Too hot for comfort: Elevated temperatures influence gene expression and exceed thermal tolerance of bigmouth shiners, <scp> <i>Ericymba dorsalis</i> </scp>

Environmental and associated ecosystem change may affect the persistence of fish species based on their ability to adapt to changing conditions, including decreasing flows and rising water temperatures. Exceeding the thermal tolerances of stream fish will likely result in a loss of ability to maintain metabolic processes. We evaluated the critical thermal maximum (CTmax) of bigmouth shiner (Ericymba dorsalis) and analysed the expression of heat shock protein 70 messenger RNA (mRNA) (HSP70) to quantify a thermal stress response over a gradient of temperatures (25°C-31°C). E. dorsalis HSP70 mRNA expression was upregulated in response to temperatures >25°C, indicating a stress response. This study supports the existence of a thermal stress threshold for E. dorsalis. The frequency at which this threshold is exceeded may increase under forecasted future climate scenarios for Nebraska.