Are fish smart? Yes, according to a new paper published this week in the journal Animal Cognition.
They also have more complex social lives than you might realize, too. For instance, some fish even give backrubs.
There's a kind of fish -- the cleaner wrasse -- that eats parasites and other nasty things off other fishes' mouths, gills and bodies; it's a well-documented symbiotic relationship that is pretty magical to witness.
And sometimes, the cleaner wrasse needs to calm these other fishes down. Just like you get a massage when you're tense, a 2011 study found that surgeonfish -- whose stress levels were intentionally raised by the researchers -- became more relaxed after their pelvic and pectoral fins were given a rub, as the cleaner fish will do.
So some fish like massages. Most probably feel pain. Many have good eyesight, a great sense of smell, well-developed hearing abilities, and the ability to both create and detect electric currents in the water.
Fish can also learn where to get food, and who belongs to their social group. Fish who learn to escape from a net can hold onto that knowledge for almost a year. But that's not all!
The paper's author, Culum Brown, an associate professor of biology at Macquarie University in Australia, writes that some fish are able to figure out who in their social circle is untrustworthy:
If a pair of fish inspects a predator, they glide back and forth as they advance towards the predator each taking it in turn to lead. If a partner should defect or cheat in any way, perhaps by hanging back, the other fish will refuse to cooperate with that individual on future encounters. This shows that the fish not only recall the identity of the defector but they also assign a social tag to them and punish them on future encounters.
The paper -- it's called "Fish intelligence, sentience and ethics," and surveys existing studies on fish cognition -- goes on to argue that fish share enough characteristics with other vertebrates, such as using tools and having good sensory perception, that our swimming friends should be afforded more legal protections.
"Although scientists cannot provide a definitive answer on the level of consciousness for any non-human vertebrate, the extensive evidence of fish behavioral and cognitive sophistication and pain perception suggests that best practice would be to lend fish the same level of protection as any other vertebrate," writes Brown, who acknowledges that such a move has implications for the fishing industry, among others. "We should therefore include fish in our 'moral circle' and afford them the protection they deserve."
Brown's paper was funded by the U.S.-based non-profit Farm Sanctuary, whose “Someone, Not Something” project is aimed at bringing the science of farm animal cognition to the general public.
Indeed, Brown told HuffPost he hopes his paper will contribute to "a sort of sea change, a revolution if you like, similar to the one we have seen in response to industrialization of terrestrial farming."
At a minimum this would mean giving fish similar protections to farm animals.
"The main thing is to consider fish in the same way you would any other animal," he said. "If you like to go out shooting stuff, well that is no different from fishing. The main thing is that you kill the animal as swiftly as possible and inflict the minimal amount of stress and pain. There is no doubt in my mind that we should eat fish in the same way as we should eat any other meat. But i think the manner in which we catch them really needs to be looked at from a welfare perspective."
Could an understanding of how fish experience the world lead to that sort of change? Maybe -- except fish are very different from humans in ways that might not be meaningful in terms of how we ought to think about their rights, but is very meaningful in terms of how we instinctively respond to them.
"We cannot hear them vocalise, and they lack recognisable facial expressions," Brown writes in the paper, "both of which are primary cues for human empathy."
And, unfortunately, there might be the rub -- not the in that nice massage kind of way, either.