The physiological responses of the rainbow trout to strenuous exercise: interactions of water hardness and environmental acidity

Abstract

Cannulated adult rainbow trout were subjected to 6 min of exercise stress in 4 different water conditions: hard water (.simeq. 140 mg/l as CaCO3), control pH (.simeq. 7.5); artificial soft water (.simeq. 14 mg/l), control pH; hard water, acid pH (.simeq. 4.4); and artificial soft water, acid pH. Physiological changes and postexercise mortalities were monitored over a 12 h recovery period. The physiological responses to exercise stress were qualitatively similar in all treatments and are discussed in detail. At control pH, water hardness had minimal influence on the magnitude of physiological response and postexercise mortality. When fish were exercised in hard water at acid pH, the symptoms of postexercise acidosis were actually ameliorated slightly and there was no increase in mortality. Acid exposure in soft water greatly exacerbated most of the postexercise disturbances and caused a doubling of mortality.