The term, “Goldfish Mentality” may need to be redefined after a man from California taught his goldfish how to play football.
His pet fish, named Comet, can also play basketball and even limbo dance under a bar.
Other tricks he’s learnt are to play fetch with a hoop, slalom around a series of poles and push a rugby ball over a set of posts.
Dr Dean Pomerleau, 41, from Los Angeles, used a training technique called positive reinforcement to train his two-year-old common goldfish to carry out the tricks.
Positive reinforcement is a training technique where the fish is rewarded with food when he successfully completes a task.
Dr Pomerleau said: "There is mounting evidence that fish are more intelligent than people give them credit for.
"With the correct tools and the basic promise of a food reward, fish can very quickly learn complex tricks - like the limbo, slalom or playing fetch.
"Now people in the market for a dog might want to consider a fish instead."
He added: "We've used techniques that we've customised for pet fish, but are based on those used to train dolphins and other marine mammals."
He has teamed up with pet product firm R2 Solutions to design a special kit to help people train their fish. It features goal posts, slalom poles and tunnels, as well as an instructional DVD.