Effects of Exercise Conditioning on Stress Responses and Recovery in Cultured and Wild Young-of-the-Year Striped Bass, Morone saxatilis

Abstract

Exercise conditioning at 1.2–2.4 body lengths∙s−1 for 60 d significantly improved physiological responses to and decreased recovery time from capture, net confinement, and crowding (collectively, "handling") stress in cultured and wild young-of-the-year striped bass, Morone saxatilis. Plasma cortisol increased dramatically 0.5 h after acute handling in all treatments. However, cortisol returned to prestress levels 4 h after handling in exercise-conditioned cultured and wild fish but not in the respective unexercised fish. Handling stress in all groups of fish also resulted in hyperlacticemia. Faster clearance of plasma lactate following handling stress was shown in exercise-conditioned cultured and wild striped bass compared with unexercised fish. Handling stress resulted in a rapid hemoconcentration as indicated by increases in osmolality and hematocrit levels. Osmotic imbalance was less severe in exercise-conditioned cultured and wild fish than in unexercised fish. These improved stress responses and enhanced recovery in young-of-the-year striped bass should result in increased survival of both cultured and wild fish after transport and stocking into the natural environment.