EFFECTS OF EXERCISE CONDITIONING ON STRESS RESPONSES AND RECOVERY IN CULTURED AND WILD YOUNG-OF-THE-YEAR STRIPED BASS, MORONE-SAXATILIS

Exercise conditioning at 1.2-2.4 body lengths.s(-1) for 60 d significa ntly improved physiological responses to and decreased recovery time f rom capture, net confinement, and crowding (collectively, ''handling'' ) stress in cultured and wild young-of-the-year striped bass, Morone s axatilis. Plasma cortisol increased dramatically 0.5 h after acute han dling in all treatments. However, cortisol returned to prestress level s 4 h after handling in exercise-conditioned cultured and wild fish bu t not in the respective unexercised fish. Handling stress in all group s of fish also resulted in hyperlacticemia. Faster clearance of plasma lactate following handling stress was shown in exercise-conditioned c ultured and wild striped bass compared with unexercised fish. Handling stress resulted in a rapid hemoconcentration as indicated by increase s in osmolality and hematocrit levels. Osmotic imbalance was less seve re in exercise-conditioned cultured and wild fish than in unexercised fish. These improved stress responses and enhanced recovery in young-o f-the-year striped bass should result in increased survival of both cu ltured and wild fish after transport and stocking into the natural env ironment.