardization should include postmortem contamination of otoliths (i.e. handling and storage methods, cleaning procedures; otolith preparation (i.e. coring and pulverizing; to detection limits and accuracy and precision of the hardware (Geffen et al. 2013). In the present communication we aim to review the methodological validation techniques for two main otolith applications, to identify future challenges and ways to better link otolith Applications to other research fields