Metabolic Cost of Acute Physical Stress in Juvenile Steelhead

Juvenile steelhead Salmo gairdneri were subjected to three consecutive 2-min disturbances, separated by 0.5-h intervals, and then forced to swim at 0.5 body length/s for 1 h in a modified Blazka respirometer. Mean oxygen consumption (±SE) was 223 ± 19 mg˙kg−1˙h−1 in the stressed fish and 101 ± 9.7 in unstressed fish. There was no significant correlation between oxygen consumption and fish weight or water temperature within the ranges used (40–150 g and 8–11°C, respectively). Elevated plasma cortisol levels and oxygen consumption rates in stressed fish were positively correlated (r = 0.76). An acute physical stress may adversely affect fish by reducing, by about one-quarter, the energy available for other activities within the scope for activity of the fish.