Short-term handling stress affects the humoral immune responses of juvenile Atlantic cod, Gadus morhua

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 significantly 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 juveniles resulted in temporal elevation of the primary stress response and metabolism with a corresponding decrease in its defense against bacterial pathogens.