Evaluating Four Fish Species for Stress Caused By Intermittent Exposure to Warm Temperature

Temperature cycles throughout the day mean that even on the warmest day fish may be exposed to stressful warm temperature for only part of the day. Successive warms days will result in repeated intermittent exposure to temperature above the stress threshold. It is assumed that fish experience damage when the temperature exceeds the threshold, which will depend upon species and acclimation conditions, and will repair this damage when temperature falls below the threshold. If a species is not able to completely repair the damage before the next diel cycle, then damage will accumulate over successive cycles and sub-lethal and lethal effects may result. I used survival data from 30 day laboratory experiments with four fish species to develop and evaluate damage-repair models of intermittent exposure to warm temperature in response to a diel thermal cycle. There were important differences among golden shiner, smallmouth bass, walleye and white sucker in the threshold temperature above which damage occurs and their ability to repair damage caused by warm temperature. Most interesting was that golden shiner and walleye had a similar threshold temperature, but golden shiner had a greater capacity for repair, which prolonged their ability to tolerate stressful temperature. Both the stress threshold and capacity for repair may be important for predicting how fish communities will be affected by warming temperature.