Aquaculture conditions promote exposure of farm fish to stressful factors and water quality is considered as one of the primary stressors in fish aquaculture. A common effect is a reduction in fish growth which can be interpreted as a trade-off between energy necessary for growth and energy requested for maintenance of homeostasis in fish exposed to daily challenging conditions. In that context, we developed studies in freshwater rainbow trout aiming to give a proper assessment of impact of environmental chronic stress on physiological parameters related to coping ability. In fish chronically exposed (or not) to low water quality (mostly hypoxia) we carried out a multivariate analysis of important functions related to health and welfare, i.e. stress responsiveness of the corticotropic axis (HPI) and acclimation (gill functions). Altogether, our data show that such assessment using HPI axis and gill functions is relevant to characterize chronic stress in fish. These results will be discussed in term of interrelated physiological functions leading to effective coping ability and compared to similar approach developed with other stressors