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Several routine aquaculture practices, such as densification, handling and transport, are considered potential stressors and can cause physiological alterations that compromise the animals' welfare and survival. Studies of plant‐based anaesthetic products have become a trend worldwide, mainly due to their potential uses and the variety of species that can provide suitable substances. In Brazil, the use of essential oils (EO) in fish farming for use in sedation and anaesthesia has already been explored. However, despite the excellent biological activity of the EO, as a result of their main compounds or due to the synergy between the active compounds, it is also necessary to investigate the adverse effects that they can cause and accordingly establish the appropriate dosage for their use. Sedative and anaesthetic properties of the EOs of at least 30 plant species have been described for native fish species reared in Brazil such as Colossoma macropomum, Rhamdia quelen, Brycon amazonicus, Lophiosilurus alexandri, Piaractus mesopotamicus, P. mesopotamicus × C. macropomum, Pseudoplatystoma reticulatum and Serrasalmus rhombeus. However, the mechanisms of action of the EOs need to be elucidated, as well as the undesirable side effects they may cause in fish. This review presents information on the use of EOs as anaesthetics and sedatives in native fish species farmed in Brazil, with emphasis on C. macropomum and, as a future perspective, the application of new technologies is emphasized to potentialize the biological activities of EOs, thus contributing with environment‐friendly natural alternatives for the promotion of sustainable aquaculture. [ABSTRACT FROM AUTHOR]

This study evaluated the effect of short‐term baths with the essential oils (EOs) of Lippia sidoides, Ocimum gratissimum and Zingiber officinale on the survival, haematological, biochemical and histopathological parameters of native fish tambaqui (Colossoma macropomum), challenged with Aeromonas hydrophila. After challenge, the fish infected with A. hydrophila received therapeutic baths of 60 min, for five consecutive days. Treatments were as follows: challenged and not treated; challenged and treated with 10 mg L−1 of gentamicin; challenged and treated with EO of L. sidoides (2.5 and 5.0 mg L−1); challenged and treated with EO of O. gratissimum (5.0 and 10.0 mg L−1); challenged and treated with Z. officinale EO (5.0 and 10.0 mg L−1). The highest survival rates were 89.5% (fish treated with 5.0 mg L−1 of O. gratissimum EO) and 75.0% (fish treated with 5.0 mg L−1 of L. sidoides EO). Reductions in the haematocrit percentage, haemoglobin and erythrocyte number were observed in fish treated with L. sidoides and Z. officinale EOs compared with control fish. Mild to moderate damage to the liver tissue of fish after challenge and EO treatments were observed. It is suggested that baths containing O. gratissimum and L. sidoides EOs consist in a viable treatment to increase survival rates of C. macropomum infected with A. hydrophila. [ABSTRACT FROM AUTHOR]

The aim of this study was to evaluate the antimicrobial activity of Lippia sidoides, Ocimum gratissimum and Zingiber officinale's essential oils against Aeromonas spp. isolates from Colossoma macropomum, and to determine their chemical composition. Essential oils were obtained through hydrodistillation and their chemical composition analyzed using gas chromatography coupled to mass spectrometry. The antimicrobial activity of the oils was evaluated by minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). The major compounds were thymol (76.6%), p-cymene (6.3%) and (E)- β-caryophyllene (5.0%) in L. sidoides; eugenol (43.3%), 1,8-cineole (28.2%) and β-selinene (5.5%) in O. gratissimum; and geranial (23.2%), neral (16.7%) and 1,8-cineole (15.8%) in Z. officinale. All the essential oils evaluated showed bactericidal action against isolates of Aeromonas spp., with MIC and MBC ranging from 625 to 5,000 μg mL−1. We highlight the L. sidoides oil with the best antimicrobial activity (MIC and MBC ranging from 625 to 1,250 μg mL−1). [ABSTRACT FROM AUTHOR]