Dean Pomerleau's pet goldfish, Albert Einstein, knows how to play fetch, a feat the Pittsburgh-area engineer hopes will earn his calico fantail a listing in Guinness World Records as the world's smartest fish. Albert the goldfish has also learned to nudge a soccer ball into a goal and to do the limbo.
"I spend half my life telling people fish aren't stupid," says Culum Brown, a zoologist at the University of Canterbury in New Zealand who puts fish through mazes to study cognition. Brown says salmon can learn to feed themselves by pushing a lever, and some carp are trained to come when called so that workers using them to clean up algae can transport the fish from one lake to another. He has also observed that rainbow fish recall the location of an escape hole in a fishing net a year later.
Fish brains have a structure very different from those of other vertebrates: They develop inside out. Although these brains don't have the same parts, they seem to do the same things. "Unfortunately, there are only about three labs in the world that work on fish brains, so it's taking a long time to catch up," Brown says.
In nature, memory equals survival. Fish learn from one another which to mate with and which not to fight with, where to eat and how not to get eaten. Brown enjoys picking up a fishing rod and engaging in a battle of wits: "There's something to be said for outsmarting them!"