en Ecology Ecology پژوهشي Orginal research papers The Aegean gudgeon <em>Gobio bulgaricus</em> (Drensky, 1926) is a freshwater fish species restricted to the western parts (Thrace) of Turkey. The aim of the present study is investigating key parameters such as age, growth, reproduction and feeding habits of <em>G. bulgaricus</em> in the Istranca Stream to determine biological characteristics of the species. During monthly samplings from March 2012 to June 2013, <em>G. bulgaricus</em> specimens were collected from the endorheic Istranca Stream, which is draining to the Lake Durusu in İstanbul. The results showed that the lifespan of the species was 5 years. The length&ndash;weight relationships of <em>G. bulgaricus</em> indicated positive allometric growth and the relationship was <em>ln</em>W=-3.976+3.080<em>ln</em>SL for females, <em>ln</em>W=-4.008+3.088<em>ln</em>SL for males and <em>ln</em>W=-4.049+3.118<em>ln</em>SL for all individuals. The mean size at first sexual maturity (L_m) was 4.03 cm SL for females and 3.94 cm SL for males. Absolute fecundity ranged from 355 to 5556 eggs with mean of 1179&plusmn;152 eggs. Prey analyses of digestive tract content indicated that <em>G. bulgaricus</em> was largely omnivorous (more precisely insectivorous) feeding mainly on aquatic insects and a small amount of plant and animal materials. Diptera larvae (IRI%=96.49) were the dominant prey of <em>G. bulgaricus</em> in terms of index of relative importance. It is considered that the present results will increase our knowledge of the life-history traits and feeding of <em>G. bulgaricus</em>. Age, Diet, Growth, Reproduction, Istranca Stream, Turkey 248 261 http://jifro.ir/browse.php?a_code=A-10-2582-1&slc_lang=en&sid=1 G. Saç gulsahsac@gmail.com 100319475328460032045 100319475328460032045 Yes Istanbul University, Department of Biology M. Özuluğ mozulu@istanbul.edu.tr 100319475328460032046 100319475328460032046 No Istanbul University, Department of Biology