The fish, a Midas Cichlid, appears to approach the person's hands looking for a scratch -- something like a puppy would -- and even returns for more. But what's really going on here? The Dodo spoke to author and animal ethologist Jonathan Balcombe, Department Chair for Animal Studies with Humane Society University, to get to the bottom of this.
According to Balcombe, some fish (though certainly not all) do actually enjoy being touched by humans. "It is a basic characteristic of animal behavior that animals will approach desirable things and retreat from undesirable ones," he said, adding that the fish "appears to like the touch because s/he swims back to the hand repeatedly."
Balcombe notes that touch is a powerful de-stressor for animals -- and fishes are no exception to this phenomenon. Other examples include groupers, who are well-known for approaching a trusted human to be stroked and cleaner-fish, who gently stroke their client fish with their fins. One study involving surgeonfish found that fish who had been subjected to stress spent more time in contact with a mechanized wand that stroked their bodies than unstressed fish did.