The determinant factors underlying habitat selectivity and preference for Black fish Capoeta capoeta gracilis (Keyserling 1891) in Siyahrud River (a tributary of Sefidrud River basin)

Abstract

Understanding habitat requirements of aquatic organisms is key factor for sustainable exploitation and biodiversity conservation of riverine ecosystems. The habitat preference in fish has extremely important for the management of fish populations. The habitat requirements of Black fish (Capoeta capoeta gracilis) in Siyahrud River -tributaries of the Sefidrud River in Caspian basin- were studied in 13 stations along the river during October to November 2013. Hydrological characteristics of the river including water velocity, depth and width, slope, altitude, type of substrate materials, and plant coverage were recorded for each station. Ranges of habitat use and habitat selectivity with regard to the availability of habitat units for different variables were measured using HABSEL software. Despite significant correlation between the water velocity and depth, results from multiple regressions showed preference for the depth range of 17 to 38 cm. The results showed that behavioral preference in C. capoeta gracilis for the velocity was between 0.44 and 0.56 m/s. Also, specimens tended to be present in cobble stone substrate. Therefore, the anthropogenic activities over the Siyahrod River changing the river width, depth, substrate and the flow rate may affect the presence and distribution of C. capoeta gracilis in the mentioned river.