News in Science

Three-second fish memory 'rubbish'

Forget what you know: Fish have a memory that lasts much more than three seconds and are capable of deception and learning, say Australian researchers.

Dr Kevin Warbuton, an adjunct researcher at the Institute for Land, Water and Society at Charles Sturt University in Albury, New South Wales has been studying fish for more than three decades and says they're much better at memory than we give them credit for.

Warbuton's research has been focused on Australian freshwater fish, particularly in southeast Queensland.

He says the idea that fish have a short memory is wrong.

"It's absolute rubbish," says Warbuton. "There's been a lot of work done over the last 15 years on learning and memory in fish and it has been found that fish are quite sophisticated.

"Fish can remember prey types for months; they can learn to avoid predators after being attacked once and they retain this memory for several months."

Warbuton believes fish are capable of learning, albeit at a cost. For example, his research on the silver perch revealed something unexpected.

"With one type of prey, the fish got more and more efficient at catching their food," he says. "But when we put two different types of prey in together, their overall efficiency dropped. We think it was because they suffered from divided attention. It's a cost of learning."

Art of deception

According to Warbuton, fish are also capable of exhibiting human-like behaviours, such as deception.

"Fish can recognise other individuals and modify their own behaviour after observing interactions between other individuals.

"Siamese fighting fish will attack other members of the same species more aggressively if they've seen them lose contests with other fighters."

Warbuton says cleaner fish - reef fish that eat parasites off other larger fish - will also be on the lookout to assess the situation and work out how best to take advantage.

"What's fascinating is that they cooperate more with clients when they are being observed by other potential clients," says Warburton. "This improves their image and their chances of attracting clients."

Misguided belief

Dr Ashley Ward, a fish biologist at the University of Sydney says where the three-second memory urban myth came from is hard to find.

"It seems to come from an advert many years ago, but nobody is sure what it was for," he says.

Ward believes the misconceptions surrounding the intelligence of fish may stem from the early days of zoology.

"Back then [zoologists] tested their abilities based on what a human could do … so obviously the fish would fail."

Ward says we now know of numerous of examples of fish displaying amazing memory skills.

He refers to one anecdote from the United States, where a Professor Charles Eriksen spent several months feeding a pond of fish while calling out "fish-fish".

After a break of five years, Eriksen returned to the pond and called out "fish-fish". Immediately a number of the surviving fish swam to the surface waiting to be fed.

According to Ward, the frillfin gobbie, which during low tide lives in rock pools that are spaced apart, has an amazing memory.

"If it gets frightened by a bird it jumps from one rock pool to another. To do this, it has to remember the topographic layout of the pools without being able to see them," says Ward.

"Another example is the trigger fish, which is found around northern Australia," he says. "They have been shown to use tools and other smart tricks to outwit their prey."