Pet owners love to talk about how their beloved animals have personalities. Cats are often “haughty” or “affectionate,” while dogs can so often be “calm” or “fun-loving.” These aren’t just variations in breeds, they also reflect difference in the personalities of individual species. Even the most avid fish lovers will have to admit that fish generally aren’t the brightest species on the planet, so many of us don’t expect our fish to have wildly varying personalities. [Editor's note: the following is a guest post by Dabney B. from Okeanos Group]
Well, surprisingly, that misconception is completely false. Fish have been scientifically proven to have very distinct personalities. Researchers led by Lynne Sheldon at the University of Liverpool have observed fish and discovered unique differences among individual fish behavior and preferences. The researchers took bold and shy fish and paired them together in fights. They would occasionally stack the fights in one combatant’s favor by pairing a particularly large fish with a much smaller fish. It may not have been the most humane experiment ever conducted, but it produced some fairly interesting results.
Fish that won their fights generally became bolder, while fish that lost fights typically became more cautious. One rather interesting result of the experiment is what Sheldon calls the “desperado effect.” Shy fish that lost fights were much bolder when investigating new sources of food, possibly because the fish knew that it would have to be more willing to try out alternative food sources, since it knew that it couldn’t compete with other fish in fights. Somewhat strangely, bold fish who observed a shy fish investigating a new food source were nervous about trying that food themselves.
Another study found that certain species experience a dramatic personality change whenever water temperature changes by as little as a few degrees. Dr. Peter Brio of the UNSW School of Biological, Earth and Environmental Sciences found that damselfish were noticeably more aggressive in warmer waters, lending evidence to the idea that fish can also take a cold shower to chill out. These findings aren’t just flukes. As it turns out, there are also fish that are just braver than other fish of the same species. These fish will fight with competitors, boldly confront predators, and aggressively pursue maters. Likewise, a shy fish will avoid fights, hide from predators, and submit to more dominant mating competitors.
This has some interesting implications for aquarium hobbyists. For one, we finally have scientific proof to show the naysayers whenever we try to explain the individual personalities of fish. Second, differences in personality might account for bad first impressions. An aquarist might get a new fish and find that he loves its bold and curious personality. Naturally, he purchases a few more fish of the species, thinking that they will all act the same. He might discover that the one bold fish was an anomaly, and not at all representative of a typically shy and reserved fish species. So, there you have it: you can’t judge a fish by its cover. Fish may not be as complex and varied as humans, but a lot of individual fish certainly have their own unique sparks that make them stand apart.