Plasma cortisol and secondary stress responses of cultured red drum ( Sciaenops ocellatus) to several transportation procedures

Abstract

Transportation procedures induced rapid elevations in plasma cortisol and glucose concentrations (100–160 ng/ml and 60–140 mg/100 ml, respectively) within 15–30 min of capture and loading in cultured juvenile red drum. The elevations were transient and plasma levels of cortisol returned to baseline levels during the 5.5 h transport, suggesting that capture and loading are the most traumatic procedures. Plasma glucose concentrations had returned to baseline values within 1–2 days of transport. Plasma osmolality increased during transportation in 32 ppt seawater and decreased during transport in 4 ppt seawater. Survival ranged from 96 to 100%, indicating that despite the trauma associated with initial transport procedures, juvenile red drum can be transported successfully in seawater or low salinity seawater. Anesthesia with MS-222 (80 mg/l) prior to capture, coupled with the use of sedating doses (5 and 25 mg/l MS-222) in the transport tanks, did not decrease the magnitude of the stress responses. On the contrary, the corticosteroid stress response was augmented in fish transported in 25 mg/l MS-222. Laboratory tests showed that long-term (30–90 min) exposure to sedating doses of the anesthetic caused a dose-dependent increase in plasma cortisol levels, whereas anesthetization of red drum with MS-222 prior to capture and transport in anesthetic-free seawater markedly reduced the plasma corticosteroid response after capture/loading and at the end of transport. Plasma glucose levels and osmolality were also lower in those fish anesthetized prior to capture. These results suggest that acute exposure to immobilizing doses of an anesthetic, MS-222, is an effective method of reducing endocrine and metabolic disturbances during transportation of red drum.