The anaesthetic efficacy of Eucalyptus globulus essential oil on silver catfish (Rhamdia quelen)

Aquaculture handling requires fast anaesthesia, assuming an action-time within 3 min and a recovery time of <5 min. This study aimed to determine the lowest effective concentration (LEC) of eucalyptus (Eucalyptus globulus) essential oil (EEO) administered to Rhamdia quelen and its anaesthetic effects. Analysis of EEO chemical profile showed 1,8-cineole as the main component. Two assays were then carried out. In the first, four concentrations were tested (600, 650, 700 and 750 mu l L-1). EEO was found to be an effective anaesthetic in R. quelen with LEC of 700 mu l L-1. During this assay, no fish mortality occurred. The second assay evaluated stress. Fish were divided into three groups: control (baseline values, without anaesthetic); eugenol (50 mg L-1) and EEO (700 mu l L-1). In this assay, EEO also inhibited the primary stress response. While cortisol did not increase in the EEO regime, plasma glucose and lactate levels did increase in blood. Meanwhile, eugenol kept all stress indicators equal to those of the control group. Therefore, although EEO has suitable anaesthetic characteristics, it should be used with caution, as it does not prevent changes in plasma glucose and lactate for R. quelen.

Automated summary

The study determined the lowest effective concentration of eucalyptus essential oil as an anaesthetic for Rhamdia quelen. While it proved to be effective, caution is advised as it did not prevent changes in plasma glucose and lactate levels.