Data from: Effects of hypoxia and ocean acidification on the upper thermal niche boundaries of coral reef fishes

Rising ocean temperatures are predicted to cause a poleward shift in the
distribution of marine fishes occupying the extent of latitudes tolerable
within their thermal range boundaries. A prevailing theory suggests that
the upper thermal limits of fishes are constrained by hypoxia and ocean
acidification. However, some eurythermal fish species do not conform to
this theory, and maintain their upper thermal limits in hypoxia. Here we
determine if the same is true for stenothermal species. In three coral
reef fish species we tested the effect of hypoxia on upper thermal limits,
measured as critical thermal maximum (CTmax). In one of these species we
also quantified the effect of hypoxia on oxygen supply capacity, measured
as aerobic scope (AS). In this species we also tested the effect of
elevated CO2 (simulated ocean acidification) on the hypoxia sensitivity of
CTmax. We found that CTmax was unaffected by progressive hypoxia down to
approximately 35 mmHg, despite a substantial hypoxia-induced reduction in
AS. Below approximately 35 mmHg, CTmax declined sharply with water oxygen
tension (PwO2). Furthermore, the hypoxia sensitivity of CTmax was
unaffected by elevated CO2. Our findings show that moderate hypoxia and
ocean acidification do not constrain the upper thermal limits of these
tropical, stenothermal fishes.