Thermal tolerance of fish to heatwaves in agricultural streams: What does not kill you makes you stronger?

Heatwaves are increasing in frequency and intensity under climate change. Freshwater ecosystems are among the most thermally impacted systems, within which agricultural streams are experiencing the most extreme heatwaves and deserve prioritized focus. Heatwaves are approaching the upper thermal limits of many fishes but have received little attention to date.

To study whether and how fish tolerate heatwaves from a physiological perspective, we simulated single, multiple, and extended heatwaves at 32 and 34 °C in the laboratory, based on high-resolution summer temperatures recorded in agricultural vs. forested streams in Illinois, USA.

By investigating the effects of heatwaves on 25 °C acclimated fathead minnow Pimephales promelas, an important prey species across North America, we witnessed its high thermal resilience, including a rapid return to metabolic homeostasis after single and multiple heatwaves, measured by oxygen consumption rate (ṀO2). During extended heatwave, fathead...