Pharmaceutical pollution in waterways is having a "disturbing impact" on fish, according to new research.
Psychoactive drugs - including antidepressants - are altering the reproductive behaviour, anxiety levels, and anti-predator responses of fish in the wild, according to Australia's Monash University.
The findings of the impact on the social behaviour of fish has been published in the journal Biology Today.
Dr Jake Martin, from the university's school of biological sciences, said: "Our research found that the antidepressant pollutant fluoxetine (commonly marketed as Prozac) did not alter behaviour of solitary fish.
"But in a group setting, fluoxetine exposure disrupted the frequency of aggressive interactions and food consumption."