Contents lists available at ScienceDirect Aquaculture journal homepage: www.elsevier.com/locate/aquaculture Short communication Anaesthesia with eugenol in hybrid Amazon catfish (Pseudoplatystoma reticulatum × Leiarius marmoratus) handling: Biochemical and haematological responses Crislaine Palmeira Barbosa de Oliveira a , Carlos Henrique da Paixão Lemos a , Luiz Vitor Oliveira Vidal a , Ricardo David Couto b , Denise Soledade Peixoto Pereira c , Carlos Eduardo Copatti a, ⁎ a Programa de Pós-Graduação em Zootecnia, Universidade Federal da Bahia, Av. Adhemar de Barros, 500, Salvador, BA 40170-110, Brazil b Departamento de Análises Clínicas e Toxicológicas, Faculdade de Farmácia, Universidade Federal da Bahia, Brazil c Programa de Pós-Graduação em Ciência Animal, Universidade Federal do Recôncavo da Bahia, Brazil ARTICLE INFO Keywords: Anaesthetic recovery Cortisol Haematological variables Sedation Stress ABSTRACT This study aimed to evaluate the effectiveness of eugenol for induction and anaesthesia recovery in hybrid Amazon catfish juveniles and to verify its effects after handling stress. Juveniles were exposed to different concentrations of eugenol: 0 (control), 10, 20, 30, 40, 50 and 60 μLL -1 (equivalent to 10.6, 21.2, 31.8, 42.4, 53.0 or 63.6 mg L -1 ). The fish were divided into two groups: anaesthetised with 53.0 mg L -1 eugenol and non- anaesthetised. Biochemical and haematological variables showed different responses for eugenol in handling (0, 1 and 5 h). Eugenol was recommended for sedation and anaesthesia with 21.2 and 53.0 mg L -1 , respectively. In control fish, 25 and 50% mortality occurred at zero and one hour after handling stress. Plasma cortisol levels were higher in control fish than anaesthetised fish (0 h). Plasma AST and albumin levels were higher in control fish when compared to anaesthetised fish (0 and 1 h, respectively). In control fish, plasma cortisol, glucose, total protein and albumin levels were significantly lower at five hours after handling stress. Thrombocyte and neu- trophil values were lower in control fish when compared to anaesthetised fish (1 and 5 h, respectively). The use of 53.0 mg L -1 eugenol is indicated as an anaesthetic for Amazon catfish and reduces post-handling stress by reducing mortality, improving biochemical responses and promoting increased immune system. 1. Introduction The use of anaesthetics in fish farm is a strategy to minimise stress- inducing factors, such as hypermobility and perception of adverse sti- muli, mainly in handling and transport procedures. Thus, the use of anaesthetics can avoid losses due to loss of appetite, reduced growth, impaired immune system and, consequently, infectious diseases and death of organisms, because stressful situations trigger changes in be- havioural, haematological and biochemical responses (Barcellos et al., 2003; Teixeira et al., 2017; Bahi et al., 2018). In this sense, eugenol is one of the most-used natural anaesthetics in fish, being the main che- mical compound derived from the essential oil of clove (Syzygium ar- omaticum)(Vidal et al., 2008). The Amazon catfish is a hybrid with zootechnical superiority in relation to the parental species (female cachara Pseudoplatystoma re- ticulatum x male Amazonian silver catfish Leiarius marmoratus), that occur in the main hydrographic basins of South America. Despite its commercial importance, there have been no studies related to handling anaesthesia in Amazon catfish. This study aimed to evaluate the in- duction and anaesthetic recovery in Amazon catfish juveniles exposed to different concentrations of eugenol and to verify its effectiveness in reducing handling stress through biochemical and haematological variables. 2. Materials and methods 2.1. Animals and experimental conditions The experimental procedures were developed in the Fish Feeding Behaviour and Nutrition Laboratory of the Universidade Federal do Recôncavo da Bahia, Cruz das Almas, BA, Brazil. The experiments were approved by the Ethical Committee of the Biology Institute of the https://doi.org/10.1016/j.aquaculture.2018.11.046 Received 21 April 2018; Received in revised form 19 November 2018; Accepted 19 November 2018 ⁎ Corresponding author. E-mail address: carloseduardocopatti@yahoo.com.br (C.E. Copatti). Aquaculture 501 (2019) 255–259 Available online 20 November 2018 0044-8486/ © 2018 Elsevier B.V. All rights reserved. T