Discussions on fish sentience were first sparked by Verheijen’s seminal work on post hooking behaviour in carp in 1983. With the work by Lynne Sneddon and those who followed suite, on nociceptors and on post-nociceptive behaviour in a range of teleosts, there is increasingly robust evidence base supporting the concept of a state akin to what we might regard as pain and fear in fish.
EU and UK statutory controls of animals used in scientific procedures have endorsed this evidence. At the same time, a number of researchers across the globe have challenged the findings, proposing that the concept of a higher conscience in fish is rooted in the anthropomorphic extension of the human understanding of pain and fear. At least in the UK, this debate has stalled the progression of welfare improvements for fish in research facilities. Fear of compromising research results and the absence of published practical analgesic protocols suitable for small fish, for example by immersion, can push the researchers into the embracing entrenched view that fish do not have the anatomical prerequisite to experience pain and that all attempts at giving fish analgesia are a waste of time.