Methods matter: Considering locomotory mode and respirometry technique when estimating metabolic rates of fishes

Data for: Rummer JL, Binning SA, Roche DG, Johansen JL (2016) Methods matter: considering locomotory mode and respirometry technique when estimating metabolic rates of fishes. Conserv Physiol 4: doi:10.1093/conphys/cow008.

Data collected by JLR and JLJ. Please refer to the manuscript for data collection methods and statistical analyses. Metadata for the .csv data files are included in the ReadMe.txt file. For questions or to notify the authors if any errors are identified in the data, please contact the corresponding author (jodie.rummer@jcu.edu.au).

We estimated maximum metabolic rates (MMR) in four steady-swimming coral reef fishes – two body-caudal and two median-paired fin swimmers – using three different techniques. Differences between MMR estimates were not due to locomotory mode, but rather the method used to initiate maximum performance, with swimming respirometry resulting in the highest estimates.

Abstract:

Respirometry is frequently used to estimate metabolic rates and examine organismal responses to environmental change. Although a range of methodologies exists, it remains unclear whether differences in chamber design and exercise (type and duration) produce comparable results within individuals and whether the most appropriate method differs across taxa. We used a repeated-measures design to compare estimates of maximal and standard metabolic rates (MMR and SMR) in four coral reef fish species using the following three methods: (i) prolonged swimming in a traditional swimming respirometer; (ii) shortduration exhaustive chase with air exposure followed by resting respirometry; and (iii) short-duration exhaustive swimming in a circular chamber. We chose species that are steady/prolonged swimmers, using either a body–caudal fin or a median– paired fin swimming mode during routine swimming. Individual MMR estimates differed significantly depending on the method used. Swimming respirometry consistently provided the best (i.e. highest) estimate of MMR in all four species irrespective of swimming mode. Both short-duration protocols (exhaustive chase and swimming in a circular chamber) produced similar MMR estimates, which were up to 38% lower than those obtained during prolonged swimming. Furthermore, underestimates were not consistent across swimming modes or species, indicating that a general correction factor cannot be used. However, SMR estimates (upon recovery from both of the exhausting swimming methods) were consistent across both shortduration methods. Given the increasing use of metabolic data to assess organismal responses to environmental stressors, we recommend carefully considering respirometry protocols before experimentation. Specifically, results should not readily be compared across methods; discrepancies could result in misinterpretation of MMR and aerobic scope.