Short-term handling stress affects the humoral immune responses of juvenile Atlantic cod, Gadus morhua Christopher Marlowe A. Caipang • Effrosyni Fatira • Carlo C. Lazado • Michail Pavlidis Received: 7 September 2013 / Accepted: 22 December 2013 Ó Springer Science+Business Media Dordrecht 2013 Abstract Juveniles of Atlantic cod, Gadus morhua L., weighing 30–50 g were subjected to short-term handling stress by exposing them to air for 3 min and immediately placing in the rearing tank for recovery. Indices for the primary stress response as well as selected immune- and metabolism-related parameters were measured in the plasma before the application of the stressor and at 1-h, 24-h and 7-day post-stress. Plasma cortisol signifi- cantly increased at 1-h post-stress then returned to the prestress levels at 24-h post- exposure. Plasma glucose and total antioxidant capacity had two peaks at 1 h and 7 days after handling stress. Alkaline phosphatase significantly increased at 24-h post-exposure, while no significant changes in myeloperoxidase activity was observed. Lysozyme and antiprotease activities were significantly downregulated at 1- and 24-h post-exposure, respectively. These findings showed that short-term handling stress in Atlantic cod juve- niles resulted in temporal elevation of the primary stress response and metabolism with a corresponding decrease in its defense against bacterial pathogens. Keywords Atlantic cod  Cortisol  Handling stress  Innate immunity  Air exposure Introduction Cultured fish species are almost exposed to husbandry-related stressors. These stressors can either be acute or chronic, and they induce physiological changes in the fish as responses C. M. A. Caipang (&) Disease and Pathogen Transmission Research Group, Institute of Marine Research, P.O. Box 1870, 5817 Nordnes, Bergen, Norway e-mail: cmacaipang@yahoo.com E. Fatira  M. Pavlidis Department of Biology, University of Crete, 71409 Heraklion, Crete, Greece C. C. Lazado Aquaculture Genomics Research Unit, Faculty of Biosciences and Aquaculture, University of Nordland, 8049 Bodø, Norway 123 Aquacult Int DOI 10.1007/s10499-013-9746-2