Their brain power is at best shallow. Or so we thought. But scientists believe fish may have hidden depths.  The creatures said to have a mere three-second memory span can actually recall information for up to three months.

Scientists found that fish trained to respond to certain sounds in captivity still reacted months later when they heard them in the wild.

The finding challenges the stereotype of fish being forgetful sorts, an idea reinforced by films such as Finding Nemo, whose characters include an absent-minded fish called Dory.

According to research at Plymouth University, goldfish have a memory span of up to three months – and can even tell the time.

The fish were trained to nudge a lever to get food.  When the lever was adjusted so it would only work during one hour each day, the goldfish adapted, learning only to press the lever around the right time.

They even clustered around the lever as feeding hour approached, apparently remembering it was nearly lunchtime – or was it just because they were hungry???