Variation in the habitat Suitability indices of Chondrostoma regium (Leuciscidae) in Zab River during four seasons

In the conservation programs of aquatic ecosystems and fish stocks, understanding of the habitat preferences of aquatic species play an important role. In this regard, the study was aimed to investigate the habitat preference and habitat suitability index (HSI) of Chondrostoma regium in its distribution range in Zab River. A number of environmental variables, including pH, temperature, EC, TDS, elevation, water depth, river width, river slope, flow velocity, and substrate type, along with the abundance of C. regium at 6 stations (each with three replication) from the downstream to upstream were recorded seasonally from the fall of 2021 to the summer of 2022. The results showed that habitat suitability of C. regium is different in four seasons and this species prefers habitats with pH in a range 9-10, high temperature, low altitude, low bed slope, moderate velocity, and gravel and slate beds without vegetation, and these environmental factors were almost similar during the four seasons of the year. But EC, TDS, river width and water depth preferences were different in different seasons. In spring, it prefers with greater width and depth, and in summer and autumn, habitats with lower width and depth. EC and TDS were lower in spring and summer and relatively higher in autumn and winter due to seasonal changes. In general conclusion, the little Zab River is moderately suitable for C. regium.