Perch exposed to human anti-anxiety drugs become isolated, aggressive - study

BOSTON (Reuters) - Wild perch living in water tainted with a commonly prescribed human anti-anxiety drug aggressively feed, shun other fish and become careless, according to the results of a study presented at a meeting of scientists on Thursday.

'We knew there was a pharmaceutical that was present in the environment that had behavioral-changing capabilities in humans, but what could this do to fish?' said chemist Jerker Fick of Umea University in Sweden.

The findings highlighted the potential ecological implications of even trace amounts of psychiatric pharmaceuticals that are excreted in human urine and survive wastewater treatment plant processes, scientists told a meeting in Boston of the American Association for the Advancement of Science.

For the experiment, scientists divided 75 wild European perch into three groups. One group lived in clean water. The second group's water had low concentrations of Oxazepam, a commonly prescribed medication used to treat anxiety in humans.

The concentration was similar to what is found in waterways downstream from sewage treatment plants.

The third group's water had 500 times the amount of Oxazepam typically found in waterways. After a week, the fish were subjected to routine behavioral tests.

'Before we exposed the perch to the drug they were all very shy. They were not taking any risks at all basically. After exposure, they were swimming around much more, like they were unconcerned, and they were not as social. They just wanted to swim on their own. Some even avoided schools as much as possible,' lead researcher Tomas Brodin, also with Umea University, told Reuters.

Fish exposed to Oxazepam also became more aggressive feeders, he said.

'I have no doubt that the behavioral effects we see are true and that they are potentially going on as we speak,' Brodin said.

'This is a global issue,' he added. 'We find these concentrations (of psychiatric drugs) or close to them, all over the world.'

The scientists plan to expand the study to look at the wider ecological effects of Oxazepam and to understand on a molecular level what happens to perch that are exposed to the drug.

The research appears in this week's Science magazine.

(Reporting by Irene Klotz; Editing by Tom Brown, Toni Reinhold)