Latitudinal trends in Freshwater Drum population dynamics: Facing a changing climate

Latitudinal trends are present in multiple groups of organisms. Widely distributed species experience broad environmental gradients with differences in climate that translates to differences in dynamic rate functions. When evaluating widely distributed fishes in a large river system, one particular interest is the influence of latitude on recruitment, growth, and mortality. This study explored effects of latitude, and therefore climate, on the population dynamics of Freshwater Drum Aplodinotus grunniens along the Upper Mississippi River. Descriptive examinations of the dynamic rate functions indicated that freshwater drum populations from more northern locations experienced greater variability in recruitment, smaller maximum lengths, longer lifespans, and lower mortality rates than their southern counterparts. One potential hypothesis to explain these results relates to the temperature differences between more northern and more southern latitudes. For further explanation, individual regressions were computed between average temperature and population characteristics. These analyses suggested that temperature is a major driver of freshwater drum population attributes along this latitudinal gradient. Furthermore, we have demonstrated that a potential increased thermal regime (i.e., mid‐century and end‐century time climate change) will likely have pronounced influence on freshwater drum population characteristics. This research has implications for understanding population dynamics of widely distributed organisms in large riverine systems.