The 8th International Symposium on Sturgeon (ISS8), Viyana, Avusturya, 10 - 15 September 2017, ss.1
Five species of sturgeons (Huso huso, Acipenser gueldenstaedtii, A. nudiventris, A.stellatus and A. Sturio) were abundant in Turkish waters until the middle of 20th century but following a drastic decline since the 1960s, they are critically endangered despite several attempts to regulate directed fisheries and bycatch.
The major impact upon the sturgeon populations is the management of freshwater resources in Turkey witnessing an immense pressure to produce energy through the installation of hydropower facilities. This development data destroyed the potential of three of the five historic sturgeon rivers (Yesilirmak, Kirilirmak and Coruh) due to the restriction of access of spawners to the lower 20-40 km. Also in Sakarya River, the second longest river in Turkey with approx. 700 km hydrodevelopment started in the 1960s but focused on the middle and upstream regions of the Anatolia mountains, leaving 200 km of the river freely accessible until 2012. Under these altered conditions, only A. gueldenstaedtii and A. stellatus were able to still reproduce in the river.
Additional development of Hydroelectric Power Plants (HEPP) was started in 1986 when the Pamokova HEPP was constructed 150 km from the sea. In 2012 the construction of 3 additional HEPPs (Doğançay I-II and Adasu) started in the river section below Pamokova, further reducing the remaining section of the free flowing river to approx. 70 km. While fish passage facilities were included in the construction of the HEPPs their design and location as well as the hydrological characteristis and the maintenance render them completely dysfunctional. In addition, downstream migration was entirely ignored during the planning and construction.
A survey was carried out in the remaining free flowing section of the river below Adasu HEPP in 2014 to determine fish community composition, water quality and macro invertebrate fauna at 4 stations.
While A. gueldenstaedtii YOY were not observed in the river following the construction of the latter 3 dams, A. stellatus still was observed to reproduce in the remaining river section, as was revealed by catches of 25g juveniles in 2014. Recently, two more new HEPPs are planned on remaining section of Sakarya River. As such less than 40 km distance between the last dam and the sea will be detrimental for the last sturgeon population reproducing in the Sakarya River.