Quietly invading the Balkans: Economidichthys pygmaeus (Holly, 1929) (Gobiidae) established in Northeastern Greece.

This study reports on a new translocated population of the Western Greece Goby (Economidichthys pygmaeus Holly, 1929) within the Thrace freshwater ecoregion in Northeastern Greece, approximately 370 km east of the species' native range (Ionian freshwater ecoregion; Western Greece). Specimens were identified by morphological examination and molecular confirmation. Based on a literature review and anecdotal information the Western Greece Goby was possibly introduced within the last two to five years, perhaps associated with fish farm imports from Western Greece. Population characteristics of the species in the new locations indicate that the species is fully established within an important biodiversity hotspot, the Aggitis sub-basin of the Strymon River, a transboundary river shared with Greece, Bulgaria and North Macedonia. This record represents the easternmost range expansion of the Western Greece Goby. In addition, it confirms a noticeable trend of expansion of this species since it has been also documented in the Southeastern Adriatic (Albania, North Macedonia) and the Western Aegean (southern Greece) during the last decade. This introduction may trigger ecological consequences, including the homogenization of formerly isolated ichthyofaunas. [ABSTRACT FROM AUTHOR]