Personality influences rainbow trout's memory, Concordia study shows
Montreal, October 23, 2012 – With their glassy stares and slimy skin, fish have never been known for their winning personalities. When it comes to rainbow trout, however, a fishy temperament can mean the difference between avoiding a predator and coming face-to-face with the bigger, nastier fish in the pond.
Grant Brown is a professor of biology at Concordia University
According to Grant Brown, a professor of biology
at Concordia University, a fish's personality can influence how it responds to and learns from threats. In a new study published online in Behavioral Ecology & Sociobiology
, Brown shows that bolder trout forget predator odour, and hence potentially predation threats, quicker than their shyer counterparts.
“If they’re going to balance the conflicting demands of avoiding predators and foraging, organisms need to have the ability to recognize and assess risks. Learning to identify what is and what is not a predation threat allows them to avoid wasting time and energy responding to things that are not dangerous,” explains Brown, who undertook this research with the help of his students and colleagues from the University of Saskatchewan.
Because predators can be present anywhere at any time, learning and retaining information about a predator threat, and being able to recall it at a later stage, is key to better assess relevant threats in the future – a fact not limited to fish.
Brown and his team studied how long young rainbow trout retained information they had previously learned about a predator. They also investigated whether the duration of that retention was influenced by the fish's personality, i.e. whether they were shy or bold.
Because no personality test has yet been developed for fish, Brown and his colleagues determined whether these trout were shy or bold by timing how quickly the fish escaped from test tanks once a movable Plexiglas barrier was removed. Those who moved quickly displayed risk-taking behaviour – the bold fish. Those who moved more cautiously were avoiding risk – the shy fish.
The researchers conditioned the individual trout to recognize the odour of one of their potential predators, the pumpkinseed sunfish. They then tested whether the conditioned trout still recognized the odour, both 24 hours and eight days later.
Brown found that the fish's personality shaped how long the information was retained. Although there was no difference in the fish's predator recognition during the conditioning phase or after 24 hours, shy trout continued to demonstrate a learned response to pumpkinseed odour eight days later, while bold trout did not. These results suggest that, for rainbow trout at least, an individual’s willingness to take risks shapes the retention of learned information but not learning itself.
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