Sampling was carried out on a seasonal basis during 2007–2009, using a conventional bottom trawl net with 44 mm codend mesh size in Izmir Bay, Aegean Sea. A total of 116 valid hauls: 27 in autumn, 28 in winter, 35 in spring and 26 in summer, were conducted at depths ranging from 30 to 70 m. A total of 112 species: 15 Chondrichthyes, 83 Osteichthyes, 11 Cephalopoda and 3 Crustacea were obtained in the trawl codend. All captures were separated into commercial (C) and non-commercial (NC) species. The C ratio was 69.6%, while NC (i.e. discards) was 30.4%. Diplodus annularis was the most abundant species in all seasons, followed by Mullus barbatus, Merluccius merluccius, Citharus linguatula, Serranus hepatus, Lepidotrigla cavillone, Spicara maena, Myliobatis aquila, Diplodus vulgaris, and Trisopterus minutus in decreasing order of abundance. These top ten species constituted 75% of total catch weight. Biomass ratios of total discards to commercial species were 0.44 : 1.