Effects of a common antidepressant on behavior and dispersal in the globally invasive freshwater eastern mosquitofish (Gambusia holbrooki)

Anthropogenic pollutants are an ongoing problem in aquatic environments. One such pollutant is fluoxetine, a selective serotonin reuptake inhibitor commonly known by the brand name Prozac. We still do not fully understand how such medical wastes affect aquatic organisms, specifically, how they affect traits that are important to the ecology and evolution of populations and species. We examined how chronic exposure to a field-relevant concentration of fluoxetine (440 ng/L) affects different behaviors in wild-caught Gambusia holbrooki. We tested fish social behavior, cognitive flexibility, and tendency to disperse in an artificial stream. We found that exposure to fluoxetine did not affect performance in any of the aforementioned behavioral assays. Furthermore, neither sociability nor cognitive flexibility predicted movement in the dispersal assay. At least for G. holbrooki, it appears that fluoxetine may not have large effects on the tested predictive behaviors or dispersal itself. While these results suggest that fluoxetine exposure may have limited effects on a key trait important in ecology and evolution—namely dispersal—it may still affect other traits not tested in this study.