Safina, Carl (2016) Fish pain's burden of proof Animal Sentience 2016.081
Brian Key, Why fish do not feel pain
A hypothesis like Key’s, that fish cannot feel pain, should really be stated as a null hypothesis — an assumption that there is no difference in the things being compared. Then evidence — including anecdotal evidence — for and against rejecting the null hypothesis can be examined and weighed. Key (2016a) has proven only that fish lack mammalian brains.