SACKVILLE, New Brunswick (AP) – Researchers at a Canadian university are attracting international attention after finding that a common chemical could jeopardize the health of fish populations.

The researchers at Mount Allison University in New Brunswick exposed fish to a compound widely used in industrial detergents, sewage treatment, the pulp and paper industry and in agricultural pesticides. They found that, even at low levels, the chemical caused them to avoid each other rather than grouping together in schools or shoals.

It’s troubling because schooling is a survival technique for fish, and the chemical – 4-nonylphenol – can be found just about everywhere, said biology professor Suzie Currie, whose lab hosted the research.

“It’s a ubiquitous breakdown product of detergent and often more toxic than the parent compound,” said Currie. She completed the study with recent graduate Jennifer Horsfall and former postdoctoral fellow Ashley Ward, who is now at the University of Sydney in Australia.

Their basic finding was that 4-nonylphenol (4-NP) seemed to disrupt the fish’s ability to smell each other, but in a roundabout way.

One experiment on single fish exposed to the chemical found that there was no actual effect on the sense of smell. But when a new, clean fish was introduced to a group that had been exposed, it tended to avoid the group.

“The single fish was really repelled by that smell, and would actively move away from that shoal. Effectively what that’s saying is, when fish swim through and are affected by 4-nonylphenol, they start to smell bad and the school breaks up and is not as cohesive,” said Currie.

Fish tend to be attracted to other fish that smell like them, but 4-NP actually changes a fish’s natural chemical signature so significantly that others are repelled and tend to keep their distance.

“It makes fish smell funny to other fish so they no longer want to associate with them,” she said. “You could liken it to when you eat garlic, you can smell it from someone else.”

The study was recently published in the journal Proceedings of the Royal Society of London B from Britain’s Royal Society.

Although they tested only tiny killifish, their findings could represent an “alarming” trend across other species, said Currie.

“These effects could be extrapolated to other fish species. It’s affecting chemical signatures (in a way that is) not specific to the species we looked at,” she said.

“This is what animals rely on to protect themselves from predators, seek food and get information about their habitats,” Currie added. “These low levels are affecting a fundamental aspect of a fish’s behavior that is going to have downstream consequences for survival. They’ll be more susceptible to predators, won’t be able to find food (as effectively), they’ll got lost from the rest of the school and won’t be able to find mates (as easily).”

The research represents a new way of looking at how chemicals can affect animals. Typically, most research has focused on direct toxicity, basically determining levels at which chemicals actually cause animals to die.

In this case, they’ve studied an effect on behavior, which could indirectly harm the animal’s chances of survival.

“There’s a growing field looking at effects on behavior. We just used to look at: does it kill fish? Does it kill cells? That’s still very important, but this adds another layer,” Currie said.

For example, the level of 4-NP they used to test the killifish, one microgram per liter, is deemed a permissible level by Environment Canada.

“We were using one microgram and lower and finding effects,” she said. “These behaviors are very important in survival and I think what it’s telling us is, we really need to rethink appropriate or permissible levels of 4-nonylphenol and other contaminants that exist in the environment.”

AP-ES-11-20-07 1244EST

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