Features
Fish Have Distinct Personalities, New U of G Study Finds
Biologists find fish carry their active or passive feeding strategies from their natural world into the lab
BY ANDREW VOWLES
Fish have distinct personalities that explain differences in such behaviours as eating and swimming, a U of G study has found.
In a paper published in the journal Animal Behaviour, Prof. Rob McLaughlin, Integrative Biology, and researcher Alex Wilson learned that fish show distinct personality traits: staying put or exploring, risk-averse or risk-taking, sociable or aggressive.
“We've seen the kinds of phenomena we associate with personality in humans showing up in domesticated animals and now in wild animals,” says McLaughlin, who teaches, among other things, animal behaviour.
He and Wilson observed two kinds of feeding strategies among very young brook trout in the Credit River near Toronto. Active feeders swam near the surface, away from the bank. Sit-and-wait feeders remained near the stream bottom, feeding on what passed by.
“We wanted to test whether behavioural differences in the field were tied to underlying differences in personality,” says McLaughlin.
They caught the fish and tested them for six days in the Hagen Aqualab on campus. They found that fish that were more active in the field spent more time moving in the aquarium, spent less time near the bottom and took less time to emerge from a glass jar than their sedentary counterparts did.
Active fish stayed active and changed their activity less, on average, than fish that used a sit-and-wait-strategy in the field.
Subsequent work by current master's student Michelle Farwell has helped cancel out potential differences caused by such factors as variations in resting metabolic rates or swimming ability. She also showed that fish that are more risk-averse have higher levels of cortisol, a hormone whose concentration increases in animals under stress.
“What's cool,” says McLaughlin, “is the possibility for individual behaviour to influence food webs and interactions between prey and predators, and the evolution of fish populations with groups differing in behaviour and body form.”
Their work may help in managing fish stocks more precisely by accounting for personality differences between groups of fish. Setting catch regulations based on studies of fish taken only from the water column, for instance, may cause relatively more active individuals to be caught than sedentary ones, with unexpected consequences for the entire population and for biodi- versity.
McLaughlin also suggests that, over many generations, these personality differences along with environmental differences may play a role not only in the creation of subgroups of fish but also in the evolution of new species.
Switching to people, Farwell says personality might have helped early humans living a hunter-gatherer existence: “You could definitely see selection for more or less aggression.”
McLaughlin says his results may apply to other kinds of animals, although he's not sure how his ideas might explain differences between his teenage daughter and her younger brother.
“Do animals have personalities? We tend to think of pet owners as being clouded by their attachment to their animals. Maybe they're more correct than scientists give them credit for.”
McLaughlin is a Partnership for Ecosystem Research and Management scientist at Guelph who also studies sea lamprey control in the Great Lakes.