They may not show it, but fish have complex personalities, research suggests.

The discovery was made by scientists studying individual traits in tiny fish called Trinidadian guppies.

When they looked how the fish behaved in different situations, they found complex variations and modes of behaviour that could not simply be explained as risk-taking or risk-averse.

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Researchers found complex variations and modes of behaviour that could not simply be explained as risk-taking or risk-averse. Pictured is a mock-up image showing a Trinidadian guppy (the small fish), a blue acara cichlid and a model of a heron

WHAT DID THEY FIND? The discovery was made by scientists studying individual traits in tiny fish called Trinidadian guppies. When they looked how the fish behaved in different situations, they found complex variations and modes of behaviour that could not simply be explained as risk-taking or risk-averse. Mild stress was caused by transferring fish individually to an unfamiliar tank, and higher levels of stress by showing them models of predatory birds or fish. They behaved differently - with some attempting to hides, others trying to escape and some trying to explore cautiously. Advertisement

It had been thought fish such as guppies had a ‘simple spectrum’ of responses - but this study shows otherwise.

'The idea of a simple spectrum is often put forward to explain the behaviour of individuals in species such as the Trinidadian guppy', said lead researcher Dr Tom Houslay from the University of Exeter.

'But our research shows that the reality is much more complex.

'For example, when placed into an unfamiliar environment, we found guppies have various strategies for coping with this stressful situation', he said.

The study, published in the journal Functional Ecology, looked at the behaviour of guppies in conditions designed to cause varying levels of stress.

Mild stress was caused by transferring fish individually to an unfamiliar tank, and higher levels of stress by showing them models of predatory birds or fish.

'Many attempt to hide, others try to escape, some explore cautiously, and so on', said Dr Houslay.

'The differences between them were consistent over time and in different situations.

'So, while the behaviour of all the guppies changed depending on the situation - for example, all becoming more cautious in more stressful situations - the relative differences between individuals remained intact.'

When they looked how guppies (pictured, stock image) behaved in different situations, they found complex modes of behaviour that could not be explained as risk-taking or risk-averse

The presence of predators had an effect on 'average' behaviour, making all the guppies more cautious.

But individuals still retained their distinct personalities.

Professor Alastair Wilson, another member of the CEC team, said: 'We are interested in why these various personalities exist, and the next phase of our research will look at the genetics underlying personality and associated traits.

'We want to know how personality relates to other facets of life, and to what extent this is driven by genetic, rather than environmental, influences.

'The goal is really gaining insight into evolutionary processes, how different behavioural strategies might persist as species evolve.'