Fish on drugs - an experimental study of crucian carp exposed to fluoxetine and a natural predator

Abstract: Organisms in the aquatic environment face the challenge of exposure to environmental pollution by a multitude of pharmaceuticals. However, the potential for disruptive effects in non-target aquatic organism remains poorly understood. Fluoxetine is one of the most commonly prescribed psychoactive drugs and it has been shown to bioaccumulate in fish, and potentially affects a broad suite of important traits. Changes in fish morphology, behaviour and habitat use can have consequences at ecosystem level, since cascading effects can impact organisms of several trophic levels. Hence, a deeper understanding of potential responses of non-target organisms to fluoxetine exposure under various conditions is much needed. Here, I investigate single and combined effects of short-term exposure (c.a. 18 days) to two stressors; the anti-depressant fluoxetine and predation risk on three important fitness related traits (boldness, sociability and body weight) in the crucian carp (Carassius carassius), a common freshwater fish. My results show that exposure to fluoxetine at 100 µg L-1 significantly decreased propensity to take risks (boldness) in crucian carp, but I found no effects of fluoxetine exposure on sociability or body weight. Furthermore, no effects of exposure to a predator (pike) or any interactions between fluoxetine and predator exposure on any of the traits measured were detected. My data shows that a common anti-depressant drug frequently found in nature can alter important fitness related traits in a species known for its resilience to abiotic disturbances, and hence I stress the need for further studies. For society to recognise and fully understand negative impacts of pharmaceuticals on fresh water ecosystems, I for future studies suggest an ecosystem approach, where several species, stressors, key behavioural and morphological traits under varying environmental conditions are considered.