The difference in response to some environmental variables by two sympatric species, Garra rufa (Heckel, 1843) and Garra gymnothorax Berg, 1949

Understanding the optimal habitat of species, especially closely related species, can help in their better management and protection. For this purpose, in the present study, the response of two sympatric species, Garra rufa and Garra gymnothorax, to some environmental variables and the differences between them were analyzed. In this regard, the effect of six habitat variables including the width (m) and depth (cm) of the river, water current velocity (ms-1), altitude (m), temperature (°C) and substrate index evaluated on the Habitat Suitability Criteria (HSC) pattern in 27 study reach, almost in the entire distribution range of these two species. The results showed that G. rufa lives in rivers with width <40 m, depth <45 cm, temperature >22 °C, substrate index 3.5 - 6.5, and depending on the conditions, water current velocity less than 0.45 or more than 1.2 ms-1, which are located at an altitude between 600 and 1000 m, while G. gymnothorax prefere habitats with width <10 m, depth <150 cm, temperature >24 °C, substrate index >4.5, water current velocity <1.05 ms-1 located at an altitude >400 m. The analysis shows that the G. gymnothorax has a smaller range of favorability than G. rufa for all six habitat variables studied, which it somehow indicates its narrower ecological niche and the greater vulnerability of this species to changing environmental conditions. The wider distribution of G. rufa may contribute to the ability to maintain larger populations of this species. This wider presence of the species not only helps to facilitate autecology processes but also increases the probability of survival in case of local environmental disturbances. The results of this study can help in determining the protection priorities for both species.