Plasma Cortisol and Secondary Stress Responses of Red Drum to Handling, Transport, Rearing Density, and a Disease Outbreak

Abstract

Abstract The effects of some common fish culture procedures on the biochemical stress responses of juvenile red drum (Sciaenops ocellatus) were examined in the present study. Plasma cortisol, glucose, and osmolality were measured in cultured red drum subjected to capture and handling, transportation, an outbreak of disease, and different rearing densities. Capture and handling elicited rapid, marked elevations of plasma cortisol and glucose in the fish. The responses were transient, however, and the plasma concentrations returned to initial values 1 d after handling. Similarly, transportation of red drum induced rapid but transient plasma cortisol, glucose, and osmolality responses and caused no mortality. An outbreak of disease evoked cortisol, glucose, and osmolality stress responses in red drum. As the disease progressed, the plasma cortisol and osmolality responses became more pronounced. Fish reared at different densities had similar plasma glucose levels. Cortisol titers were temporarily elevated in fish held at the two higher densities (initially 10.5 and 18.4 g/L), but after 48 d the concentrations were at control values. The results of these studies with cultured red drum are compared to previous findings with different species. Methods to assess the effects of stressors and to reduce biochemical stress responses in cultured fish are also discussed.