SRP182036 PRJNA516905 Habitat Use and Population Structure of the Shoal chub (Macrhybopsis hyostoma) in the Upper Mississippi River Basin Anthropogenic alterations of river systems may have a profound effect on native fish community and habitat use; however, it's difficult to understand the extent of these impacts without well-defined habitat preferences. We investigated the Shoal chub, Macrhybopsis hyostoma, a native obligate river species from nine sampling locations in the upper Mississippi River Basin (UMRB). Field surveys demonstrated that overall Shoal chubs preferred tributaries, yet this was statistically significant only for gravid females. Diet analysis and comparative morphology suggested that the Shoal chub is insectivorous and prefer benthic habitats. Our analysis of habitat use suggested that juvenile Shoal chubs preferred sand substrate and adults preferred medium to large gravel. Shoal chubs developed more melanophores as they aged, which is a likely an adaptation to their habitat shifts. The field survey identified possible sites where spawning was occurring and may be important for future conservation efforts for the Shoal chub. In addition, we conducted population genomic analysis of Shoal chub samples collected from the streams in three Midwest states (Illinois, Missouri, and Nebraska) and found low genetic diversity among the chubs that raises a concern in conservation. This preliminary study provides insights into further investigation of the impact caused by stream habitat alteration on native species and into the conservation of Shoal chubs in the UMRB.