Statolith microchemistry as a technique for discriminating among Great Lakes sea lamprey (Petromyzon marinus) spawning tributaries

Laurentian Great Lakes fishery management agencies are seeking ways to identify natal origins of parasitic- and spawning-phase sea lamprey (Petromyzon marinus) so that efforts to control this invasive species can be prioritized. We developed laser-ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) as a technique to quantify elemental concentrations in larval sea lamprey statoliths and explored the use of statolith microchemistry as a tool to discriminate among larval sea lamprey production streams. Our analyses demonstrate that (i) traversing across the statolith with the laser is preferable to drilling down through its apex, (ii) preserving specimens in 95% ethanol versus freezing them has minimal effects on elemental concentrations, (iii) a minimum of 15 individuals per stream should accurately depict stream-specific statolith elemental signatures, and (iv) LA-ICP-MS is preferable to particle-induced X-ray emission (PIXE) for statolith analysis, based on higher precision, lower cost, reduced sampling-time requirements, and wider availability. Using LA-ICP-MS, we could discriminate among larvae from 13 streams located in Lakes Michigan, Huron, and Superior with 82% classification accuracy, indicating that this tool holds promise for determining natal origins of sea lamprey in the Great Lakes.