Essential oils as anaesthetics and sedatives in native Brazilian fish, with a special emphasis on Colossoma macropomum: A review

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.