The energetic response to handling stress in juvenile coho salmon

The metabolic cost of stress increased with the severity of handling in juvenile coho salmon Oncorhynchus kisutch examined via respirometry. Stressed fish had rates of oxygen consumption 39-98% higher than controls. Elevation in oxygen consumption was largely eliminated within 1 h after stress. Oxygen consumption was significantly correlated to both plasma cortisol and lactate concentration in response to a moderate stressor, but no correlation was found after more severe stressors. Fish given exogenous cortisol did not experience an increase in oxygen consumption, so cortisol alone is unlikely to have a major effect on metabolic rate. Whole-body lactate concentration was significantly elevated following stress, reaching levels almost 500% higher than controls. We suggest that metabolism associated with exercise or hypoxia is the dominant source of elevated oxygen consumption following handling.