THE ENERGETIC RESPONSE TO HANDLING STRESS IN JUVENILE COHO SALMON

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