Abstract:

This study investigated some aspects of stress research, including, also, the effects of chemical anaesthesia, in two important species for diversification in aquaculture, blackspot seabream, Pagellus bogaraveo and greater amberjack, Seriola dumerilii. The first part of the research (trial 1 and 2) was designed to determine the efficacy of clove oil as an anaesthetic alternative to MS-222. In trial 1, the minimum concentration of anaesthetic producing the total loss of muscular tone within 3 min, and recovery within 10 min, was determined. The obtained results showed that MS-222 and clove oil were effective as anaesthetics for juveniles of blackspot sea-bream and greater amberjack at concentrations of 40 and 100 mg L-1, respectively. The aim of trial 2 was to assess the side-effects of both anaesthetics on greater amberjack juveniles by monitoring serum cortisol and glucose levels, and haematocrit values. No significant differences between anaesthetics were found for most of the measured physiological variables. The second part of research (trial 3) was designed to establish the ability of anaesthesia to mitigate stress responses blocking activation of the HPI axis associated to handling stress. In this trial, the stress responses to handling of adult blackspot sea-bream anaesthetised with either anaesthetics were compared to those of unanaesthetised fish used as controls. Serum cortisol and glucose concentrations were used as stress indicators. Both anaesthetics were unable to block activation of the HPI axis that occurs as a consequence of handling stress in blackspot sea-bream, although anaesthesia with both anaesthetics proved to be effective in reducing the duration of stress response.