Abstract
Otolith microchemistry is a widely used technique for elucidating life history patterns in fishes. This typically involves sectioning the otolith and collecting elemental signatures via laser ablation. But this requires time-intensive handling that may influence results. As an alternative to traditional cut-polish-ablate techniques, we tested depth-profiling laser ablation, which offers reduced handling and contamination risk. To validate depth profiling as a robust method for collecting trace element otolith microchemistry data, we constructed composite otoliths using otolith materials from fishes of different origins (fresh water, seawater). Test ablations were conducted on composite diadromous otoliths at a range of spot sizes and pit depths. We measured tailing and fractionation effects in the following elements: Na, Mg, K, Mn, Zn, Rb, Sr, and Ba. Given appropriate instrument parameters, depth profiling can accurately collect elemental concentration data both between and within top and bottom layers of an otolith composite across a range of spot sizes and pit depths. Analytical power and lag effects were dependent on spot size, highlighting the importance of optimizing spot size based on sample morphology and instrument parameters.