Impacts of an anxiolytic drug on fish behaviour and habitat use in a natural landscape

Abstract

Pharmaceutical contaminants reaching natural aquatic ecosystems can affect fish behaviour, modifying activity patterns, foraging behaviour and antipredator responses. While laboratory-based studies can offer key insights, assessing the ecological relevance of these findings requires field-based approaches. Therefore, we examined the effects of oxazepam, a widely prescribed anxiolytic drug, on the behaviour of a cyprinid fish (the common roach, Rutilus rutilus) in the wild, combining slow-release exposure implants with continuous tracking via acoustic telemetry. To add ecological realism, we created a landscape of fear with an uneven distribution of resources (macrophytes) and exposure to predators (pike, Esox lucius), additionally testing the effects of the drug on roach habitat selection and predator-prey interactions. Fish exposed to the drug showed an increased swimming activity and speed, but exhibited a more constrained spatial distribution in the pond, favouring areas with higher refuge availability. Both exposed and unexposed fish modified their habitat use in the presence of predators. Exposed fish appeared to get closer to the predators when these were caged, but not when predators were free-roaming. Our findings highlight the importance of considering ecological context to understand how pharmaceuticals affect fish behaviour, which is crucial for assessing risks at population and ecosystem levels.

Keywords

predation; benzodiazepine; telemetry; home range; oxazepam; fish; behaviour

Published in

Proceedings of the Royal Society B: Biological Sciences
2025, volume: 292, number: 2054, article number: 20251443
Publisher: ROYAL SOC

SLU Authors

• Sandoval Herrera, Natalia

  • Department of Wildlife, Fish and Environmental Studies, Swedish University of Agricultural Sciences
    

• Mccallum, Erin

  • Department of Wildlife, Fish and Environmental Studies, Swedish University of Agricultural Sciences
    

• Cerveny, Daniel

  • Department of Wildlife, Fish and Environmental Studies, Swedish University of Agricultural Sciences
    
  • University of South Bohemia in České Budějovice

• Hellström, Gustav

  • Department of Wildlife, Fish and Environmental Studies, Swedish University of Agricultural Sciences
    

• Brodin, Tomas

  • Department of Wildlife, Fish and Environmental Studies, Swedish University of Agricultural Sciences
    

UKÄ Subject classification

Behavioral Sciences Biology
Environmental Sciences

Publication identifier

• DOI: https://doi.org/10.1098/rspb.2025.1443

Permanent link to this page (URI)

https://res.slu.se/id/publ/143782