The topmouth gudgeon is a small freshwater cyprinid fish, originating from Eastern Asia. It was introduced to Europe in the early 1960’s and has since then spread all over the continent. It is considered as one of the most invasive species worldwide. Both human translocation (aquaculture and recreational fishing) and natural dispersion through streams and rivers facilitate its ongoing dispersal. Its success as an invasive species is explained by its non-selective food choice, multiple spawning , parental care and its ability to cope with extreme habitat conditions. It prefers standing waters rich in submerged vegetation. Topmouth gudgeon is considered a pest as it outcompetes native species and also serves as a vector for a deadly parasite (Sphaerothecum destruens). As a consequence of infection with this parasite, populations of native fish species are known to become extirpated.