Effects of abrupt cold shock on stress responses and recovery in brown trout exhausted by swimming

To simulate swimming in a trawl, age 3 year brown trout Sahno trutta (L.) were made to swim against a flow of 0.5 ms(-1) for 60 min. To simulate cold shock, similar to placing them in a chilling tank, the fish were kept for 10 min in a tank containing ice and water. To simulate the combined stressors, the fish were first made to swim followed by a cold shock. The fish were in a comatose state 10 min after cold shock and combined stressors but conscious after swimming only. All the fish survived until the end of the studied recovery period (maximum 24h). Cold shock after swimming (combined stressors v. swimming only) did not produce higher blood cortisol, lactate or glucose concentrations 10 min after the treatment. The effect of cold shock, however, was evident in the delayed start of recovery in cortisol and glucose concentrations. All the stress indicators used decreased to the levels for undisturbed fish within 24 h, except in the case of glucose after the combined stressors. (C) 2004 The Fisheries Society of the British Isles.