The role and significance of some environmental parameters on fish biodiversity in Roodbabol River (Mazandaran Province)

To investigate fish biodiversity indexes of Roodbabol River and their relationships with environmental factors, sampling was conducted at 20 stations. At each sampling station factors including river depth, river width, water velocity, substrate rubble diameter, temperature, dissolved oxygen, electrical conductivity and altitude were measured. 6 freshwater fish species has been recorded namely Barbus (Luciobarbus capito), Hiircan Crested Loach (Paracobitis hircanica), Iranian Goby (Ponticola iranicus), Tabarestan Spirlin (Alburnoides tabarestanensis), Grass Carp (Ctenopharyngoden idella), Crucian Carp (Carassius carassius), and Rainbow Trout (Oncorhynchus mykiss). Shanon diversity and Simpson dominance indexes were the highest at station 6 (H′= 1.068 and λ = 0.6071) and 7 (H′= 1.212 and λ = 0.6653) and the lowest at station 9 (H′= 0.103, λ = 0.041). Stations 7 and 13 were the richest stations for species richness index (0.9705 and 0.8736, respectively) while stations 9 and 11 showed the lowest species richness (0.2597 and 0.2153, respectively). The most and least values of Pielou′s evenness index were observed at stations 11 and 20 (0.9816 and 0.3435, respectively). Water temperature with fish abundance, Margalof, Shannon diversity and Simpson dominance indexes, river depth with fish species number, and river width with Pielou′s index had positive and significant correlation. In addition, a significant and negative correlation was discovered between electrical conductivity with Margalof index and between river width with fish abundance. PCA indicated that factors like depth, velocity, rubble diameter and river width primarily and other factors of altitude, salinity and shadow level secondly affect some fish species abundance in particular stations.