The in vitro blood-O(2) affinity of triploid rainbow trout Oncorhynchus mykiss at different temperatures and CO(2) tensions.

Blood-O(2) affinity, Hill number and predicted arterial-O(2) saturation did not differ between diploid (2N) and triploid (3N) rainbow trout Oncorhynchus mykiss blood when compared under various temperature and CO(2) partial pressure combinations. These results suggest that reduced hypoxia and warm-water tolerance and aerobic capacity of 3N fishes are not due to altered blood-O(2) affinity. Further investigation into O(2) transport-diffusion capacity and intracellular pH within 3N fishes may further unravel the mechanisms behind reduced 3N tolerance of suboptimal environments.

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

The 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 degrees C to 24 degrees C in 2 degrees C h(-1) increments. Fish swam at a constant speed during the temperature change. By simultaneously measuring oxygen consumption (M(O(2))), 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(O(2))) and oxygen content (C(O(2))) in arterial blood did not decrease with increasing temperature, as would be predicted for such limitations. Instead, arterial oxygen delivery (Ta(O(2))) was initially hampered due to a failure to adequately increase Q with increasing temperature. Subsequently, lactate appeared in the blood and venous P(O(2)) remained constant.