Fish are smart and feel pain: What about joy?

Sneddon et al. rightly point out that the evidence of fish pain is now so strong and comprehensive that arguments against it have become increasingly difficult to defend in balanced academic discourse. But sentience involves more than just pain. Recent research indicates that fish have an impressive range of cognitive capacities, including the capacity for pleasure, in the form of play and other behaviors likely to involve positively valenced experience. Having made the case for pain, research can now focus on other aspects of fish sentience. Doing so will not only provide a more complete picture of the mental lives and abilities of fish, but it will also promote their welfare and protection.