Background. The Izmir nase, Chondrostoma holmwoodii (Boulenger, 1896), an endemic species for the inland waters of Turkey, is in the category of DD “Data Deficient” in the list of IUCN Red Data Book. There are insufficient data on the biological characteristics of the species in the literature. The aim of this study was to obtain the growth characteristics of Izmir nase population from Western Anatolia and compare them with the previous data reported in literature. Materials and methods. Biological features of Izmir nase were examined based on a total of 1208 specimens collected from Tahtali Dam Lake during the period May 2006–April 2007. Age of fish was determined by reading scales. Length–weight relation and the von Bertalanffy equationwere used to evaluate the fish growth. Results. Scales reading indicated the presence of 5 age classes. The computed growth parameters were: L∞ = 29.19 cm, k = 0.177· year–1 and t0 = –3.258 year–1 for both sexes. The length-weight relations were estimated as W = 0.019L2.97, W = 0.012L3.11 and W = 0.011L3.13 for females, males, and both sexes combined, respectively. Conclusion. The Izmir nase from Tahtali Dam Lake was characterized by linear growth and it was observed that the fish grew faster during the first two years. Many endemic fish species in inland waters of Turkey are under the threat of extinction due to human activities (pollution, drought, dam construction, habitat degradation, and overfishing) but the species is not threatened by these factors in the study area.

growth, population structure, Chondrostoma holmwoodii, Izmir nase,Tahtali Dam Lake