Animal welfare aspects of husbandry systems for farmed Atlantic salmon

Fish are very diverse in their body form and have a wide range of sensory systems, some of which, such as electroreceptors and the lateral line system, are not shared by birds and mammals. As vertebrates, fish, birds and mammals share a similar general brain structure. Over and above this, however, comparative neuroanatomy highlights many differences among vertebrate groups; it also highlights differences in brain structure among species of fish. On the other hand, studies of brain function suggest a number of parallels between fish and other groups. Fish have nociceptors and these look like and have a similar response profile to those of birds and mammals. The question of whether fish experience the input of these receptors as pain remains controversial but experiments have shown the brain is active during such stimulation and that painkillers reduce prolonged behavioural and physiological responses. It is clear that the responses given by fish to nociceptive stimulation are more complex than simple reflexes, including significant shifts in behavioural priorities and the perfor f anomalous behaviour. In this context, our working position is that juvenile and adult fie capacity to perceive painful stimuli and experience at least some of the adverse affees y tes that we associate with pain in mammals. Data suggest that the affective tate of ear sometimes motivates behaviour in fish. The systems in mammals and birds t in the production of adrenaline and cortisol have close anatomical and functional o a e n fish. Fish show physiologically and behaviourally similar freeze and flight respons nd prolonged cortisol production is associated with immunosuppression.