Antidepressant pollution is altering fish behaviour

A study led by Monash University and the University of Tuscia has revealed how long-term exposure to pharmaceutical pollutants is dramatically altering fish behaviour, life history and reproductive traits.

The five-year investigation, focusing on wild-caught guppies exposed to the widely prescribed antidepressant fluoxetine (Prozac), highlights the profound and interconnected effects of this pollutant on aquatic ecosystems. The study has been published in the Journal of Animal Ecology.

Pharmaceutical pollutants, especially antidepressants like fluoxetine, have become a pervasive issue in water bodies worldwide. These pollutants, often introduced through wastewater discharge, persist at low levels in rivers, lakes and oceans — yet despite their widespread presence, the full impact of these chemicals on aquatic wildlife has remained unclear.

To explore the effects of antidepressant pollution, the research team exposed guppies to three environmentally relevant concentrations of fluoxetine over multiple generations. The team then meticulously tested fish behaviour, physical condition and reproductive health after five years of pollutant exposure. Male guppies were the focus due to their heightened sensitivity to environmental shifts, particularly in traits tied to behaviour, body condition and reproduction.

Fluoxetine exposure disrupted the natural correlations between key traits. For instance, the expected link between activity levels and body condition, and between the size of the gonopodium (a modified anal fin used as a reproductive organ) and sperm vitality, was altered. This disruption indicates that the pollutant is interfering with the natural trade-offs fish make between survival and reproduction.

“Even at low concentrations, fluoxetine altered the guppies’ body condition and increased the size of their gonopodium, while simultaneously reducing sperm velocity — an essential factor for reproductive success,” said study co-leader Dr Upama Aich, from Monash University.

“Fluoxetine exposure also significantly reduced the behavioural plasticity of guppies, leading to a lower capacity of the individuals to adjust their own activity and risk-taking behaviours across contexts,” added co-leader Assistant Professor Giovanni Polverino, from the University of Tuscia.

The research thus offers vital insights into how chronic exposure to common pharmaceutical pollutants like fluoxetine can fundamentally alter the traits that fish rely on for survival and reproduction. The findings highlight the need to address pharmaceutical pollution and implement stricter regulations to protect aquatic life from this threat.

“The disruption of behavioural plasticity and the altered correlations between critical traits could undermine fish populations’ ability to adapt to environmental challenges, threatening their long-term survival,” concluded senior author Professor Bob Wong, from Monash University.

Image credit: iStock.com/underworld111