Thus, two different studies were conducted using eugenol as an anesthetic for severe discus Heros severus. Both studies were conducted in Tropical Fish Laboratory of the School of Coastal Studies Institute of Fisheries Engineering, Federal University of Pará, Campus de Bragança. In the first study aimed to analyze the efficiency of eugenol as an anesthetic for two size classes, fingerlings and adult severe discus and find what the most effective dose in time of induction and recovery of anesthesia. Were used 120 individuals of H. severus, fingerlings (n=60) and adults (n=60). The fingerlings were selected randomly in homogeneous sizes and transferred to six tanks of 60 L, as adults for six aquariums 200L, both at 10 copies per aquarium stocking density. We conducted the experiments in a completely randomized design with six treatments, eugenol concentrations (50; 75; 100; 125; 150 and 175 Mg L-1) and 10 repetitions, and the fish the experimental unit. Based on the findings is recommended for fry concentration of 50 mg L-1 to perform handlings short or long term and for adults, it is recommended that the concentration of 50mg L-1 for short procedures duration and 75 mgL-1 for long procedures. In the second study aimed to evaluate the physiological responses of acará severo adults anesthetized with the ideal concentration of eugenol found in the previous experiment. To perform the assay was used a total of 60 adult severe discus. The fish were placed individually in 60 60L aquariums containing 45L of water. We used a completely randomized design in a factorial 3 x 4 with five repetitions, and the fish the experimental unit. To verify the occurrence of eugenol influence on the physiological and hematological parameters of banded cichlid, was collected the blood of fish subjected to three diferentes protocols procedures anaesthetized (fish exposed to 75 mg L-1 of eugenol during 133 s); simulated anesthesia (fish subjected to a sumulation of anesthetic bath, also for 133 s, with only water and without adding the anesthetic); and control (fish kept in the aquarium without handing and exposure to anesthetic). For each procedure, there were four blood samplings at different times: 0 (immediately after procedure), 6, 12 and 24 h. The withdrawal of the blood sample was taken by puncture from the flow vessel with the held of needles and syringes 1 ml pre-moistened with EDTA 10%. Then were proceeded to carry out folloying analyzes: glucose, hematocrit, (Ht), total protein (Tp), hemoglobin (Hb), number of erytrocytes (Er), mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), mean corpuscular hemoglobin concentration (MCHC), triglycerides (TGR), and cholesterol (COL). The banded cichlid adult exposure to anesthesia with eugenol in the ideal concentration of 75 mg L-1 by 133 seconds was enough to cause changes in the values of variables, glucose, Ht, Pt, Hb, Er,
MCV, MCH, MCHC, COL and TRI. The results from the two studies show that eugenol was effective in inducing fry and adult severe discus to deep anesthesia stage stage in all tested concentrations and the concentration considered ideal for anesthesia of adults was enough to cause changes in the variables analyzed, triggering physiological responses characteristics of stress.
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