The influence of water, diet, and temperature on 87Sr/86Sr in fin spines of juvenile Atlantic Sturgeon Acipenser oxyrinchus oxyrinchus

Analysis of microchemistry in fish fin spines offers a non-lethal approach to address key questions about life history specific movement and habitat use. Reconstruction of life history is based on chemical changes within calcified structures with an underlying assumption of elemental incorporation relative to environmental concentration. However, information on the relative contributions of water and diet to trace elements in calcified structures of fishes, including fin spines, is limited. Strontium (Sr) is commonly used in trace element studies because of its predictable changes within watersheds, with recent applications showing utility of ⁸⁷Sr/⁸⁶Sr for greater spatial resolution. In this study we evaluated the influence of water and diet ⁸⁷Sr/⁸⁶Sr on pectoral fin spines of Atlantic Sturgeon A. oxyrinchus oxyrinchus in controlled laboratory experiments. To understand the extent to which water and diet ⁸⁷Sr/⁸⁶Sr contribute to levels in fin spines, we exposed fish to one of four treatments for 12 weeks; a control, water spiked with ⁸⁷Sr, and diet spiked with medium and high levels of ⁸⁷Sr. To determine the amount of time it takes to elicit a shift in fin spine ⁸⁷Sr/⁸⁶Sr following a change in ⁸⁷Sr/⁸⁶Sr, fish were maintained in water- or diet-spiked treatments for up to 6 weeks. Lastly, we investigated how temperature may influence fin spine ⁸⁷Sr/⁸⁶Sr by holding fish at either 16 °C or 24 °C for 12 weeks. Our experiments indicated water is the primary contributor of ⁸⁷Sr/⁸⁶Sr levels in fin spines of Atlantic Sturgeon, and these levels shifted 1 week and 12 weeks following changes in water and diet, respectively. Water temperature did not have an effect on ⁸⁷Sr/⁸⁶Sr fin spine chemistry, although sample size was low (n = 3). These results provide guidance for interpretation of ⁸⁷Sr/⁸⁶Sr in pectoral fin spines of sturgeon and indicate usefulness of the technique for retrospectively estimating movement and habitat use.