Oxygen Consumption and Swimming Performance in Hypoxia-Acclimated Rainbow Trout Salmo Gairdneri

Swimming performance and oxygen consumption of normoxic (control) and hypoxia-acclimated rainbow trout, Salmo gairdneri Richardson, were monitored at >145, 60 and 40mmHg.

Maximum swimming velocity at 40 mmHg was reduced from >54·8cms⁻¹ to 41·4cms⁻¹ in controls and to 40·6cms⁻¹ in hypoxia-acclimated fish.

Normoxic oxygen consumption of control fish ranged from 97·5mg O₂ kg⁻¹ h⁻¹ (5·5cms’¹) to 318-5mg O₂ kg⁻¹ h⁻¹ (54·8cms⁻¹) and did not differ significantly from that of hypoxia-acclimated fish in normoxia.

Reduction of ambient from normoxia to 60 mmHg or 40 mmHg did not significantly change oxygen consumption in control animals, although no fish (control or hypoxia acclimated) completed swimming trials at 54·8 cms⁻¹ in 40mmHg.

Oxygen consumption of hypoxia-acclimated fish at 5·5cms⁻¹ and 40 mmHg was significantly higher than oxygen uptake in normoxia at the same speed. This relative increase was not maintained, however, as oxygen consumption at higher swimming speeds was similar to that in normoxia.

Blood studies showed that hypoxia-acclimated fish had lower ATP concentrations and P50 values. While these factors may increase the blood oxygen loading capacity, the change is apparently not enough markedly to improve swimming performance or oxygen consumption in hypoxia and/or exercise.