**The title, authors, and abstract for this completion report are provided below.  For a copy of the completion report, please contact the GLFC via e-mail or via telephone at 734-662-3209**

Determination of micro-elemental stability of sea lamprey statoliths

Aude Lochet², Ellen Marsden², Brian Fryer³, Stuart Ludsin⁴

² University of Vermont, Rubenstein Ecosystem Science Lab, 3 College Street,

Burlington, VT, 05401, USA

³ University of Windsor, Great Lakes Institute for Environmental Research, 406

Sunset, Windsor, ON, N9B 3P4, Canada

⁴ The Ohio State University, Department of Evolution, Ecology, and

Organismal Biology, Aquatic Ecology Laboratory, 1314 Kinnear Road,

Columbus, OH 43212, USA

June 2012

Abstract

Sea lamprey (Petromyzon marinus) is a nuisance species in the Laurentian Great Lakes and Lake Champlain. Information about which tributaries contribute individuals to the parasitic juvenile and spawning adult population is critical for appropriate allocation of efforts to control this species. Trace-element analysis of sea lamprey statoliths has been shown to reliably discriminate among larvae from different natal streams. However, its use for correctly identifying natal (tributary) origins of parasitic juveniles and adult spawners has proven less reliable, possibly owing to the drastic metamorphosis that occurs at the end of the larval stage. The objectives of our study were to test whether metamorphosis from a larva into a juvenile either altered the micro-elemental composition of statoliths or caused structural changes in statoliths. If so, it might limit the value of using larval statoliths to determine natal origins of juvenile parasites or spawning adults. We also aimed at documenting statolith growth with ontogeny. Our study neither provided evidence of structural reworking of statolith during metamorphosis, nor challenged the conventional understanding of statolith growth (where statoliths grow by addition of new material at their base). However, we identified a major limitation to the statolith micro-elemental approach; unlike their otolith counterparts, the micro-elemental composition of statoliths changes with metamorphosis. More precisely, the statolith material deposited at the larval stage is enriched in rubidium (Rb) during metamorphosis, which is problematic when Rb is a key element for successful discrimination of larvae produced in different spawning tributaries. We offer advice on how to address this limitation at the conclusion of this report.