Contents lists available at ScienceDirect Aquaculture journal homepage: www.elsevier.com/locate/aquaculture Cytokines' gene expression, humoral immune and biochemical responses of common carp (Cyprinus carpio, Linnaeus, 1758) to transportation density and recovery in brackish water Seyyed Morteza Hoseini a , Morteza Yousefi b , Seyed Hossein Hoseinifar c , Hien Van Doan d, ⁎ a Inland Waters Aquatics Resources Research Center, Iranian Fisheries Sciences Research Institute, Agricultural Research, Education and Extension Organization, Gorgan, Iran b Department of Veterinary Medicine, Peoples' Friendship University of Russia (RUDN University), 6 Miklukho-Maklaya St, Moscow, 117198, Russian Federation c Department of Fisheries, Faculty of Fisheries and Environmental Sciences, Gorgan University of Agricultural Sciences and Natural Resources, Gorgan, Iran d Department of Animal and Aquatic Sciences, Faculty of Agriculture, Chiang Mai University, Chiang Mai 50200, Thailand ARTICLE INFO Keywords: Antioxidant Immune responses Stocking density Stress Transportation ABSTRACT The aim of the present study was to investigate the effects of stocking density during transportation and post- transportation salt treatment on stress, hydromineral, immunological and antioxidant responses in common carp (Cyprinus carpio). For this, the fish were transported in plastic bags for 4 h at two densities: 100 (LD) and 200 (HD) g/L and allowed to recover for 24 h in both freshwater (FW) and brackish water (3 g/L sodium chloride; BW). Water physicochemical parameters were determined after transportation. Blood stress, immunological and hydromineral responses, head kidney cytokine gene expression, and liver antioxidant responses were de- termined. The transportation led to significant decrease in water dissolved oxygen and pH, and increase in water total and unionized ammonia levels. Water dissolved oxygen was significantly lower, whereas, water total and unionized ammonia were significantly higher in the HD, compared to the LD group. Serum cortisol and glucose, and liver malondialdehyde levels, and expression of tumor necrosis factor-alpha, interleukin-1beta and inter- leukin-8 genes increased after transportation. Serum ion levels and liver superoxide dismutase and catalase decreased after transportation. All the above-mentioned changes, except for cortisol and catalase, were more severe in the HD compared to the LD group. There were no significant changes in serum total immunoglobulin and alternative complement after transportation, compared to before transportation values; but the LD group had significantly higher alternative complement than the HD group. Lysozyme and WBC significantly increase in the LD group; whereas, significantly decreased in the HD group, after transportation. Recovery in BW was useful to mitigate stress response, hydromineral imbalance, immunosuppression and oxidative stress caused by the transportation. Using sodium chloride is recommended during fish recovery from transportation, particularly when the fish are transported at high stocking density. The benefits of sodium chloride treatment seem to be mediated by restoration of hydromineral balance and oxidative status, which leads to healthier fish with higher immune responses. 1. Introduction Fish transportation is a common activity in aquaculture, causing mechanical stress and water quality deterioration (Harmon, 2009; Sampaio and Freire, 2016). Plastic bag filled with water and pure oxygen are used for short-term fish transportation (Becker et al., 2012; Mazandarani et al., 2017). Plastic bag transportation has negative ef- fects on water quality and fish health. Transportation results in elevated water ammonia, and decreased water pH and dissolved oxygen levels (Iversen et al., 2009; Azambuja et al., 2011; Parodi et al., 2014). Stress responses, characterized by blood cortisol and glucose elevation, are common during transportation (Iversen et al., 2009; Mazandarani et al., 2017). Oxidative stress commonly occurs during transportation, which might be due to either physiological stress (Birnie-Gauvin et al., 2017; Espinoza et al., 2017) or water quality deterioration, such as decreased dissolved oxygen and increased ammonia levels (Azambuja et al., 2011; Gressler et al., 2014; Li et al., 2016). Due to transportation stress, the fish respiration rate increases leading to hydromineral imbalance https://doi.org/10.1016/j.aquaculture.2019.01.049 Received 4 December 2018; Received in revised form 17 January 2019; Accepted 22 January 2019 ⁎ Corresponding author. E-mail address: hien.d@cmu.ac.th (H. Van Doan). Aquaculture 504 (2019) 13–21 Available online 23 January 2019 0044-8486/ © 2019 Elsevier B.V. All rights reserved. T