fish assemblages as influenced by environmental factors in taleghan river (the caspian sea basin, alborz province, iran)

the relationship between some habitat factors and fish assemblage was analyzed in the taleghan river, alborz province, iran. fish specimens from thirty-three sites were sampled by electrofishing device in october 2014. the habitat parameters, including elevation (m), water depth (cm), river width (m), river slope (%), current velocity (m.s-1), number of large stone (> 15 cm), average stone diameter (cm), substrate index (si%), level of potamal cover, level of periphyton cover, ph, electrical conductivity, total dissolved solid and temperature (°c) were measured in all sampling sites. canonical correspondence analysis was performed to study the relationship between fish assemblage and environmental factors. the results showed that the fish assemblages of the taleghan river are organized by the environmental variables. based on the results, the abundance of c. gracilis did not show any distinctive relationship with examined habitat variables, whereas the presence and abundance of b. cyri showed a rise with increasing substrate index and bed stone diameter and a decline with increasing river width and flow velocity. the presence and abundance of o. bergianus rises with the increasing current velocity and river width and showed a decline with increasing slope, depth and substrate index. the results of this study provides insights into the ecology of fishes in the taleghan river and can help an effective fisheries management of other rivers of the caspian sea basin.