An updated checklist of fishes of the Caspian Sea basin of Iran with a note on their zoogeography

Although the Southern Caspian Sea basin (SCSB) fish fauna has been studied for more than 200 years, new species continue to be discovered, reported and renamed. Here we take the opportunity to provide a new and updated checklist of the fishes of the southern Caspian Sea basin. The list is based on historical literature records and taxon occurrence data obtained from natural history collections and new fish collections. A total of 119 species belong to 63 genera, 18 families, 16 orders and two classes are listed. Exotic fishes comprise 19 species in seven families. The number of species is higher than two published checklists in 1988 (74 species and 42 genera) and in 2010 (116 confirmed species belonging to 61 genera and 18 families). The fish taxa were classified into four major groups based on the fish origin, ecoregion and ecological factors (tolerance to salt water and mode of life). Two species were new to science described since 2010, the taxonomic status of some species has been changed and some subspecies has got full specie rank. In general, the ancient origins of the south Caspian Sea (being part of Paratethys basin), the role of closing of the Tethys Sea, being important glacial refugia and colonization sources, long history of connection and isolation from fresh and marine waters, multiple sources of species, wide latitudinal extent, uneven distribution of inflows and nutrient inputs, and low to moderate salinity, different habitat types (both fresh and brackish habitats, rivers, lakes, lagoons, marshes, and marine environments), have all contributed to the high ichthyodiversity of the southern Caspian Sea basin.