For Tank Fish Two Is Not Enough Company

July 16, 2009

Release from: Emily Sohn
Discovery News

Watching a fish or two swim around a tank can be relaxing for you -- but surprisingly stressful for the fish.

A new study found that common aquarium fish fight more and act less like themselves when they're lonely. Just as people choose to squeeze into a crowded nightclub rather than roam around an empty bar, it seems, certain fish prefer to have lots of companions.

It was the first study to look at the well-being of fish in home aquariums, and the results suggest that we may owe more to our fish than just keeping them from going belly-up.

"I think we need to make sure they are not only alive," said Katherine Sloman, a fish biologist at the University of Plymouth in the United Kingdom. "I think we need to get them to display behaviors they might show in the wild."

Advocates for the welfare of animals talk about five freedoms: freedom from hunger and thirst; freedom from discomfort; freedom from pain, injury and disease; freedom to express normal behaviors; and freedom from fear and distress.

How many of those things fish can actually experience is still up for debate. Some still controversial evidence suggests that fish might feel pain.

Other studies have quantified ideal stocking densities that produce the largest number of big, healthy animals in fish farms. Whether fish can be happy or not is something we may never know, but people who spend a lot of time with fish can tell normal behavior from the abnormal.