habitat suitability index of barbus cyri (heckel, 1843) in tootkabon river, the south caspian sea basin, iran

knowledge of habitat requirements of aquatic animals plays an important role in fisheries and protection programs of aquatic ecosystems. hence, this study was conducted to investigate the suitability indexes of habitat use and habitat suitability index (hsi) of barbus cyri in its distribution range in tootkabon river. a number of environmental variables, including elevation, water depth, river width, river slope, velocity, substrate type, and average diameter of bed stone, riparian vegetation type and the relative abundance of b. cyri at 13 stations and three replications from the downstream to upstream were examined during november 2013.  the results showed that b. cyri mostly selects upper stretches of the river with higher velocity, middle depth, lower width and bed rock substrate i.e. bed with boulder cover and grasslands and also its residential area is of riparian type compared with the available ranges. habitat selectivity index for b. cyri showed that the elevation is 130-220 m, water depth 18-75 cm, channel width less than 12 m, channel slope 0.5-2.3%, water velocity less than 0.8 m.s-1, bed rock substrate, average diameter of bed stone larger 15-50cm. presence of these conditions with hsi of 0.798 indicates that tootkabon river is an excellent habitat for b. cyri.