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Fish behavior study suggests that aquarium fish are more aggressive than wild ones

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… than what you might expect to find in nature.

From “Aquarium Fishes Are More Aggressive in Reduced Environments, New Study Finds” (
ScienceDaily (Sep. 22, 2011)”, we learn something that won’t surprise many:

Oldfield quantified aggressive behavior as a series of displays and attacks separated by at least a second. Displays are body signals such as flaring fins. An attack could be a nip, chase, or charge at another fish.

In aquariums, these behaviors can lead to injury and in extreme cases to death.

Aggressive behavior was not correlated with small-scale changes in either group size or habitat size alone. However, a significant difference was observed in environments sufficiently large and complex: fish spent less time exhibiting aggressive behavior.

The authors estimate that about 182.9 million aquarium fish live in the United States. While no one doubts that oceans are a fish-eat-fish world, if their thesis is right, hobbyists may be overestimating the amount of random violence in nature – fights animals don’t need to be in. That is, given a chance, most fish probably just swim away most of the time …

Where the researchers go overboard:

In the future, Oldfield said, “This study might help us to better understand how human behavior changes when people are placed in different social environments.” Violence in prisons might be linked in part to the smaller space and reduced stimuli.

Uh no. Anyone who has spent more time than they wish to recall on overcrowded, multicultural Toronto subway cars stuck in tunnels will know that most human beings respond to unavoidable crowding – that violates their social norms – by becoming very passive.

As for prisons, their inmates are prone to violent responses, and that’s commonly the reason they are imprisoned, so no special theory is needed.

Here’s an aquarium fish fight:


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