The feeding habits of Kutum, Rutilus frisii kutum (Kamensky 1901), in the southern Caspian Sea (waters Mazandaran) were investigated by examining the stomach contents of fish collected monthly from the commercial and experiment catch from early October 2006 to September 2007. Their diet consisted different prey. Age determination, based on scale readings, showed that the population was composed of eight age- groups comprise to 1,2,3,4,5,6,7 and 8 years. The highest Index of Fullnes (IOF) was occurred in October for female (av.±SD) 313.86±65.9and 350.75 ±103.7 for male. The minimum IOF obtained in March, 119.42±59.21 and 144.07± 85.04 percent for female and male, respectively which coincided to spawning period. The significant different was between IOF and sex (at the female and male) in various months (ANOVA, P<0.05). Based on frequency of prey Cerastoderma lamarki was the main prey, Theodoxus sp. and Balanus improvisus as subordinate prey, and Rhithropanepeous harrisii, Hypanis sp., Neogobius sp., algae, scale and fish eggs as random prey in stomach contents of Kutum. The stomach contents of fingerling of Kutum with length groups <10cm were found Exuviaella cordata and Nitzchia distance of phytoplankton and Diatoma, and Nematoda of zooplankton groups. Based on Important Species Indices (ISI) C.lamarki was the important species in stomach content of Kutum which confirm frequency of prey analysis. The highest values condition factors (CF) were observed in April with 1.29±0.16 and lowest in September with 1.16±0.2. There is significant different between CF and various months (P<0.05). Consequently, the Kutum is a carnivorous species and commence feeding activity of animals from one-year old with Mysidae.