en Biology & physiology Biology & physiology پژوهشي Orginal research papers <span style="color: black font-family: "Times New Roman","serif" font-size: 12pt mso-fareast-font-family: "Times New Roman" mso-ansi-language: EN-US mso-fareast-language: TR mso-bidi-language: AR-SA">In this study, the reproductive biology of chub population in Hafik Lake was investigated. 242 samples were caught between April and November 2009. The age of <i>S. cephalus</i> samples were found to range between I-VIII in addition, 153 of them were female and 89 were male. Their fork lengths changed between 114-<st1:metricconverter w:st="on" productid="332 mm">332 mm</st1:metricconverter>, and body weights were between 22.5 and <st1:metricconverter w:st="on" productid="550.3 g">550.3 g</st1:metricconverter>. Male specimens were determined to reach sexual maturity at II and III age, while females reached at III and IV years of age. The smallest female individual at sexual maturity had <st1:metricconverter w:st="on" productid="114 mm">114 mm</st1:metricconverter> of fork length and <st1:metricconverter w:st="on" productid="27.3 g">27.3 g</st1:metricconverter>, while the smallest male at sexual maturity had <st1:metricconverter w:st="on" productid="118 mm">118 mm</st1:metricconverter> of fork length and <st1:metricconverter w:st="on" productid="24.2 g">24.2 g</st1:metricconverter>. The mean gonadosomatic index of male and female specimens were found highest<font size="3"><font face="Times New Roman"><span style="mso-spacerun: yes"> </span>in April (12.33, 8.02) and May (8.37, 4.64) and minimum in August (2.39, 1.22). Egg diameters of chub individuals were measured between 343 µm and 1900 µm. The egg number in per one gram ovary was maximum in August, and minimum in April and May.<i> S. cephalus</i> was determined to lay eggs in Hafik Lake towards the end of April, which continued until the end of July. Maximum fecundity in population was observed as <st1:metricconverter w:st="on" productid="151302 in">151302 in</st1:metricconverter> the specimen at the age of VI.</font></font><a name="0.1_OLE_LINK5"></a><a name="0.1_OLE_LINK6"></a> </span> Chub, gonad development, Hafik Lake 681 692 http://jifro.ir/browse.php?a_code=A-10-1-189&slc_lang=en&sid=1 B. Unver bunver@cumhuriyet.edu.tr 10031947532846004269 10031947532846004269 Yes s. Kekilli 10031947532846004270 10031947532846004270 No