Experimental and Field Evaluation of Otolith Strontium As a Marker to Discriminate Between River-Spawning Populations of Walleye in Lake Erie

Otolith microchemistry has seen rapid growth as a fish stock discrimination tool. For walleye in Lake Erie, previous research suggests that strontium (Sr) concentrations may be able to be used to distinguish walleye spawned in the Sandusky River from those spawned in the Maumee River. Important questions remain, however, as to the validity of this tool over the long term. In this study, we address the following questions: 1) Is larval river-residence time sufficient to allow otolith Sr concentration to reflect its concentration of the ambient water? 2) Do temperature effects on otolith Sr uptake rate affect our ability to distinguish between the two stocks? 3) Are inter-annual differences in environmental concentration of Sr great enough to affect our ability to distinguish between the two stocks? We used laboratory experiment and filed survey to answer these questions. We found that otolith Sr concentration provides a powerful tool to discriminate between these river stocks despite short larval river-residence time, variation in water temperatures, and inter-annual variability in environmental Sr concentrations.