Occurrence of Gambusia holbrooki Girard, 1859 (Poeciliidae)in Four Mediterranean River Estuaries of Turkey, Nursery Habitats of Several Native and Threatened Species

The aim of this study is to report the occurrence of the invasive alien Eastern mosquitofish Gambusia holbrooki in four Mediterranean river estuaries of Turkey (Manavgat, Goksu, Seyhan, and Ceyhan). The monitoring of fish communities carried out from 2014 to 2017 revealed the presence of G. holbrooki both with juveniles and adult specimens in all four estuaries. Along with G. holbrooki and other alien species a total of 24 native species at juvenile stages were recorded. Some of them, such as the critically endangered Anguilla anguilla and the endemic goby Pomatoschistus anatoliae, are of particular conservation interest and require specific attention. The presence of G. holbrooki in the studied estuaries that could serve as recruitment areas for the populations of the sensitive native and threatened species may act as additional threat for their survival and may distort the ecological equilibrium of the river estuary ecotones.