Map of the study area and sampling localities. The Upper Mississippi River (UMR) study area (light green shading) and fish survey localities (blue points) are mapped over major administrative and physiographic features, including States (thin black lines; also labels for those through which the UMR flows), major rivers and lakes (blue lines and shading) and Long Term Resource Monitoring Program (LTRMP) study areas (thick grey lines). The LTRMP study reaches or “field stations” are defined by the sampled areas and labelled 1–6 (for additional details, see text and accompanying Mendeley Data accession, with archived version: http://dx.doi.org/10.17632/8s7vmk4jct.1). Several river systems named in the text are labelled in italics.