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 degrees C or 24 degrees 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.