Identifying River of Origin and Movements of Adult Scaphirhynchus Sturgeon Using Fin Ray Microchemistry

The pallid sturgeon Scaphirhynchus albus is endemic to the Missouri and Mississippi River drainage, though populations of this species have declined significantly due to overexploitation and anthropogenic degradation of these rivers.  The pallid sturgeon has experienced substantial declines because of similar appearance to its congener, the shovelnose sturgeon S. platorynchus, which has been exploited in the Mississippi River basin due to demand for caviar.  We sought to identify the origins and movements of pallid sturgeon throughout the Missouri and Mississippi Rivers in the central United States.  The unique geology along the cline of large rivers produces varying concentrations and ratios of trace elements (e.g., strontium [Sr], calcium [Ca], or Sr:Ca).  Adult pallid and shovelnose sturgeon fin rays were collected from the middle Mississippi River (between St. Louis, MO and the confluence of the Ohio River), then sectioned and prepared for microchemistry analysis at the University of Massachusetts, Boston.  Data were reported as Sr:Ca ratios (mmol/mol).  Our data indicate both the Missouri and Mississippi Rivers contribute to sturgeon populations in the middle Mississippi River.  Understanding the magnitude and timing of pallid sturgeon movements greatly enhances our ability to identify river reaches important to pallid sturgeon life history to focus conservation efforts.