Ontogenetic patterns in the calcification and element incorporation in fin rays of age-0 White Sturgeon

Abstract

White Sturgeon (Acipenser transmontanus) are a long-lived, slow-growing, and late-reproducing anadromous fish common in estuaries and coastal habitats along the North American West Coast. These life history characteristics make populations vulnerable to human impacts and a challenge to study and manage. Previous studies in the San Francisco Estuary, California have provided insights into rearing habitats and migratory patterns but are limited in spatial and temporal scope. Fin ray geochemical analysis can provide a non-lethal approach to reconstruct migratory patterns and environmental conditions experienced throughout an individual fish’s lifespan. However, it is not known how soon post hatch age-0 White Sturgeon fin rays begin to calcify, reducing confidence in early life history temporal resolution using geochemical approaches. We used osteological (clear and stain) and geochemical techniques (laser-ablation-ICP-MS) to describe calcification initiation and completion, and element incorporation in the leading fin ray of known-age White Sturgeon reared at constant water temperature (18.6 °C) from 1 to 76 days post hatch (dph). We found that fin rays begin calcifying as early as ~20 dph (~27 mm total length) and are >95% calcified by ~72 dph (~70 mm total length). Consequently, the first ~20 dph are not likely to be recorded in the fin ray. Observed element (Li, Mg, Cu, Zn, Rb, Sr, Ba, Pb, U) incorporation patterns suggest that fin rays can provide a powerful tool to study White Sturgeon early movement and migratory patterns, habitat use, and environmental exposure.