The effects of stress induced by cortisol administration on the repeatability of swimming performance tests in the European sea bass (Dicentrarchus labrax L.)

Abstract

The impact of stress induced by cortisol administration on the swimming performance of the European sea bass was tested measuring the fish recovery capability using a respirometer. The recovery test consisted of two exhaustive swimming exercises (U _crit) separated by a recovery period. Thirty-eight fish were subjected to this trial preceded or not (control group) by a cortisol (cortisol group) or saline (placebo) injection. For validation, the classical stress parameters (cortisol, glucose, lysozyme, Hct, Hb and RBCC) were monitored. During the recovery tests, only the cortisol group showed a significant reduction in the recovery capability that was interpreted as a sign of possible physiological impairment. Hct, Hb and RBCC did not show significant inter and intra-group differences, while cortisol and glucose increased as a response to fatigue in all the groups at the end of the trials. No immune (lysozyme) response was observed in control and placebo groups, while a reduction was evidenced in the cortisol group.

Keywords:

• cortisol
• injection
• U _crit
• recovery test
• glucose
• lysozyme
• haematocrit
• haemoglobin
• erythrocytes
• swimming performance

Acknowledgements

This study was supported by the SFOP EU funds, co-financed by the regional government of Puglia (Italy). The whole experimentation was carried out according to the guidelines of The European Commission. C2007 2525 (Use of animals for experimentation and other scientific purposes, 18 June 2007; www.eur-lex.eurpa.eu). The authors are grateful to Dr Zupa Walter for his contribution to the final version of the manuscript.