Aerobic scope and temperature preference in yellow tang (Zebrasoma flavescens) at current and elevated sea temperatures.

Climate change is predicted to continue elevating regional sea surface temperatures (SST) and increase the frequency and severity of localized heating events, phenomena which may threaten the biodiversity, integrity, and function of tropical coral reef ecosystems. The primary objective of this study was to determine physiological and behavioral responses to elevated SST in a Hawaiian surgeonfish, the yellow tang, Zebrasoma flavescens. We assessed standard metabolic rate (SMR), maximum metabolic rate (MMR), aerobic scope (AS), and swimming performance, as well as temperature preference (T_pref) in this ecologically and economically important coral reef fish. The Z. flavescens were acclimated to either the current maximum monthly summer SST around O'ahu, 27 °C, or an elevated SST, 31 °C. Acclimation temperature had no significant effect on SMR, MMR, AS, or swimming performance. Temperature preference was tested over a 24-hour period in an annular preference chamber with a gradient ranging from 24 to 34 °C. Our study found that Z. flavescens in both acclimation temperatures had a similar T_pref (median) of 27 °C with first and third quartiles of 25.7 to 29 °C. Analysis of relative use of available temperatures (compositional analysis) indicated a preference for the lowest available temperatures of 24 to 26 °C in both acclimation groups. These findings indicate that Z. flavescens can completely compensate AS and swimming ability to the elevated SST conditions, although T_pref remains near or below the current summer SST, suggesting other factors explain behavioral temperature preference.