Age Structure and Growth Rate of Rutilus frisii kutum (Kamensky, 1901) Population in Vali Abad River (Southern Caspian Sea), Iran

Age is one of the most important biological aspects of fish, and the lack of accurate information on the age of many fish species leads to inappropriate management policies [1]. Growth phenomenon is also one of the most key biological aspects of fish in the population, which exhibits the type of adaptation to environmental conditions [2]. The kutum in the Caspian Sea (Rutilus frisii kutum) belong to the Cyprinidae family [3]. This species can be found all along the southern coast of the Caspian Sea from the river Atrak to the Kora. Vali Abad River, one of the tributaries of Cheshmeh Kileh River, flows in the southeast of Tonekabon city center. It is rain-fed and flows from west to east. The river has a length of 14 km, an average bed slope of 0.7% and flows in bicarbonate and bicarbonate sulfate areas [4]. Many kutums migrate to the Shiroud, Vali Abad, Hawiq, Lemir, Anzali, Sefidrood, Tajan, Babolrood and Gorganrood Rivers to reproduce in the coasts of Iran [5]. Terms of catch and extraction, kutums is one of the most valuable fisheries in the Caspian Sea and contributes more than half of the total catch of bony fish [6]. Overall, 90% of its resources comes from Iran [7]. This fish with its high economic value in the southern shores of the Caspian Sea which depends on conservation [8].