Welfare of farmed fish: moral considerations, science, and problems of implementation

The question whether fish are worthy of moral consideration, and thus, can be included in humanity’s expanding moral circle, was first raised in the 1990s. After the turn of the millennium, “fish welfare” was used by more and more scientists in the field of aquaculture, animal advocates, politicians, legislators, the fish farming industry, and consumers (Kristiansen and Bracke, 2020). For several years, the widespread view amongst the scientific community was that welfare was intimately connected with the absence of stress and disease. There is no doubt that, stress, health, and welfare are strongly interrelated, but not in a simplistic manner. Stress response is an essential, genetically embedded, adaptive mechanism designed to secure survival and other critical biological functions. Therefore, it is crucial to determine, in a species- and life-stage specific way, at what point do we cross the red line that stress does impair fish welfare. We should also characterise allostatic load and overload, as well as coping styles and behavioural traits, over time and across situations, leading to differential stress response among proactive and reactive individuals. This is important as due to different gene x environmental interactions a given individual may show a different response following exposure to a stressor of the same nature, duration, and intensity, based on its cognitive capacity, cognitive ability and appraisal of the controllability and predictability of the situation or challenge (Korte et al., 2007).