PostprintThis is the accepted version of a paper published in Aquatic Toxicology. This paper has been peerreviewed but does not include the final publisher proof-corrections or journal pagination.Citation for the original published paper (version of record):Kellner, M., Porseryd, T., Porsch-Hallstrom, I., Hansen, S., Olsén, H. (2015) Environmentally relevant concentrations of citalopram partially inhibit feeding in the three-spine stickleback (Gasterosteus aculeatus).Aquatic Toxicology,[158][159][160][161][162][163][164][165][166][167][168][169][170] http://dx.doi.org/10.1016/j.aquatox. 2014.11.003 Access to the published version may require subscription. N.B. When citing this work, cite the original published paper. NOTICE: this is the author's version of a work that was accepted for publication in Aquatic Toxicology. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Aquatic Toxicology, Vol. 158,[165][166][167][168][169][170] Abstract Selective Serotonin Re-uptake Inhibitors (SSRI) are mood-altering, psychotropic drugs commonly used in the treatment of depression and other psychological illnesses. Many of them are poorly degraded in sewage treatment plants and enter the environment unaltered. In laboratory studies, they have been demonstrated to affect a wide range of behaviours in aquatic organisms. In this study we investigated the effect of a three week exposure of 0.15 and 1.5 µg/l of the SSRI citalopram dissolved in the ambient water on the feeding behaviour in three-spine stickleback (Gasterosteus aculeatus). Feeding, measured as the number of attacks performed on a piece of frozen bloodworms during a 10 minute period, was reduced by 40-60% in fish exposed to both 0.15 and 1.5 µg/l citalopram. The effects of the environmentally relevant dose 0.15 µg/l on feeding, an important fitness characteristic, suggests that the ecological significance of environmental SSRI exposure may be pronounced.