Commentary Type

Invited Commentary


Brian Key, Why fish do not feel pain


Key (2016) affirms that we do not know how the fish brain processes pain but denies — because fish lack a human-like cortex — that fish can feel pain. He affirms that birds, like fish, have a singly-laminated cortex and that the structure of the bird brain is quite different from that of the human brain, yet he does not deny that birds can feel pain. In this commentary we describe how Key cites studies that substantiate mammalian pain but discounts the same kind of data as evidence of fish pain. We suggest that Key's interpretations are illogical, do not reflect the published empirical evidence for pain in fish, and are out of touch with current thinking on brain evolution. We agree that more scientific data are needed to understand how the brains of fish — and other organisms — function. But the incompleteness of current knowledge certainly does not constitute evidence for inferring that fish in particular do not feel pain.

Author Biography

Lynne U. Sneddon lsneddon@liverpool.ac.uk is Director of Bioveterinary Science at the University of Liverpool. She was one of the first scientists to discover nociceptors that detect painful stimuli in fish. Sneddon has since published empirical studies that drive the fish welfare agenda in many contexts.


Matthew Leach matthew.leach@ncl.ac.uk is a member of the Pain & Animal Welfare Science Group at Newcastle University, which is internationally recognised for work on assessing and alleviating mammalian pain. Leach's current work aims to gauge pain noninvasively through the use of grimace scales.