Longitudinal and Temporal Elemental Signatures of South Dakota Missouri River Tributaries

The microchemical composition of fish otoliths is a “biological tag” that reflects the use of different habitats throughout the life history of a fish.  Because it is assumed that the otolith signature at an annulus directly reflects that of the water in which that fish lived at that given time, documenting the signatures of water is important.  However, signatures may vary between seasons and between years.  If substantial intra- and interannual variability exists, this may preclude the use of otolith microchemistry to answer research needs.  The objective of this study was to determine longitudinal and temporal patterns of trace element signatures of eight Missouri River tributaries.  A single water surface sample was collected from 36 sites from the headwaters to the confluence among eight tributaries during a two-week period in July and October 2013, and samples were analyzed for Ca, Sr, Ba, Mg, Mn, and Na concentrations using high-resolution, inductively coupled plasma mass spectrometry (HR-ICPMS).  Results from this study will be used to determine the feasibility of using otolith microchemistry to address potential fisheries research questions in the future.