Developing Non-Lethal Methodology for Testing Thermal Optima and Tolerance in Small Prairie Stream Minnows

Regulatory agencies have dramatically improved implementation of water quality standards and stream health nationwide.  However, standards are typically set as threshold values based on lethal concentration tests, which are not adequately suited to measure sub-lethal physiological stressors that may adversely affect aquatic organisms.  Prairie stream fish are adapted to a highly variable thermal environment; therefore, their tolerance levels are likely not indicative of their thermal preferences or their relative capacity for acclimation to dominant thermal conditions.  Given that both ambient temperature and acclimation temperature affect swimming ability, we expanded on these findings by using swimming speed to measure potential growth for fish acclimated over a range of temperatures. Running thermal profiles at different starting acclimation temperatures, using swimming speed as an indicator of physiological performance, we constructed a maximum swimming speed-temperature relationship that shows both thermal tolerances and preferences of our model species, the Red Shiner, (Cyprinella lutrensis), while accounting for acclimation potential.  We found that swimming performance optimum was between 13.3°C and 27.6°C depending on the acclimation conditions.