Stress-related physiological and histological responses of tambaqui (Colossoma macropomum) to transportation in water with tea tree and clove essential oil anesthetics

The present study evaluated the effects of the combination of tea tree and clove oils in comparison with salt added to water on the stress indicators in tambaqui subjected to two transportation experiments: one lasting 15 h and another 36 h. The fish were divided into two treatment groups and then transported in plastic bags (195 g L−1; 20 replicates per treatment) containing previously prepared water. In the group with 2 oils (MEUG), the fish were transported in water added with 10.4 mg L−1 of anesthetic solution of tea tree and clove oils while in salt (SALT) at 0.8% was added. The basal group comprised fish that were not subjected to transportation. The efficacy of these phytotherapics was verified by analyzing biochemical, hematological and histological indicators after transportation and 96 h of recovery. The levels of cortisol, glucose and plasma lactate increased after transportation in comparison with the basal ones. The glycemic values of the MEUG treatment were inferior to the SALT treatment, regardless transportation time. The same occurred for the lactate, only in the 15-h experiment. The hepatic glycogen levels were higher in the MEUG treatment. No alterations were observed in the ions (sodium, chloride, potassium) regardless treatment and transportation time. The hemoglobin concentration increased in the SALT treatment after transportations for 15 h and 36 h. The gills did not undergo deleterious morphophysiological alterations. Except for the hepatic glycogen in the SALT treatment, all parameters were similar to the basal ones after recovery for 96 h. The indicators showed primary and secondary responses to stress, with more favorable results for the 15 h and 36 h transportations using the combined essential oils of tea tree and clove at 10.4 mg L−1 for sedation. •This study evaluated the effect of tea tree essential oil in association with clove oil in fish transport.•The combination of these oils improved water quality and reduced plasma levels of glucose, lactate and prevented the loss of ions.•The use of this oil softens the stress of transporting fish.