Aerobic scope measurements of fishes in an era of climate change: respirometry, relevance and recommendations

Measurements of aerobic scope [the difference between minimum and maximum oxygen consumption rate ((M) over dot(O2,min) and (M) over dot(O2,max), respectively)] are increasing in prevalence as a tool to address questions relating to fish ecology and the effects of climate change. However, there are underlying issues regarding the array of methods used to measure aerobic scope across studies and species. In an attempt to enhance quality control before the diversity of issues becomes too great to remedy, this paper outlines common techniques and pitfalls associated with measurements of (M) over dot(O2,min), (M) over dot(O2,max) and aerobic scope across species and under different experimental conditions. Additionally, we provide a brief critique of the oxygen-and capacity-limited thermal tolerance (OCLTT) hypothesis, a concept that is intricately dependent on aerobic scope measurements and is spreading wildly throughout the literature despite little evidence for its general applicability. It is the intention of this paper to encourage transparency and accuracy in future studies that measure the aerobic metabolism of fishes, and to highlight the fundamental issues with assuming broad relevance of the OCLTT hypothesis.