Fish have distinct, complex personalities and react differently to stress

It’s not always ea-sea being a small fish in a big tank.

New research has found that when faced with danger, some fish completely freak out while others seem calm under pressure suggesting they have their own distinct personalities.

Researchers from the University of Exeter studied groups of Trinidadian guppies and found complex differences between the fish that they were unable to place on a simple ‘spectrum’.

“The idea of a simple spectrum is often put forward to explain the behaviour of individuals in such species,” said Dr. Tom Houslay from Exeter’s Centre for Ecology and Conservation (CEC) in Cornwall. “But our research shows that the reality is much more complex.”

To study the fish’s response to stress, the researchers transferred them to new tanks before adding models of predators. Everything was going swimmingly until the models of, for example, birds of prey were shown to the tank. Some fish were more cautious than others.

“The differences between them were consistent over time and in different situations,” said Dr Houslay. “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.”

Now the authors want to learn more about why fish have developed these distinct personalities.

“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,” said Professor Alastair Wilson, also from the CEC. “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.”