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 (<i>U</i>_crit) test, their swimming mode and oxygen cascade typically move to an unsteady state because they adopt an unsteady, burst-and-glide swimming mode despite a constant, imposed workload. However, conventional rate of oxygen uptake (<i>Ṁ</i>_O₂ ) sampling intervals (5-20 min) tend to smooth any dynamic fluctuations in active <i>Ṁ</i>_O₂ (<i>Ṁ</i>_O₂active) and thus likely underestimate the peak <i>Ṁ</i>_O₂active Here, we used rainbow trout (<i>Oncorhynchus mykiss</i>) to explore the dynamic nature of <i>Ṁ</i>_O₂active near <i>U</i>_crit using various sampling windows and an iterative algorithm. Compared with a conventional interval regression analysis of <i>Ṁ</i>_O₂active over a 10-min period, our new analytical approach generated a 23% higher peak <i>Ṁ</i>_O₂active Therefore, we suggest that accounting for such dynamics in <i>Ṁ</i>_O₂active with this new analytical approach may lead to more accurate estimates of maximum <i>Ṁ</i>_O₂ in fishes.