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 S. cephalus samples were found to range between I-VIII; in addition, 153 of them were female and 89 were male. Their fork lengths changed between 114-332 mm, and body weights were between 22.5 and 550.3 g. 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 114 mm of fork length and 27.3 g, while the smallest male at sexual maturity had 118 mm of fork length and 24.2 g. The mean gonadosomatic index of male and female specimens were found highest 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 mu m and 1900 mu m. The egg number in per one gram ovary was maximum in August, and minimum in April and May. S. cephalus 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 151302 in the specimen at the age of VI.