Abstract
The Ilisu Dam is a large hydroelectric power plant that started to collect water in 2019 on the Tigris River in Turkey. This study was done during the period 2010 to 2014 to determine fish fauna of the Tigris River and its tributaries related to the potential reservoir area of the Ilisu Dam before its foundation. 35 fish species belonging to 10 families have been identified in the main river and its tributaries to be covered by the dam reservoir. One of these species, Glyptothorax steindachneri was recorded for the first time from the Turkish part of the Tigris River. 22 species were found widely distributed. At least 16 species were found to be endemic to the Tigris and Euphrates basins. Three species were already recommended with some level of international protection as per IUCN Red List. Cobitis kellei and Paraschistura chrysicristinae species, whose type localities were reported as upper Tigris, were not recorded.