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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]

The objective of this study is to identify the economic–financial viability, attractiveness potential, and investment risks of tambaqui farming in the state of Amazonas, Brazil. Tambaqui is the main native fish in Brazilian aquaculture. A survey was conducted for 240 fish farms, and analyzed through Monte Carlo simulations. It was found that fluctuation in feed (US$0.49 ± 0.09 kg−1) and fish prices (US$1.77 ± 0.48 kg−1) exerts a great influence on the profitability of the projects. In general, the results indicate that it is difficult to make the farms profitable. The use of modern technologies, such as aerators, and monosex populations on fish farms may be some alternatives to overcome this situation and improve the productivity of the sector, consequently promoting its sustainability. [ABSTRACT FROM AUTHOR]

This study evaluated the use of the essential oils of Lippia sidoides (EOLS) and Mentha piperita (EOMP) as a stress reducer in the transport of Colossoma macropomum. The fish were transported for four hours in plastic bags, comprising the following treatments: a) non - stressed control (NS - not submitted to transport stress), b) stressed control (S - submitted to transport), c) EOLS 10 mg L−1, d) EOLS 20 mg L−1, e) EOMP 20 mg L−1 and f) EOMP 40 mg L−1; each treatment with three repetitions. After transportation, water quality, hormonal, biochemical and enzymatic parameters were analyzed. C. macropomum transported with EOLS 20 mg L−1 showed a significant reduction in cortisol levels compared to fish transported without essential oil. The glycolytic pathway was particularly stimulated in fish transported with EOMP 20 mg L−1, since the values of glycolytic enzymes hexokinase (HK), pyruvate kinase (PK) and lactate dehydrogenase (LDH) were elevated in muscle tissue. The essential oils did not affect the activity of acetylcholinesterase (AChE) in the brain of C. macropomum and, after transport, the fish from all treatments showed a significant reduction (28.2%) of muscular AChE. The concentrations of EOLS 20 mg L−1 and EOMP 20 mg L−1 promoted increased levels of the enzyme glutathione S-transferase (GST) in the brain. It is concluded that the essential oils in the assessed concentrations tend to improve water quality during transport, minimize physiological stress, help maintain energy demand through the breakdown of hepatic glycogen, glucose production and activation of the glycolytic pathway, however, without accumulating lactate. Furthermore, AChE trials demonstrate that EOs may not have neurotoxic effects. Therefore, the concentration of 20 mg L−1 EOLS is recommended for use in the transport of juvenile C. macropomum. • The levels of nitrite and ammonia in the water were reduced in the essential oils (EOs) groups. • Acetylcholinesterase trials demonstrate that EOs may not have neurotoxic effects. • Lippia sidoides EO increased protection against oxidative damage after transportation of C. macropomum. [ABSTRACT FROM AUTHOR]

The aim of this study was to evaluate the anesthetic potential of the essential oils of Aloysia triphylla (EOAT), Lippia sidoides (EOLS) and Mentha piperita (EOMP) in relation to juvenile tambaqui (Colossoma macropomum), based the swimming behavior of these fish and possible histopathological damage to the gills. To induce anesthesia, juvenile tambaqui (130.55 ± 22.4 g; 16.8 ± 0.95 cm) were individually exposed to different concentrations of the essential oils (EOAT: 5, 10, 20, 40, 60, 80 and 150 mg L−1; EOLS: 2, 5, 10, 20, 30, 40 and 50 mg L−1; EOMP: 5, 10, 20, 40, 60, 70 and 90 mg L−1), for exposure periods of between four minutes and six hours. The three essential oils evaluated presented anesthetic properties. The concentration intervals over which the fish reached all the stages of anesthesia (1, 2, 3a, 3b and 4) were between 40 and 150 mg L−1 for EOAT; 20 and 50 mg L−1 for EOLS; and 40 and 90 mg L−1 for EOMP. The times taken to reach the anesthesia stages were inversely proportional to the increases in the concentration of the essential oils. The histopathological damage to the gills of the tambaqui that resulted from using essential oil concentrations that were defined as anesthetic (150 mg L−1 EOAT, 30 mg L−1 EOLS and 90 mg L−1 EOMP) were also evaluated. The main damage recorded was hypertrophy and hyperplasia of the lamellar epithelium, lamellar fusion and proliferation of chloride cells. According to the histopathological alteration index (HAI), there were no irreversible damage (such as fibrosis and necrosis) to the gills of the tambaqui. However, while EOLS and EOMP caused mild damages in the gills, the EOAT generated more severe damages. Overall, for the tambaqui, the essential oils of A. triphylla, L. sidoides and M. piperita are efficient anesthetic in the doses of 150, 30 and 90 mg L−1, respectively. • This study reports the sedative and anesthetic effects of Aloysia triphylla , Lippia sidoides and Mentha piperita essential oils on Colossoma macropomum. • The essential oil of L. sidoides (30 mg L-1) induced faster anesthesia and recovery in C. macropomum. • Essential oils of A. triphylla , L. sidoides and M. piperita caused no irreversible damage to the gills of C. macropomum. [ABSTRACT FROM AUTHOR]