Distribution and diversity of fish from Seyhan, Ceyhan and Orontes river systems

In this study, the current ichthyofauna of the Seyhan, Ceyhan and Orontes River drainages were presented and actual taxonomic positions of the species were assessed. Sixty-seven species belonging to 32 genera and 17 families of fishes were reported from these river drainages in Turkey and Syria. Acanthobrama centisquama and Tinca tinca could not be observed in the study area and Alburnus sellal and Esox lucius are recorded for the first time respectively in the Lake Gölbaşı (connected to the Ceyhan River) and Seyhan River.


Introduction
The Orontes, Seyhan and Ceyhan rivers are some of the largest rivers in the northern Mediterranean Sea. The Seyhan and Ceyhan rivers form Turkey's largest delta plain, the Çukurova. These three river basins are host to many endemic species. Three of them can only be found in the Seyhan, seven of them only in the Ceyhan, and ten of them only in the Orontes. Their contribution to biodiversity is, without doubt, considerable. Several studies have been conducted on the distribution or/and taxonomy of fish species inhabited in the Seyhan, Ceyhan and Orontes rivers. Bostancı (2006) conducted the first ichthyofaunistic study in the area and revised the fish of these three rivers, after which Dağlı (2008) investigated only two northeastern tributaries of the Orontes River (streams Kınacık and Afrin). Kara et al. (2010) examined the fish of the upper and middle parts of the Ceyhan River. Erk'akan and Özdemir (2011) studied the fish of the Seyhan and Ceyhan rivers. Alagöz Ergüden and Göksu (2012) studied the fish in the Seyhan Dam Lake and Özcan (2013) researched a study on the ichthyofauna of the Orontes River. A recent study by İnal (2020) reported on the fish diversity and abundance in the Seyhan River estuary (Table 2). A comprehensive study has not yet reached the Orontes River in Syria. Unlike the research above, Geiger et al. (2014) conducted a comprehensive genetic study of the freshwater fish of the Mediterranean basin. Consequently showing different data.
Taxonomic problems have continued to increase while different researchers have conducted faunistic studies related to these rivers (e.g. identifies incorrectly or misrecords the species, see Table 2). This study aims to eliminate these ambiguities and reveal the actual taxonomic status of the species in the area; in addition, the rate of endemism in the region is determined.

Study area
The Ceyhan River originates from Pınarbaşı Village (Kahramanmaraş prov.). It forms a wide delta in Çukurova and pours into the Gulf of İskenderun in the Mediterranean Sea. Its main tributaries are the Söğütlü, Hurman, Göksun, Mağra Gözü, Fırnız, Tekir, Körsulu and Aksu streams. The Seyhan River has two important  Distribution in the area. Ceyhan River drainages and streams Çakıtsuyu-I, Üçürgesuyu-I (Seyhan River) in Turkey.
Distribution in the area. The lower part of the Orontes River drainage in Turkey; most probably it occurs also in Syria as the stream Afrin passes from Syrian territory (Feyhof and Turan 2019). Endemic to only the Orontes River.  Taxonomic notes. Alburnus qalilus (Krupp 1992) is distributed in the coastal streams in Syria. Birecikligil et al. (2016) reported A. qalilus from the Orontes River in Turkey. However,  revised the genus of Alburnus from the lower part of the Orontes and restricted A. qalilus to Syria.
Taxonomic notes. The genus of Salaria is represented with a single species Salaria fluviatilis in Turkey. This genus should be compared with different populations, which should be reviewed, both morphologically and molecularly, to clarify the taxonomy.

