The Influence of Temperature Variability On Fish Survival, Growth, and Early Life History

Many fish species experience dramatic temperature variation arising from a variety of natural and anthropogenic processes including upwelling events, diel vertical migration, and industrial thermal discharges.  We conducted laboratory experiments to understand how the magnitude and duration of temperature fluctuations affect multiple life stages in fish.  We separately exposed adult yellow perch and juvenile walleye to one of three treatments for 45 days: a constant temperature or 12-hour fluctuations of either ±2 °C or ±4 °C.  Survival was not affected by treatment in either species.  Yellow perch increased consumption and growth rates when exposed to extreme fluctuations, but also displayed signs of reduced health (e.g., high frequency of lesions).  Walleye growth rates decreased under even minor temperature fluctuations but no additional adverse effects were apparent.  To understand how early life stages are affected by temperature variation, we also compared fathead minnow egg incubation time, hatching success, and larval survival when exposed to multiple constant and fluctuating temperatures.  Elucidating fish responses to temperature variability is important because of population-level implications for size distributions, survival, and recruitment success.  Moreover, future climate change will likely increase the frequency and magnitude of temperature oscillations experienced by fish, necessitating further study of temperature variability.