Chemical analysis of otoliths: Cross validation between techniques and laboratories

Otolith microchemistry is a powerful tool for fisheries biology, but many applications stretch the limits of analytical techniques. Sources of measurement error were evaluated with a methodological comparison of solution and laser ablation inductively coupled plasma mass spectrometry at two laboratories, using otoliths and certified reference materials NIES-22 and FEBS-1. The intercalibration exercise was effective for Na, Ca, Zn, Cu, Sr, Ba, and Pb. Measurements of Sr were most robust, i.e. sensitivity, accuracy, and precision were least affected by laboratory, technique or sample type. Calcium and Ba measurements varied more between laboratories than between techniques. Lead and Cu measurements were more dependable across laboratory and technique while Zn measurements were more sensitive to these effects. Because the measurement of otolith elements may vary with methodology, it is imperative to consider the sensitivity, accuracy and precision for each application as the suite of elements of interest may differ. The development of reference materials has been the first step in standardization of the procedures, but there is a need for wider ranging calibration and comparison studies.