Dorsal Scutes: An Otolith Alternative to Infer the Origins and Life Histories of Shortnose Sturgeon (Acipenser brevirostrum)

The imperiled status of sturgeon worldwide places great importance on elucidating individual life histories. Examination of the microchemical properties within calcified structures has proven useful for gathering such information, yet focuses heavily on structures requiring lethal or injurious sampling. We propose dorsal scutes from sturgeon as a non-lethal alternative to otoliths and fin rays for inferring life histories and movements of sturgeons. Specifically, we assessed the capacity of scutes as structures that record chronological microchemical profiles. Dorsal scutes and pectoral fin spines were collected from wild and hatchery-reared individuals. Scute structure included apparent annuli that correlated with annuli counts in fin rays, a structure commonly used to age sturgeons. The strontium:calcium ratio in scutes and fin spines from hatchery fish was stable and relatively low, reflecting stable fresh water rearing conditions. In contrast, strontium:calcium ratios in scutes and fin spines from wild individuals showed the lowest ratios in inferred first and second years with higher values in later years, consistent with increasing use of estuarine and marine habitats with ontogeny. Discriminant analysis of elemental profiles measured during the presumptive juvenile period showed high assignment success. These findings are promising for reconstructing sturgeon life histories and discriminating rivers of natal origin.