Effects of water temperature and migration time on some fecundity indices and fertilization rate of female Kutum, Rutilus frisii kutum, migratory to Shiroud River in the southwest Caspian Sea

Kutum, Rutilus frisii kutum, is an commercially important fish in the Caspian Sea. The fish enters the rivers leading to the Caspian Sea for spawning. One of these rivers is Shiroud River. In the artificial propagation process of Kutum, different factors are involved in quality and quantity of female broods eggs and also in the best temperature and migration time for spawning. The influence of temperature and migration time on some fecundity indices and fertilization rate of female kutum in Shiroud River was studied in the spawning season. In this study, 90 individual females were studied from February to May 2007. Averages of total length, weight and age were 43.26 cm, 832.08 g, and 4.41 respectively. Results showed that maximum egg diameter (1.86 mm), number of eggs per each gram of body weight (309.12), relative fecundity (56.21) and fertilization rate (95.82 %) were obtained from 5 to 20 April (15.95?C). Maximum ovary weight (201.00 g) and absolute fecundity of eggs (49987.18) were obtained from 6 to 20 March (17.74?C). Relationship between temperature and migration time and fecundity indices was linear and weak.