Importance of protecting the natural reproduction of kutum (Rutilus kutum Kamenskii, 1901) in exploiting the ecological carring capacity of the ecosystem

251 specimens of kutum fish caught by bony fish persine on the southern shores of the Caspian Sea (Mazandaran) during the years 2017-2019 were studied to study the growth trend of this species. In this study, maximum estimated length (L∞) and annual growth coefficient (K) of kutum fish were estimated 71.79 cm and 0.13, respectively. The results of natural reproduction of this species in Kheirud river with a length of 2 km showed that in 2017-2018, more than 30,000 breeders (female) of anadromous fish migrated to Kheirud river for reproduction and more than 97% of it were kutum fish. As a result of this study, more than 525,000 kutum fish fry were produced and prepared to migrate to sea. (2017-2018). The results showed that the partnerships of fishermen and local rural communities can have a positive effect on the natural reproduction Influence coefficient of kutum fish (P <0.05). The results showed that the penetration coefficient (effectiveness) of fishermen (35%) and rural women (30%) ) were more than the students' effectiveness (16.7) (P <0.05). Thus, by protecting the natural reproduction of kutum fish, other species of anadromous fish have reproductive successes in the Kheirud river, which will establish the desired ecological balance and exploit the ecological carring capacity of the ecosystem.