Ergönül, Mehmet Borga2021-12-022021-12-022020http://hdl.handle.net/20.500.12575/76620Most of the ichthyological research in Turkish freshwaters are focused on large rivers. However, the fish fauna of small karst-springs is neglected. In such small karst-fed streams the downstream end of the underground flow reaches the surface and drain to the sea in a very short distance. In this study, the fish fauna of a karst-fed small stream, Özlen Stream, was investigated on a seasonal basis. A total of 8 fish species (Anguilla anguilla, Carassius gibelio, Squalius fellowesi, Oncorhynchus mykiss, Gambusia holbrooki, Mugil cephalus, Liza saliens and Salaria fluviatilis) were identified. Three of these fish species are exotic and invasive for Turkish freshwaters. C. gibelio and G. holbrooki, are considered a serious threat to natural fish populations in Turkey. Presence of such invasive fish species even in a small river indicates that they are expanding their distribution area in Turkey.enKarst springInvasiveEşen RiverMosquito fishArticle2902