Calculating the habitat suitability index of Siahmahi (Capoeta buhsei, Kessler 1877) using the kernel smoothing in the Jajrood River, Namak basin of Iran

Fishes grow and survive in the habitats that have environmental essentials for living to fulfill their needs. The present study aimed to calculate habitat suitability index of Capoeta buhsei using the kernel smoothing in the Jajrood River. A method was provided to calculate the bandwidth needed for the kernel smoothing, i.e. 1000 band width (0-1000) were separately examined and the one with the lowest root mean square error was selected as the best. Nine environmental factors were measured: pH, temperature, EC, TDS, DO, depth, width of the river, water current velocity, and diameter of the substrate stones. The suitability curves were fitted. Four methods of calculating HSI were examined: arithmetic and geometric mean, maximum and minimum methods. This species preferred the habitats with fast water current, deep and wide areas of the river with low temperature having large stones. The first station (upstream) with a habitat suitability index of 0.796 was the most suitable living place for Capoeta buhsei in the Jajrood River.