The aim of this study is to determine the effects of red mullet gillnets that commonly used in Turkish waters on sustainability of non target fish species. For these purpose, surveys were realized with 18 - 20 - 22 mm nominal bar length red mullet gillnets between December 2008 and May 2010 along the north Aegean Sea coasts (5-30 m). SELECT method was used with five different model (Normal location, normal scale, log-normal, gamma and bi-modal) for evaluating selectivity parameters of non target fish species. Selectivity models were determined as bi-modal for Serranus scriba and Symphodus tinca, log normal for Scorpaena porcus and Spicara maena and gamma for Pagellus acarne. Optimum catch lengths and spread values and selectivity curves were given for 5 species. Results showed that use of a larger mesh size over the 22 mm mesh is important for ensuring stock sustainability of the non target fish species.