Fish have different characters which change as they experience life's highs and lows, according to British biologists.(File Photo)

LONDON, Nov. 22 (Xinhua) -- Fish have different characters which change as they experience life's highs and lows, according to British biologists.

Researchers of the University of Liverpool identified different "personalities" in their fish by observing the boldness or shyness of individuals, according to The Nature on its website on Wednesday.

Like people, some fish are very confident in the face of novelty or confrontation, whereas others are reticent and fearful, the researchers said.

The scientists selected particularly bold and shy rainbow trout,and tested whether they changed their outlook depending on what life threw at them by arranging fish fights and watching to see how both the participants and observers responded to victories and defeats.

Winning or losing a fight, or even watching fellow fish negotiate the perils and pitfalls of encountering strange new objects, influenced the future behavior of the creatures studied in the lab, the researchers said.

The researchers led by Lynne Sneddon deliberately pitted fish against much larger or smaller opponents, to ensure that they would win or lose the ensuing fight. These bold fish that won their fights tended to be even bolder when later presented with a novel food item; losing their fight caused them to be much more cautious.

The researchers suspect that shyness and boldness are linked to physiological factors such as levels of stress hormones. Losing a fight might boost levels of stress-related chemicals such as cortisol, which might make a fish much more wary in future.

Fish also learn by watching others, the researchers found. Bold fish watching a shy fish investigating a mystery object were much more nervous when later given a novelty item for themselves.

Predictably, shy fish that won a fight also gained more confidence, but surprisingly, shy fish that lost their bout also grew bolder when investigating strange new food, Sneddon said, adding that this could be due to what she calls a "desperado effect".

Shy fish that know they are pathetic in a fight must race for food if they want to get any, Sneddon suggested. She added this is"totally presuming" that fish think about winning or losing.

The new research suggests that these traits are not set in stone and that animals can gradually adapt their personalities. The results echo the effects that life experience can have on humans.

The idea of animal personalities - known to researchers as "behavioral syndromes" - aims to explain why some animals' behavior is not always ideally suited to their circumstances, as a male with a naturally aggressive temperament, for example, might be great at fighting off rivals, but might never get to mate because his heavy-handed seduction tactics scare off the females.