Finding the peak of dynamic oxygen uptake during fatiguing exercise in fish

Abstract

As fish approach fatigue at high water velocities in a critical swimming speed (U crit) test, their swimming mode and oxygen cascade typically move to an unsteady state because they adopt an unsteady, burst-andglide swimming mode despite a constant, imposed workload. However, conventional rate of oxygen uptake (_ M O2) sampling intervals (5-20 min) tend to smooth any dynamic fluctuations in active _ M O2 (_ M O2active) and thus likely underestimate the peak _ M O2active. Here, we used rainbow trout (Oncorhynchus mykiss) to explore the dynamic nature of _ M O2active near U crit using various sampling windows and an iterative algorithm. Compared with a conventional interval regression analysis of _ M O2active over a 10-min period, our new analytical approach generated a 23% higher peak _ M O2active. Therefore, we suggest that accounting for such dynamics in _ M O2active with this new analytical approach may lead to more accurate estimates of maximum _ M O2 in fishes.

Valid oxygen uptake measurements: using high r2 values with good intentions can bias upward the determination of standard metabolic rate

“…In such cases, the rolling regression algorithm proposed by Zhang et al . (2019) to measure maximum metabolic rate could be adapted for the determination of SMR. The algorithm examines the dynamic nature of active O 2 in a large volume respirometer when fish metabolic state is more likely to change during a long measurement period.…”

Inter-population differences in salinity tolerance of adult wild Sacramento splittail: osmoregulatory and metabolic responses to salinity

“…Metabolic rate was calculated and allometrically adjusted as described for RMR measurements. Metabolic rates were calculated for every 2 min interval of O 2 measurements performed during the one-hour recovery period; 2 min was the minimum interval that allowed for calculation of slope in O 2 over time with r 2 values ≥0.9 ( Hvas and Oppedal, 2019 ; Zhang et al ., 2019 ). Active metabolic rate was determined as the highest value recorded over 2 min during the 1-h recovery period after the metabolic challenge.…”

Analytical methods matter too: Establishing a framework for estimating maximum metabolic rate for fishes

“…Using simulated background respiration data, we tested the effectiveness of a signal-to-noise ratio analysis method in determining an appropriate regression window width to use in the analysis of MMR data (Zhang et al, 2019(Zhang et al, , 2020. This method leverages the low ratio of oxygen consumption signal relative to system noise detectable in a background respiration trace to inform the minimum window width that may be appropriate for that experimental system.…”

“…The standardization of experimental approaches for estimating MMR is improving as a growing number of studies outline the design and setup of associated respirometry experiments (Cech Jr. & Brauner, 2011;Chabot et al, 2016;Clark et al, 2013;Nelson, 2016;. However, the analytical process of actually estimating MMR from the experimental oxygen consumption data immediately following exhaustive exercise or air exposure-specifically, the statistical algorithm used to regress oxygen consumption over time-has not been systematically tested or standardized, despite recent recognition that these analytical choices affect MMR estimates (Little et al, 2020;Zhang et al, 2019Zhang et al, , 2020. Often, details concerning the analytical approach used to estimate MMR are not clearly reported, and when provided, there is usually little or no explanation as to why those specific methods were chosen.…”

“…Rolling regression is growing in popularity because the overlapping regression windows give an extremely high resolution that reduces the chance of missing the MMR window, and this method is simple to implement with common programming software such as Excel, R, and Labchart (Figure 1a) (Harianto et al, 2019;Zhang et al, 2019).…”