Pairing lab and field studies to predict thermal performance of wild fish

In thermally variable ecosystems, temperatures can change extensively on hourly and seasonal timescales requiring ectotherms to possess a broad thermal tolerance (critical thermal minima [CTmin] and maxima [CTmax]). However, whether fish acclimate in the laboratory similarly as they acclimatize in the field under comparable thermal variation is unclear. We used temperature data from a tidal salt marsh to design 21-day lab-acclimation treatments (static: 12, 17, 22, 27 °C; daily variation with mean 22 °C: i) range 17-27 °C, ii) range 17-27 °C with irregular extremes within 12-32 °C). We compared thermal limits in lab-acclimated and field-acclimatized eurythermal arrow goby (Clevelandia ios). Variable temperature-acclimated and acclimatized fish had similar CTmin and CTmax. Notably, arrow gobies showed rapid plasticity in their absolute thermal tolerance within one tidal cycle. The daily mean and max temperatures experienced were positively related to CTmax and CTmin, respectively. This study demonstrates that ecologically informed lab acclimation treatments can yield tolerance results that are applicable to wild fish. •Monitoring temperatures in a tidal salt marsh alled us to characterize the natural thermal conditions of wild fish.•Field temperatures were used to design ecologically relevant field and lab studies on eurythermal fish, arrow gobies.•Thermal tolerance was similar among field-acclimatized and lab-acclimated individuals under comparable fluctuating temperatures.•In both field and lab, fish exhibited rapid plasticity (within hours) in their thermal tolerance.•Static acclimations predictably increased upper and lower thermal tolerance limits with increasing acclimation temperature.