The effect of acute temperature increases on the cardiorespiratory performance of resting and swimming sockeye salmon (Oncorhynchus nerka)

Abstract

SUMMARYThe mechanism underlying the decrease in aerobic scope in fish at warm temperatures is not fully understood and is the focus of this research. Our study examined oxygen uptake and delivery in resting, swimming and recovering sockeye salmon while water temperature was acutely increased from 15°C to 24°C in 2°C h -1 increments. Fish swam at a constant speed during the temperature change. By simultaneously measuring oxygen consumption (M O2 ), cardiac output (Q) and the blood oxygen status of arterial and venous blood, we were able to determine where in the oxygen cascade a limitation appeared when fish stopped sustained swimming as temperature increased. High temperature fatigue of swimming sockeye salmon was not a result of a failure of either oxygen delivery to the gills or oxygen diffusion at the gills because oxygen partial pressure (P O2 ) and oxygen content (C O2 ) in arterial blood did not decrease with increasing temperature, as would be predicted for such limitations. Instead, arterial oxygen delivery (Ta O2 ) was initially hampered due to a failure to adequately increase Q with increasing temperature. Subsequently, lactate appeared in the blood and venous P O2 remained constant.

Atlantic salmon show capability for cardiac acclimation to warm temperatures

“…Still, further research would be valuable. Although cardiac function is emerging as a particularly important in determining the upper thermal tolerance of a variety aquatic animals [7][8][9][10][11][12] , many other physiological factors are involved with the overall thermal plasticity of an ectothermic organism.…”

“…In a variety of fish and invertebrate species, cardiac function has been implicated as a limiting factor for upper temperature tolerance [7][8][9][10] , as indicated by their Arrhenius Breakpoint Temperature (T AB ) [9][10][11][12] . This is because as the rate of oxygen consumption increases exponentially with temperature, so does the heart rate (f H ).…”

“…This is because as the rate of oxygen consumption increases exponentially with temperature, so does the heart rate (f H ). Moreover, maximum heart rate (f Hmax ) in fishes ceases to increase at temperatures just beyond T opt , which then puts a limit on the amount of oxygen that can be supplied to tissues above the routine needs 4,7,8 . Thus, for fishes in vivo (when swimming maximally) and in vitro (pharmacologically stimulated), the rate transition temperatures T AB and T QB (when Q 10 decreases abruptly) for f Hmax have been specifically associated with T opt 11,12 .…”

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

“…In fact, for many fish species from temperate to tropical systems, FAS often decreases over the entire temperature range experienced by a species evaluated whereas AAS has been reported to display varying patterns from more or less bell-shaped to continuously increasing or remaining stable (e.g. Clark et al 2011;Healy and Schulte 2012;Norin et al 2014;Poletto et al 2017;Steinhausen et al 2008;Tirsgaard et al 2015).…”

Electrical and Contractile Properties of the Heart Ventricle in Response to Ambient Temperature Changes in Frog Rana temporaria

“…(1)(2)(3)(4) Ectothermic animals inhabiting regions with a temperate climate have to compensate for temperature changes in order to cope with the seasonal thermal variations. It is known that ectothermic vertebrate hearts are highly sensitive to temperature effects.…”