Estimating Spatial Heterogeneity and Temporal Stability of Strontium Isotope Signatures for Use in Tracking Fish Movements

Over the last decade techniques for analyzing environmental chemical and isotopic signatures in otoliths have transformed the way researchers are able to track fish movement.  Studies which use these techniques rely on large spatial heterogeneity and high temporal stability of isotopic signatures. The level of spatial heterogeneity and stability of isotopic signatures varies across systems and is rarely understood prior to commencing a study due to the costly nature of collecting samples. Therefore, there is a need to understand the temporal stability of isotopic signatures and develop a cost effective tool to estimate the spatial heterogeneity of isotopic signatures across watersheds prior to sample initiation. Using the Upper North Platte River Drainage located in south-central Wyoming, as a model system, our primary objective was to explore the dynamics driving seasonal and annual stability in strontium isotope signatures and assess the feasibility of using bedrock geology as a predictive tool to estimate spatial heterogeneity of strontium isotopic signatures within the Upper North Platte River Drainage. Our results provide insight for future studies hoping to use strontium stable isotopes to assess fish movement.