Fish diversity and distribution in two protected rivers, Sardabrud and Chalus, southern Caspian Sea basin, Iran

Fish species diversity, distribution and abundance were studied in the Sardabrud and Chalus rivers, in the Southern Caspian Sea Basin, during 1992 and 1993 in five and four stations respectively, by monthly collections using electrofishing device. In total, 3200 fish specimens, including 15 species in Sardabrud River and 12 species in Chalus River, were investigated. The fish comprised of 13 genera and 5 families: Petromyzontidae, Cyprinidae, Cobitidae, Salmonidae and Gobiidae; the majority being Cyprinidae. This is the first report of Pseudorasbora parva in Sardabrud River. The Shanon’s index for Sardabrud River ranged from 0 to 1.77 and for Chalus River from 0 to 1.91. Fish species diversity was significantly correlated with altitude (r2= 0.96 and P< 0.01). The species diversity increases as one moves from the headstream towards the estuaries of the two studied rivers. Species diversity was independent of position but dependent on depth alone.