en Biology & physiology Biology & physiology پژوهشي Orginal research papers <span lang="TR" style="font-size:11.0pt"><span calibri="" style="font-family:"><span style="color:black">A study on the feeding and reproductive habits of the Caspian roach (<i>Rutilus caspicus</i>) in Iranian waters was conducted from April 2016 to March 2017. The stomach contents of 330 specimens were analyzed and 104 specimens were chosen for detailed investigation. Of these, 47 had empty stomachs, and 57 contained food. The stomach emptiness index peaked in winter (73%) and was lowest in spring (11%). Gastropods were identified as the primary food source, alongside crabs, bivalves, and plant fragments.</span></span></span> <span lang="TR" style="font-size:11.0pt"><span calibri="" style="font-family:"><span style="color:black">Reproductive analysis showed the largest mean ovum diameter (1.501&plusmn;0.1 mm) at age 4 and the smallest (0.76&plusmn;0.15 mm) at age 2. The gonadosomatic index (GSI) in females ranged from 0.05 to 0.10, with spawning beginning in March and lasting until mid-spring. The mean absolute fecundity was 19,469 eggs, with 50% of females reaching maturity at 138 mm and males at 125 mm.</span></span></span> <span lang="TR" style="font-size:11.0pt"><span calibri="" style="font-family:"><span style="color:black">A significant linear relationship was observed between fork length, weight, and absolute fecundity (<i>p</i><0.05).</span></span></span> <span lang="TR" style="font-size:11.0pt"><span calibri="" style="font-family:"><span style="color:black">This research provides valuable insights into the seasonal diet, reproductive biology, and ecological behavior of <i>R. caspicus</i>. The findings are crucial for understanding the species&rsquo; role in the Caspian Sea ecosystem and informing its management and conservation.</span></span></span> Rutilus caspicus, Feeding habits, Nutrition, Fecundity, Caspian Sea 837 852 http://jifro.ir/browse.php?a_code=A-10-5085-2&slc_lang=en&sid=1 E. Hajiradkouchak eisahajirad@gmail.com 100319475328460056840 100319475328460056840 Yes Caspian Sea Ecology Research Center B. Rahnama rahnama.behzad@gmail.com 100319475328460056841 100319475328460056841 No Caspian Sea Ecology Research Center H. Fazli hn_fazli@yahoo.com 100319475328460056842 100319475328460056842 No Caspian Sea Ecology Research Center H. Raeisi raeisi_hadi@yahoo.com 100319475328460056843 100319475328460056843 No University of Gonbad kavous F. Radfar rahnama.behzad@gmail.com 100319475328460056844 100319475328460056844 No Caspian Sea Ecology Research Center