Discussion
As a result of this study, the current fish fauna conditions of the Orontes, Seyhan and Ceyhan rivers were evaluat-ed. Sixty-seven species belonging to 17 families of inland water fishes were reported from the Seyhan (28 species), Ceyhan (27 species) and Orontes (33 species) river drainages in Turkey and Syria. Almost all the fish species were recorded in the previous studies for the region, except Tinca tinca (see Table, 2). This species was reported from the Seyhan River (Erk'akan and Özdemir 2011;Ergüden Alagöz and Göksu 2012). The species' absence may be explained by the hunting method, habitat selection or season.
Acanthobrama centisquama was originally described from Orontes (Asi) drainage by Heckel (1843) but not recorded again for a long time . Then also this study period, this species could not be observed in this research area. It might be extinct or has a very localised distribution in the Orontes River.
Four species of Alburnus are known from the Seyhan, Ceyhan and Orontes rivers. Three of them have been obtained in the study period while A. adanensis has not been caught. Bostancı (2006) andErk'akan andÖzdemir (2011) identified an Alburnus species from the Seyhan River as A. adanensis. Birecikligil et al. (2016) reported that A. adanensis was s a synonym of A. sellal. Freyhof et al. (2018b) accepted A. adanensis as a valid species and  suggested that it might be extinct. Finally, Bektaş et al. (2020) have studied molecular characters of the genus Alburnus, and they recently treat as a synonym of A. kotschy.
Although the genus of the Cobitis has had high biodiversity in Anatolia for many years, it was thought to be represented by only a few species. A comprehensive study has recently been conducted by Freyhof et al. (2018c), who revised the genus Cobitis in the Middle East and recognised a total of thirty species, eight of them as new to Turkish inland waters. Cobitis levantina, reported by previous studies to be in the Orontes and Seyhan rivers, was identified as C. anabelae by Freyhof et al. (2018c). The distribution area of the C. levantina is restricted to the lower part of the Orontes in Syria and in the Litani River drainage in Lebanon (Krupp and Moubayed 1992).
Planiliza abu is distributed in the Euphrates and Tigris River basins. P. abu is recorded for the first time in the Ceyhan River. Also, Esox lucius is widespread in rivers of the Anatolia. It is first recorded from the Seyhan River.
The Lake Gölbaşı is located in a national park in Adıyaman province (eastern Anatolia). It is connected to two lakes, named Azaplı and İnekli. These lakes are connected to the Ceyhan River. They have been separated in the past and their connections might be relatively new (Freyhof et al. 2018c;Saç et al. 2019). Today, the water transfer to the Ceyhan Basin is provided by the Çataltepe-Kartalkaya Line (GAP -Gaziantep Emergen-cy Drinking Water Supply) from the Göksu River in the Euphrates drainage. The water obtained from the Göksu River is transmitted to the Lake Gölbaşı through the siphon, tunnel and canal system. Therefore, it is expected that some species in the Euphrates will be in the Lake Gölbaşı in the near future. Alburnus sellal is widespread in the Euphrates basin. This study cited a new record of A. sellal in the Lake Gölbaşı.
This study was designed to provide an inventory of freshwater fish in the Seyhan, Ceyhan and Orontes basins, and to eliminate certain taxonomic uncertainties. Also, it should highlight the need to create a protection area for endangered species and endemic fishes. For future research, fieldwork especially focusing on estuaries and dam lakes is suggested for a better understanding of the fish fauna of these river systems. Acknowledgments I am grateful to Jörg Freyhof (Berlin) for allowing me to use data of collections (FSJF) and for supporting me with the photos (JF) of some species as well as Müfit Özuluğ (İstanbul) for allowing me to use his photos of Squalius seyhanensis. I am also very grateful to Davut Turan (Rize) and Cüneyt Kaya (Rize) for their comments on an earlier version of the manuscript and Davut Turan, Cüneyt Kaya, Züleyha Akpınar (Rize) and Mehmet Kuyumcu (Rize) for help in the fieldwork. Thanks to Baran Yoğurtçoğlu (Ankara) for his comments on the genus of the Paraphanius and also Jonathan P. (England) and Utku Avcı (Turkey) for reading the manuscript and improving the language. I also thank two reviewers for useful comments.