Fish personalities: Some are bolder than others

Written by Thomas Hesselberg

Tuesday, 20 November 2007

Fish have different personalities. Some are shy and some are bold. Photo courtesy of photocase.com.

Pet owners have known all along that animals are not alike, but have distinct personalities in a way similar to what we see in humans. However, it is first recently that researchers have become interested in the topic. In the past decade, biologists have found personality traits in more and more different animal species. One of the most tested personality traits is the shyness-boldness continuum, where bold individuals take risks and quickly explore new conditions, whereas shy individuals are risk averse. Scientists from the University of Edinburgh in Scotland have investigated the shyness-boldness continuum in fish in order to learn more about how personality is affected by experiences, physiological condition and heredity.

The scientists caught individuals of the Panamanian Bishop (Brachyraphis episcope), a small tropical poeciliid, and allowed to breed in the laboratory. Fish from two areas were caught, one from an area with a high risk of predation and one from an area with a low risk. Fish from the high-predation area are known to be bolder than fish from the low-predation area. Female offspring from the caught fish were then exposed to two experimental conditions, one where they were left undisturbed in the tank and one where predation was simulated by chasing the fish with a net. They then placed a box containing the fish in a novel arena and measured how quickly the fish emerged from the box.

The biologists found that the offspring show behaviour consistent with that of their parents, thereby emphasising the strong genetic determination of the personality. However, they did also find that offspring from both high- and low-predation areas, placed in the simulated predation tanks, showed an increase in boldness, thereby indicating that personality is also influenced by life experience.

Findings such as these, which show that each individual seem to have a genetically determined personality, which, however, can be changed according to life experiences, are useful in the understanding of how personality traits develop in humans.

Source: Brown, C.; Burgess, F. and Braithwaite, V. A. (2007) Heritable and experiential effects on boldness in a tropical poeciliid. Behavioural Ecology and Sociobiology 62: 237-243.

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