The determination of standard metabolic rate in fishes

Abstract

This review and data analysis outline how fish biologists should most reliably estimate the minimal amount of oxygen needed by a fish to support its aerobic metabolic rate (termed standard metabolic rate; SMR). By reviewing key literature, it explains the theory, terminology and challenges underlying SMR measurements in fishes, which are almost always made using respirometry (which measures oxygen uptake,ṀO 2 ). Then, the practical difficulties of measuring SMR when activity of the fish is not quantitatively evaluated are comprehensively explored using 85 examples ofṀO 2 data from different fishes and one crustacean, an analysis that goes well beyond any previous attempt. The main objective was to compare eight methods to estimate SMR. The methods were: average of the lowest 10 values (low10) and average of the 10% lowestṀO 2 values, after removing the five lowest ones as outliers (low10%), mean of the lowest normal distribution (MLND) and quantiles that assign from 10 to 30% of the data below SMR (q 0⋅1 , q 0⋅15 , q 0⋅2 , q 0⋅25 and q 0⋅3 ). The eight methods yielded significantly different SMR estimates, as expected. While the differences were small when the variability was low amongst theṀO 2 values, they were important (>20%) for several cases. The degree of agreement between the methods was related to the c.v. of the observations that were classified into the lowest normal distribution, the c.v. MLND (C.V. MLND ). When this indicator was low (≤5⋅4), it was advantageous to use the MLND, otherwise, one of the q 0⋅2 or q 0⋅25 should be used. The second objective was to assess if the data recorded during the initial recovery period in the respirometer should be included or excluded, and the recommendation is to exclude them. The final objective was to determine the minimal duration of experiments aiming to estimate SMR. The results show that 12 h is insufficient but 24 h is adequate. A list of basic recommendations for practitioners who use respirometry to measure SMR in fishes is provided.

To boldly gulp: standard metabolic rate and boldness have context-dependent influences on risk-taking to breathe air in a catfish

“…The quantile splits the dataset into the time to resume air breathing after a simulated predator attack q smallest and the 1−q largest values, where q is a proportion chosen by the experimenter. Here, q was fixed at 0.12 such that 12% of values fell below true SMR (Chabot et al, 2016). All measures of RMR were considered for each individual, both in normoxia and hypoxia, hence four measures per hour over 48 h, or 192 measures.…”

“…The SMR was estimated by the quantile method (Dupont-Prinet et al, 2010;Chabot et al, 2016). This assumes that a certain proportion of all measured rates of RMR are below true SMR because of temporal variability and possible measurement errors.…”

Exploring key issues of aerobic scope interpretation in ectotherms: absolute versus factorial

“…As a caveat to these recommendations, we caution that the mathematical derivations of aerobic scope will not compensate for poorly collected data and care should be placed on using best practice respirometry techniques and obtaining robust datasets to be used for aerobic scope calculations (Chabot et al 2016;Clark et al 2013;Steffensen 1989;Svendsen et al 2016). This is true in all cases but is particularly important when the goal is to quantify variation among individuals or treatments.…”

Effects of Harmful Algal Blooms on Fish: Insights from Prymnesium parvum

“…To ensure the overall precision of the measurements, any MO 2 determination with a coefficient of determination (r 2 ) below 0.95 were discarded prior to analysis [26]. The standard metabolic rate (SMR), defined as the MO 2 of a resting and non-digesting fish [22,27], was determined for all pre-exposure measurements by fitting a double normal distribution to the measurements [28,29], obtaining the average of the lower distribution as a measure of SMR. The other, higher distribution represents a measure of unwanted routine metabolic rate [27] caused by spontaneous activity in MO 2 measurements [29], and thus discarded.…”