THE PHYSIOLOGICAL-RESPONSE OF THE TURBOT TO MULTIPLE NET CONFINEMENTS

The effects of multiple net confinements on the physiological stress r esponse of the turbot (Scophthalmus maximus L.) were investigated. To allow for repeated blood sampling from individuals, fish were cannulat ed in the afferent branchial artery and were exposed to multiple 9 min net confinement episodes separated by either 4 h or 24 h. In fish str essed twice 4 h apart cumulative effects in plasma cortisol, glucose a nd free fatty acid concentrations were evident after the second handli ng stress. Although plasma Na+ and Cl- concentrations were not increas ed further by the second net confinement, the elevation in plasma conc entrations were more sustained compared to turbot handled only once. I n a second experiment where turbot were net confined five times, with a 24 h recovery period between each net confinement episode, there was no evidence of any physiological accommodation with repeated exposure s. For most circulatory parameters, there was also no evidence of any cumulative effect apparent. Plasma glucose concentrations were, howeve r, elevated to a significantly higher degree with repeated net confine ments. Although turbot were tolerant to the handling procedures, with no mortalities recorded, episodes of multiple handling of this species should be separated by at least 24 h if cumulative physiological. dis turbances are to be avoided. The significance of cumulative increases in plasma glucose concentrations is discussed.