Present Status of Sturgeon in the Lower Sakarya River in Turkey

Abstract

The Hydro development started in the 1960s with building 3 major dams in the upstream section of the Sakarya River. During the 1980s the development of the floodplain sections of the river had its onset. Under these altered conditions Huso huso, Acipenser nudiventris, and Acipenser sturio disappeared from the river until the 1980s but Acipenser gueldenstaedtii, as well as Acipenser stellatus, were shown to still reproduce in the remaining section of the river by 2013. The construction of three additional HEPPs begun in the river section below Pamukova, blocking migration and cutting off major spawning sites. While fish passage facilities were included in the construction of the HEPPs since the 1980s, their design and location, as well as the maintenance rendered them completely dysfunctional. A survey was carried out in the remaining free flowing section of the lower river in 2014 to determine fish community composition and water quality at 4 stations below Adasu HEPP. While a few A. gueldenstaedtii juveniles were observed in Sakarya River mouth close to the Black Sea, only one young-of-the-(YOY) (A. stellatus; W:25g; TL:28cm) was reported which was captured from the Lower Sakarya River.

Genetic population structure of the critically endangered stellate sturgeon (Acipenser stellatus) in the Black Sea basin: Implications for conservation

“…Owing to the specific water current characteristics in the southern part of the Black Sea (Shapiro, 2009), it is difficult to specify which of these rivers is home to the orange cluster individuals. The presence of stellate sturgeon young‐of‐the‐year in the lower section of the Sakarya River was also reported by Memiş et al (2019, 2020). However, based on population structure, all of the individuals sampled in the proximity of the Sakarya River showed signs of admixture.…”

“…The reduction of the effective population size of all sturgeon species in the Black Sea is widely recognized. It is attributed to a series of stressors such as historical overharvesting, habitat loss and a high disruption of the main migration routes in the spawning rivers (Ustaoğlu & Okumuş, 2004; Suciu & Guti, 2012; Memiş et al, 2019). The impact of such stressors on the sturgeon population of the Black Sea remains largely unquantified.…”

“…Very rare radiation points (only three in Figure S1) with one mutation step between haplotypes identified in the NW-BS region indicate a slight sign of a post-bottleneck recovery in the NW-BS region (Raupach et al, 2010;Mayoke et al, 2020) The reduction of the effective population size of all sturgeon species in the Black Sea is widely recognized. It is attributed to a series of stressors such as historical overharvesting, habitat loss and a high disruption of the main migration routes in the spawning rivers (Ustao glu & Okumus ¸, 2004;Memis ¸et al, 2019).…”

“…No spawning event was reported based on a larvae and juveniles survey, although adult sturgeons were found in the Yes ¸ilırmak River. For the Kızılırmak River, no data are available (Zengin et al, 2010), whereas, in the Sakarya River, reproduction was confirmed by capturing one young-of-the-year stellate sturgeon in the lower section of the river (Memis ¸et al, 2019(Memis ¸et al, , 2020.…”

Some Growth Parameters of Five Fish Species in the Lower Sakarya River, Turkey

“…Various researches have been carried out on the fish species living in the Sakarya River and its tributaries. (Ölmez, 1992;Emiroğlu, 2011;Kahraman, Göktürk & Aydın, 2014;Korkmaz & Zencir Tanır, 2016;Memiş, Tosun, Yamaner, Tunçelli & Gessner, 2019;Reis, Cerim & Ateş, 2019).…”