Development in a warm future ocean may enhance performance in some species

• Acclimation to future warming may produce enhanced performance in some species.
• Aerobic performance is enhanced for anemonefish reared at elevated temperatures.
• Fish were longer, heavier and in better condition at + 3.0 °C than present-day.
• Partial increase in critical thermal maximum of fish reared at + 1.5 °C.

Understanding the capacity of organisms to cope with projected global warming through acclimation and adaptation is critical to predicting their likely future persistence. The vast majority of research on tropical species suggests they will be substantially negatively affected by future warming and have limited capacity to acclimate to changes. This study tested whether the spine cheek anemonefish, Premnas biaculeatus, has the capacity for developmental thermal acclimation of metabolic attributes and critical thermal maximum (CTmax) to increasing sea water temperature. Juveniles of P. biaculeatus exhibited high capacity for developmental thermal acclimation of aerobic physiology. Fish reared at + 1.5 °C and + 3.0 °C above present-day mean temperatures possessed enhanced performance across all testing temperatures (28.5 °C to 31.5 °C), i.e. overcompensation. Specifically, this occurred through increases in maximum oxygen consumption (MO2Maximum) that resulted in elevations in both net and factorial aerobic scope. In addition, fish reared at + 1.5 °C also exhibited a partial increase in critical thermal maximum (CTmax) by 0.5 °C, however no increase was observed in fish reared at + 3.0 °C. Fish reared at + 3.0 °C were significantly longer, heavier and in better condition than + 0.0 °C present-day fish, suggesting that alterations to aerobic physiology correspond to enhancement of growth and condition as would be predicted with the oxygen and capacity limited thermal tolerance hypothesis. These results indicate that the acclimation to future warming may produce overall enhanced performance in some species. It also suggests that the developmental acclimation ability varies substantially between species within the same family and a greater understanding of promoted or reduced acclimation capacity will be critically important to predicting the impacts of climate change on coral reef systems.