Lake sturgeon Acipenser fulvescens and shovelnose sturgeon Scaphirhynchus platorynchus environmental life history revealed using pectoral fin-ray microchemistry: implications for interjurisdictional conservation through fishery closure zones.

This study inferred that the majority of shovelnose sturgeon Scaphirhynchus platorynchus captured in the upper Mississippi River probably originated from locations outside the upper Mississippi River (Missouri River, middle Mississippi River); whereas, lake sturgeon Acipenser fulvescens exhibit infrequent movement outside of the upper Mississippi River, but may move throughout these interconnected large rivers at various life stages. By using pectoral fin-ray microchemistry (a non-lethal alternative to using otoliths), it is suggest that interjurisdictional cooperation will probably be needed to ensure sustainability of the S. platorynchus commercial fishery and the success of A. fulvescens reintroduction in the upper Mississippi River. Additionally, fin-ray microchemistry can provide invaluable data to make informed management decisions regarding large river fishes, that cross jurisdictional boundaries or that move outside of closure zones, without causing further mortality to compromised fish populations (e.g. threatened and endangered species).

Relationships between water and paddlefish Polyodon spathula dentary elemental and stable-isotopic signatures: potential application for reconstructing environmental history.

The objectives of this study were to characterize relationships between water and paddlefish Polyodon spathula dentary Sr:Ca, δ18 O and stable hydrogen isotope ratio (δD) to determine the accuracy with which individual P. spathula could be assigned to their collection locations using dentary-edge Sr:Ca, δD and δ18 O. A laboratory experiment was also conducted to determine whether dentary Sr:Ca in age 0 year P. spathula would reflect shifts in water Sr:Ca to which fish were exposed. Significant linear relationships between water and dentary Sr:Ca, δD and δ18 O were observed, although the relationship between water and dentary δ18 O was weaker than those for Sr:Ca and δD. Classification success for individual fish to collection locations that differed in water Sr:Ca, δD and δ18 O ranged from 86 to 100% based on dentary-edge Sr:Ca, δD and δ18 O. Dentary Sr:Ca increased significantly in laboratory-reared age 0 year P. spathula following 4 weeks of exposure to elevated water Sr:Ca; dentary Sr:Ca of fish held in water with elevated Sr:Ca was also significantly higher than that of control fish reared in ambient laboratory water. Results indicated that P. spathula dentaries reflect water signatures for commonly-applied natural chemical markers and strongly suggest that dentary microchemistry and stable-isotopic compositions will be applicable for reconstructing P. spathula environmental history in locations where sufficient spatial differences in water chemistry occur.

Sturgeon and paddlefish (Acipenseridae) sagittal otoliths are composed of the calcium carbonate polymorphs vaterite and calcite.

This study sought to resolve whether sturgeon (Acipenseridae) sagittae (otoliths) contain a non-vaterite fraction and to quantify how large a non-vaterite fraction is using neutron diffraction analysis. This study found that all otoliths examined had a calcite fraction that ranged from 18 ± 6 to 36 ± 3% by mass. This calcite fraction is most probably due to biological variation during otolith formation rather than an artefact of polymorph transformation during preparation.

Otolith chemistry of prey fish consumed by a fish predator: does digestion hinder Russian doll techniques?

The effect of digestion by a predatory fish (largemouth bass Micropterus salmoides) on stable isotopic (delta(13)C and delta(18)O) and trace elemental (Sr:Ca and Ba:Ca) compositions of prey fish (bluegill Lepomis macrochirus) otoliths was investigated in a laboratory experiment. Trace element and stable-isotopic signatures of L. macrochirus otoliths were not significantly altered for up to 16 h after L. macrochirus were consumed by M. salmoides. Prey fish otoliths recovered from predator digesta can retain environmental stable isotopic and trace elemental signatures, suggesting that determination of environmental history for prey fishes by stable-isotope and trace-element analysis of otoliths recovered from stomachs of piscivorous fishes will be feasible.