Acclimation Temperature Influences Cortisol and Glucose Concentrations in Stressed Channel Catfish

Abstract

Basal concentrations of plasma cortisol (near 50 ng/ml) and plasma glucose (near 0.50 mg/ml) were significantly greater in yearling channel catfish (Ictalurus punctatus) acclimated to 10 C than in fish adapted to 20 or 30 C; the latter groups had similar basal levels of cortisol (near 25 ng/ml) and glucose (near 0.30 mg/ml). Fish at 10 C had a slower and less marked increase in cortisol and glucose over minutes, hours, and days in response to the stress of severe confinement than fish at 20 or 30 C which were again similar. No mortality occurred in the fish stressed at 10 C during 3 days of confinement, while 89% died in the 20 C group by day 3 and all fish at 30 C were dead by day 2. Glucose concentrations initially rose more slowly than those of cortisol, but continued to increase between 3 and 12 hours after confinement. Also, glucose returned to near basal levels in dying fish while cortisol was at its highest then. Channel catfish, even at warm temperatures, have a slower and less extensive cortisol response to stress, taking 3 days to reach 225 ng/ml, than other fish that have been investigated.