Decades of research have revealed a richness of fish cognition and social behaviour that fundamentally challenges the dismissive view of fish as simple reflex machines without morally relevant experiences.
The transformation in our understanding of fish cognition over the past two decades has profound welfare implications. The old assumption that fish are simple sensory machines incapable of significant experience is scientifically obsolete. Fish live complex social lives, form preferences, experience aversion, and show evidence of subjective states that respond to the same analgesic and anxiolytic medications that reduce suffering in mammals. This does not mean fish experience the world identically to mammals, but it means they almost certainly experience it in morally significant ways. Welfare standards in fisheries and aquaculture have not yet caught up with this scientific reality, and advocacy for evidence-based fish welfare standards is urgently needed.