Identifying river of origin for age-0 Scaphirhynchus sturgeons in the Missouri and Mississippi rivers using fin ray microchemistry

Understanding linkages between natal and nursery habitats is critical for conservation of riverine fishes. Scaphirhynchus sturgeons inhabiting the middle Mississippi River may originate from the Missouri or Mississippi rivers, although relative importance of these recruitment sources is unknown. We characterized the relationship between water and sturgeon fin ray Sr:Ca, verified shifts in water Sr:Ca are recorded in age-0 sturgeon fin rays, and determined whether age-0 sturgeons from the Mississippi and Missouri rivers exhibited distinct fin ray Sr:Ca signatures. Fin ray Sr:Ca of laboratory-reared fish reflected transfer from water with elevated Sr:Ca to ambient water 1 day posthatch, indicating that short-term residency in environments can be detected. Nine of 30 age-0 fish captured in the middle Mississippi River were Missouri River emigrants. Four of these emigrants originated in the upper portion of the lower Missouri River (≥589 km upstream from its mouth), where water Sr:Ca is higher compared with the lowermost section of the Missouri River and the Mississippi River. Twenty-five of 30 fish collected from the lowermost section of the Missouri River originated within this river segment; the remainder originated upriver. Fin ray Sr:Ca enables identification of natal river segment for age-0 sturgeons and contributions of river segments to sturgeon recruitment.