Drift Initiation and Dynamics of Scaphirhynchus Sturgeon in the Lower Missouri River

Shovelnose sturgeon (Scaphirhynchus platorynchus) and the endangered pallid sturgeon (S. albus) have declined in the fragmented and highly modified Missouri River.  These species are hypothesized to spawn over coarse substrate, depositing adhesive eggs that develop on the substrate or in interstitial spaces.  Little is known about the free-embryo and larval life stages of ­these species.  Research from 2012–2015 involved field collection of drifting free embryos and larvae, modeling efforts to identify origins of collected free embryos, and laboratory experiments to characterize relative abundance and dispersal patterns of Scaphirhynchus sturgeon.  Shovelnose sturgeon free embryos and larvae were collected during an extended period.  Pallid sturgeon were rare; only 3 of approximately 1,090 sturgeon collected by U.S. Geological Survey.  All pallid sturgeon were collected on the same date during 2014.  Most sturgeon were collected near the high-velocity thalweg of the Lower Missouri River, indicating these species are likely to disperse long distances.  Both field collections and laboratory experiments indicate that dispersal for Scaphirhynchus sturgeon occurs immediately after hatch.  These results contribute to the understanding of dispersal patterns of Scaphirhynchus sturgeon and underscore the importance of identifying factors influencing successful pallid sturgeon spawning, incubation, hatch, and dispersal in the modified Lower Missouri River.