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

Abstract

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.

Spatial Gradients in Population Characteristics of Ohio River Sauger and Implications for a Length‐Based Regulation

“…Growth of Ohio River Sauger had a strong, positive relationship with distance downstream as Saugers in downstream pools grew faster and to larger sizes than those in upstream pools. The Ohio River decreases in latitude from its origin to its confluence, which corresponds to an increase in ambient temperature, and this may lead to faster growth rates (see also Abner and Phelps ). In addition, fish communities and habitats, in terms of water clarity, depth, width, and velocity, change longitudinally (Emery et al.…”

“…In large river systems, spatial gradients in environmental factors, such as temperature and discharge, can lead to gradients in fish population characteristics, including recruitment, growth, and mortality (e.g., Bratten and Guy ; Eder et al. ; Abner and Phelps ). Consequently, spatial differences in the effectiveness of fisheries management actions may exist in large river systems, including implementing MLLs (Eder et al.…”

The effect of temperature and acute hypoxia/hyperoxia exposure on swimming performance and kinematics of Freshwater Drum

“…Given that Freshwater Drum occupy the largest latitudinal range of any freshwater fish in North America, additional work with populations from other latitudes has the potential to show a latitudinal gradient in temperature effects on swimming performance and perhaps on other aspects of Freshwater Drum biology. Although there are published studies on temperature requirements, ecology, and growth dynamics of Freshwater Drum across the species' range (Wismer and Christie 1987;Wahl et al 1988;Rypel et al 2006;Jacquemin et al 2014Jacquemin et al , 2015Abner and Phelps 2018), other studies of swimming performance or bioenergetic responses to latitude, temperature, or flow rate for this species have not been published. As climate shifts continue to occur, changes in water temperature and DO are likely to interact to create stressful conditions to which fish populations may not have sufficient plasticity to adapt phenotypically or genetically (Earhart et al 2022).…”