The scientific debate on fish pain has evolved significantly over recent decades, moving from scepticism toward acceptance that fish likely experience something analogous to pain.
The scientific evidence for fish pain has accumulated to the point where denying it requires rejecting multiple independent lines of evidence. Anatomical, pharmacological, and behavioural evidence all point toward fish experiencing something functionally equivalent to pain. The evolutionary argument that pain only evolved once in vertebrates is not parsimonious given the value of nociceptive learning. The welfare implications are enormous given the tens of billions of fish used in fisheries and aquaculture annually.