Dentary Bone Chemistry as An Indicator of Environmental History for Paddlefish

The paddlefish (Polyodon spathula) is an important commercial and recreational species in the United States. Improved knowledge of recruitment sources and habitat use by paddlefish during early life (age-0) would be valuable to conservation of this species. Trace element composition of fish hard parts (e.g., otoliths, fin rays and spines) has emerged as a powerful technique to identify natal environment and reconstruct environmental history of many fish species.  Dentary bones are the primary aging structure for paddlefish, but whether dentaries reflect environmental chemistry analogous to otoliths and fin rays or spines in other fish species is unknown. The purpose of this study was to evaluate the use of dentary bone chemistry as a natural marker of environmental history for age-0 paddlefish. Dentaries obtained from paddlefish whose environmental history was known were used to characterize the relationship between water and dentary Sr:Ca.  We also investigated the uptake and sources of Sr in dentary bones in a laboratory experiment.  A regression relating water and dentary Sr:Ca was used to infer natal environment of age-0 paddlefish collected from the middle Mississippi River (MMR) during 2010 and 2011.  Dentary core Sr:Ca of age-0 paddlefish collected from the MMR indicated that 56% of these fish were of Mississippi River origin, 30% were immigrants from the Missouri River, and 14% were of uncertain origin.  Our results indicate that multiple natal environments contribute to age-0 paddlefish present in the MMR.  Dentary microchemistry may also be applicable to paddlefish populations in other locations where spatial differences in water chemistry exist.