AUTHORS: Ella Humphrey, University of Nebraska Lincoln; Jonathan Spurgeon, U.S. Geological Survey & Nebraska Cooperative Fish and Wildlife Research Unit; Sarah Sonsthagen, U.S. Geological Survey & Nebraska Cooperative Fish and Wildlife Research Unit
ABSTRACT: Climate change may impact the persistence of fish species based on their ability to adapt to changing environmental conditions, such as decreasing flows and rising temperatures. Fish rely on temperature regimes within their thermal tolerance to maintain metabolic processes. Thus, temperatures outside these tolerances will result in fish losing the ability to continue metabolic processes resulting in severe stress or death. Bigmouth shiner Hybopsis dorsalis is widespread throughout Nebraska and previous studies indicate that increasing temperatures may affect their range. Therefore, we evaluated the critical thermal maximum (CTmax) of H dorsalis and analyzed their expression of heat shock protein 70 (HSP-70) to quantify a thermal stress response over a gradient of temperatures (25-31°C). We found that HSP-70 expression was upregulated in response to temperatures >25°C, indicating a stress response. We then compared this thermal threshold to the yearly maximum temperatures from 42 rivers and streams in Nebraska to determine areas where H dorsalis may already be at risk for thermal stress within their range. About 88% of the sites surpassed 25°C at some point between May and September. This study provides evidence that H dorsalis may be experiencing thermal stress across Nebraska, which future climate scenarios may worsen.
