Repeated hypoxic episodes allow hematological and physiological habituation in rainbow trout

Abstract

Introduction: Under climate change, the increase in temperature in aquaticenvironments may induce oxygen depletion. In extreme cases, low oxygenmay become a limiting factor for fish, thus generating stress. In addition,consecutive hypoxic episodes may complicate the recovery of individualsand hinder their ability to modulate physiological and biochemical responsesto maintain homeostasis. Thus, the aim of this study was to determine thehematological and physiological responses of rainbow trout under a conditionof repeated hypoxic and manipulation stresses at three different time points.Methods: Every hypoxic episode consisted of exposing the fish to low dissolvedoxygen concentrations (2 mgO2/L for 1 h). Following the exposure, the fishwere allowed to recover for 1 h, after which they were sampled to investigatehematological and physiological parameters.Results and discussion: The results showed a pattern of habituation reflectedby values of hematocrit, hemoglobin, and mean corpuscular volume, indicatinga certain ability of rainbow trout to resist this type of repeated hypoxic events,provided that the fish can have some recovery time between the exposures.