Untitled - CNR

Marine research at CNRthe anaesthetic characteristics of Eugenol,the only anaesthetic that could be usedon fish destined for human consumption,we compared it with 2-Phenoxyethanol,which is considered an excellent anaestheticon fish, having a short biologicalhalf-life and very fast induction and recoverytimes as reported by the available bibliographicaldata [15, 16, 17, 18, 19, 20, 10,21]. In particular, to evaluate the anaestheticcharacteristics of 2-Phenoxyethanoland Eugenol during induction and recovery,these substances were administratedin increasing concentrations to farmed Europeansea bass and then making a directcomparison between them.2 Materials and Methods2.1 FishA total of 240 farmed European seabass (Dicentrarchus labrax) aged around 2years, weighing 223.3 ± 95.1 g (Mean ±SD) and measuring 24.2 ± 3.1 cm (Mean ±SD), were examined in this study. The fishcame from the off-shore fish farm “Hippocampus”(Villafranca Tirrena - Messina,Italy).2.2 Experimental designThe experiments required the use ofEugenol (ALDRICH, St. Louis, MO,USA) and 2-Phenoxyethanol (MERCK,Whitehouse Station, NJ, USA). Eugenoland 2-Phenoxyethanol were used in theform of 99% (v/v). From the initial solutionthe required amounts were mixedwith water from the tanks in order to obtainthe desired final concentrations. Thestudy was designed to include eight experimentaltrials (from I to VIII), one foreach concentration of the anaesthetics chosen.Four increasing concentrations of 2-Phenoxyethanol were used in trials I toIV (0.2, 0.3, 0.4 and 0.5 ml·l −1 respectively)and four increasing concentrationsof Eugenol were used in trials V to VIII(0.03, 0.06, 0.1 and 0.14 ml·l −1 respectively).These concentrations were selectedafter reference to other studies [23, 17,19, 24, 25]. The entire study was performedduring the month of July 2007.A diagram with a schematic representationof the experimental design is presentedin Figure 1. Each trial was carried outon the boat owned by the fish-farm “Hippocampus”and used for farming operations(feeding, fishing, maintenance of thefish cages). All the trials were carried outduring the routinely fishing operations onthe farm. For each trial were used 30fish. During each trial, a pen containingseabass was approached with the boat and30 fish were caught with a net. Ten ofthe thirty fish caught were randomly selectedand immersed in a tank (on the boat)containing 400 l of water and ice, in a ratioof 1:2. Following this, fish behaviourwas observed and the times of death wererecorded. In the meantime, the remainingtwenty sea bass were placed in another400 l tank, provided with a flow-throughsupply of aerated seawater at a temperatureof 24.3 ± 0.8°C and salinity of 36.3 ±0.78 ppt and were then anaesthetized. Thesea bass undergoing this study were carefullyobserved in order to note the characteristicsof anaesthesia induction; the datacollected are presented in a table on theanaesthetic stages based on the physiologicalresponses of the fish following administrationof the anaesthetics (Table 1). Afterhaving reached the maximum state ofanaesthesia, ten of the twenty fish wereplaced in the tank with water and ice which1943