Underwatertimes.com News Service - January 14, 2010 22:50 EST

Have you heard the one about gold fish having only a three second memory - by the time they swim around the bowl, they've forgotten where they are and swim around again?

"It's absolute rubbish," says Dr Kevin Warburton, an adjunct researcher with Charles Sturt University's Institute for Land, Water and Society who has been studying fish behavior for many years.

"There's been a lot of work done over the last 15 years on learning and memory in fish and it as 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; and carp that have been caught by fishers avoid hooks for at least a year. That fish have only a three second memory is just rubbish."

Dr Warburton, whose research has focused on Australia's freshwater fish, particularly local native fish in South East Queensland, has run experiments looking at how Silver Perch learn how to handle different types of prey.

"What came out, unexpectedly, was that while they were learning about their prey, their foraging efficiency went down," said Dr Warburton. "With one type of prey, the fish got more and more efficient at catching their food, but when we put two different types of prey in together, their overall efficiency dropped. We think it was because of they suffered from divided attention. It's a cost of learning."

Another example of fish memory was that fish can learn to avoid predators after being attacked once – this memory was retained for several months.

Dr Warburton said fish also exhibit behaviors that we tend to think as human.

"Some behavioral traits that we think are very human, such as deception, fish have as well," said Dr Warburton. "Fish can recognize other individuals and modify their own behavior after observing interactions between other individuals. For example Siamese fighting fish will attack other members of the same species more aggressively if they've seen them lose contests with other fighters."

Dr Warburton said fish inspect suspected predators to assess the level of threat.

"For added safety, they often do this as cooperating pairs, with the two fish taking the lead alternately," he said. "They will approach predators most closely when they have cooperated in previous inspections."

He said minnows recognize dangerous habitats by associating the smell of the water with 'alarm' chemicals that are released when fellow minnows are damaged by predators. This learned response to habitat water can be socially transmitted to naïve fish.

In reef environments, cleaner fish remove and eat parasites from larger 'client' fish.

"But what's fascinating is that they cooperate more with clients when they are being observed by other potential clients," said Dr Warburton. "This improves their 'image' and their chances of attracting clients. Some cleaners cooperate with small clients to raise their image so as to deceive larger clients, which they then cheat on by biting them rather than removing their parasites!"