Assessment of effective dose of new herbal anesthetics in two marine aquaculture species: Dicentrarchus labrax and Argyrosomus regius

Abstract

In this study, the anesthetic effect of two herbal oils extracted from oregano (Origanum sp.) and eucalyptus (Eucalyptus sp.) plants was evaluated. Two marine aquaculture species were used: European sea bass (Dicentrarchus labrax) of 90.91 +/- 2.46 g and meagre (Argyrosomus regius) of 127.43 +/- 3.07 g. The oil chemical composition was analyzed. The main components were carvacrol for oregano oil and 1,8-cineol for eucalyptus oil. Three doses were analyzed for each anesthetic on both species to determine the optimal dose. Clove oil, an anesthetic commercially used in the industry, was used as control one. Results pointed out that neither anesthetics caused side effects or mortality on any of the two species and that effectiveness of oregano oil was higher than that of eucalyptus oil and similar or even higher than that of clove oil depending on the species. Their optimal doses were 50 and 75 mu L . L-1 of oregano oil for meagre and sea bass, respectively, and 300 mu L . L-1 of eucalyptus oil for both species. The times for oregano oil were 49 s and 40 s for sedation stage and 3.51 min and 6.05 min for recovery stage on European sea bass and meagre, respectively. The times for Eucalyptus oil were longer. Overall, these results introduce oregano oil as a good alternative to clove oil and opens up the possibility of other plant based oils to be tested and their effectiveness as anesthetics to be proved.