Evidence of Limited Recruitment of Pallid Sturgeon in the Lower Missouri River

Abstract

Pallid Sturgeon Scaphirhynchus albus are endemic to the Missouri and Mississippi river basins and are rare throughout their range. The species was listed as federally endangered with little to no evidence of natural recruitment. Since population augmentation was initiated as a recovery objective in the early 1990s, thousands of hatchery-origin Pallid Sturgeon have been stocked in the lower Missouri River (Gavins Point Dam [river kilometer 1,305.1] to the confluence of the Mississippi River [river kilometer 0.0]). Efforts to discriminate natural reproduction and recruitment of wild-origin Pallid Sturgeon from hatchery-origin fish has been hampered by tag loss in hatchery-origin sturgeon, inconsistent documentation of hatchery parental crosses, and the failure to collect tissue samples for genotyping all broodstock. However, the recent reconstruction of missing parental genotypes from known hatchery-origin progeny and from cryopreserved milt made it possible to examine Pallid Sturgeon recruitment. Therefore, our objectives were to 1) determine the likelihood that unmarked Pallid Sturgeon captured from the lower Missouri River were the result of natural recruitment and 2) examine the length distribution of wild- and hatchery-origin fish to determine if a difference exists by origin and examine the life-stage distribution. Genetic analysis showed that from 2003 to 2015, 358 “presumptive wild-origin” Pallid Sturgeon were captured in the lower Missouri River and the comparison between the length distributions of wild- and hatchery-origin fish did not provide any additional clarification into potential wild-origin fish. Low recruitment may be due to a small breeding population, high mortality of early life stages, hybridization with Shovelnose Sturgeon Scaphirhynchus platorynchus, or transport of drifting free embryos or larvae into inhospitable habitats. Determining what factors are limiting recruitment is the important next step for the recovery of Pallid Sturgeon in the lower Missouri River.

Characterization of Pallid Sturgeon ( Scaphirhynchus albus ) Spawning Habitat in the Lower Missouri River

“…Until recently, researchers have been unable to detect reproduction and recruitment (Dryer & Sandvol, ; USFWS, ). Given small population sizes with few reproductive adults, the apparent paucity of natural reproduction and recruitment in the Lower Missouri River (LMOR) nearly 30 years after listing is concerning from a species conservation perspective (Steffensen et al, ), (Figure ).…”

Macroinvertebrate drift patterns in the Mississippi and Missouri Rivers: Implications for Scaphirhynchus sturgeon conservation efforts

“…With the consideration that population dynamics may be driven by resource accessibility, changes in these rates can negatively influence fish populations Phelps, Tripp, Hintz, et al, 2010). In the MMR and lower Missouri River, Scaphirhynchus sturgeon have experienced increased mortality and decreased recruitment (Birstein, 1993;Boreman, 1997;Colombo et al, 2007;Keenlyne, 1997;Phelps et al, 2013;Steffensen et al, 2019;Tripp et al, 2009). These factors have been attributed as leading causes…”

Floodplain connectivity and age‐0 sturgeon prey consumption in the lower Missouri River

“…Both shovelnose sturgeon (Scaphirhynchus platorynchus) and pallid sturgeon are considered rheophilic main-channel specialists (Gutreuter, Vallazza, & Knights, 2010;Hamel, Spurgeon, Pegg, Hammen, & Rugg, 2016;Steffensen et al, 2019), but little information exists regarding specific habitat requirements for these species.…”