Taxonomic assessment and distribution of fishes in upper Kura and Aras river drainages

In the present study, the actual fish fauna of the upper Kura and Aras river drainages in Turkey were re-examined. The distribution and latest taxonomic status of the species were assessed. The study area comprises the upper part of Kura and Aras river drainages, in Turkey. Overall, 32 sampling sites were prospected between 2004–2018 to inventory fish species in the area and a total of 33 species were recognized, five of which are recorded for the first time from the Turkish part of upper Aras river drainage, namely Alburnus hohenackeri, Blicca bjoerkna, Gobio artvinicus, Neogobius fluviatilis and Rhodeus amarus.


Introduction
The Kura and Aras rivers and their tributaries are located in the south of the Caucasus Mountains. Both rivers originate in Anatolia and flow towards the east. Kura, after leaving the borders of Turkey, passes through Georgia, and then flows into Azerbaijan. Aras, before leaving Turkey, flows along the borders between Turkey and Armenia, between Turkey and Nakhchivan and then flows throughout the borders between Iran and three countries (Nakhchivan, Armenia and Azerbaijan, respectively). Both rivers further merge in Sabirabad (Azerbaijan) and flow into the Caspian Sea. Fricke et al. (2007) recorded many fish species new to Turkish freshwaters. Most of these records were given from some of the transboundary rivers (e.g. Maritza, Orontes, Tigris-Euphrates and Kura-Aras river systems, and Çoruh River). These records were partially accepted and followed as most of these new occurrences were not ascertained through specimens deposited in a national collection. This situation has caused an overestimate of the number of freshwater fish species in Turkey (Çiçek et al. 2015, 2018). Çiçek and Sungur Birecikligil (2016) listed fish species of the upper Kura-Aras River drainages based on their own observations and earlier records in the literature. They observed 19 species but listed 32 species by including 13 species that were recorded in the previous studies.
Inconsistent and erroneous occurrence records of species given by previous studies from upper Kura and Aras drainages have resulted in contradictory taxonomic evaluations among researchers. Therefore, here we attempt to re-assess the fish fauna of the upper Kura and Aras river drainages based on materials from our field surveys and up-to-date taxonomic nomenclature.

Study area
The study area comprises the upper part of Kura and Aras river drainages, the Caspian Sea basin. Overall, 32 sampling sites, 9 from Kura and 23 from Aras drainages, were detected to reveal fishes in the area (Table 1). We followed Berg (1949) and Kottelat and Freyhof (2007) to identify species, Van der Laan et al. (2015) to arrange species in families. All species were arranged alphabetically within their own families.

IUCN status.
Least concern (LC). Table 2. List of the species to be excluded from the checklist of Kura-Aras drainages in Turkey.

Species
Explanation 1 Abramis brama (Linnaeus, 1758) The species reported in the Turkish Kura and Aras drainages by Fricke et al. (2007). Actually, the species is distributed in the Caspian Sea and it is possible to occur in Turkey. However, it was not found by Çiçek and Sungur Birecikligil (2016), as well as in our surveys in the area. Therefore, it was omitted from the fishes of upper Kura and Aras drainages until the species has been documented by the observed material. 2 Acipenser persicus Borodin, 1897 The species was erroneously reported in the upper Aras drainages by Fricke et al. (2007), followed by Çiçek et al. (2015) and Çiçek and Sungur Birecikligil (2016). The species has not been documented by the observed material. 3 Alburnus chalcoides (Güldenstädt, 1772) Because of the problematic taxonomy of the genus (Bogutskaya et al. 2017), the species was recorded in the Black Sea and the Caspian Sea basin in Turkey by many researchers (e.g. Turan 2003;Geldiay and Balık 2007;Fricke et al. 2007;Çiçek et al. 2015). However, the occurrence of the third shemaya, except A. filippii and A. hohenackeri, has never been documented by the observed material. 4 Alosa caspia (Eichwald, 1838) This predominantly marine and estuarine species has never been observed in any parts of the Turkish Kura and Aras drainages, except erroneously in a report by Fricke et al. (2007), followed by Çiçek et al. (2015) and Çiçek and Sungur Birecikligil (2016). 5 Alosa braschnikowi (Borodin, 1904) The species was recorded in Turkish Aras drainages as Rutilus sojuchbulagi (Fricke et al. 2007). However, it is a brackish species and nonanadrom (Afraei Bandpei et al. 2012). Therefore, the occurrence of the species in the Turkish Aras River is not deemed likely. 6 Caspiomyzon wagneri (Kessler, 1870) It is an endemic lamprey to the Caspian Sea basin and may be extinct from Kura (Berg 1949). It was claimed that the species was extinct in Turkey (Fricke et al. 2007;Çiçek and Sungur Birecikligil 2016). However, the species has never been reported in Turkey. 7 Chelon saliens (Risso, 1810) The species has never been reported in the upper Kura and Aras drainages until an erroneous record by Fricke et al. (2007). The record was not supported by the following researchers (Çiçek et al. 2015;Çiçek and Sungur Birecikligil 2016). 8 Gambusia holbrooki Girard, 1859 Erroneously reported to be in the upper Aras drainages based on the following literature " Kuru 2004, Fricke et al. 2007Çiçek et al. 2015". However, none of these studies had directly reported this species in the area. 9 Luciobarbus caspius Berg, 1914 The species erroneously reported in the upper Aras drainage by Fricke et al. (2007), followed by Çiçek et al. (2015) and Çiçek and Sungur Birecikligil (2016). The species has not been documented by the observed material. 10 Luciobarbus brachycephalus (Kessler, 1872) Fricke et al. (2007 verified the presence of the species from Hasankale Stream (Erzurum Province) based on museum material. However, this claim has not been supported by the following researchers (Çiçek et al. 2015;Çiçek and Sungur Birecikligil 2016). The species reported from the lower Aras river (Coad 2020). Even though we have a sampling site close to Hasankale, we did not observe the species in the area. Moreover, a third Luciobarbus species, except L. capito and L. mursa, was not found in the upper Aras drainages. Perhaps, the museum material presented by Fricke et al. (2007) was mislabelled or misidentified. We omitted it from the fishes of upper Kura and Aras drainages until the species has been documented by the observed material. 11 Neogobius melanostomus (Pallas, 1814) These three gobiid species had never been reported in the upper Kura and Aras drainages until they were erroneously recorded by Fricke et al. (2007). These records were not supported by the following researchers (Çiçek et al. 2015; Çiçek and Sungur Birecikligil 2016). We omitted them from the fishes of upper Kura and Aras drainages until the species have been documented by the observed material. 12 Neogobius syrman (Pallas, 1814) 13 Ponticola ratan (Pallas, 1814) 14 Proterorhinus marmoratus (Pallas, 1814) The species reported from lower reaches of Aras, near Baku (Kessler 1877;Derzhavin 1934;Berg 1949). Erroneously reported in the upper Aras drainages by Fricke et al. (2007). They also claimed the species was extinct in the Caspian Sea watersheds. 15 Romanogobio persus (Günther, 1899) The type locality of this species from Gader Chai, Lake Urmia basin. The specimens collected from Horasan (Erzurum) were identified as R. persus (Kuru, 1975). This record was followed by Kuru (2004) and, Fricke et al. (2007). However, Çiçek et al. (2015) and Çiçek and Sungur Birecikligil (2016), claimed that maybe the species was misidentified. We omitted the species from the fishes of upper Kura and Aras drainages for now. See remarks of R. macropterus for details about the taxonomy of Romanogobio populations in the area. 16 Rutilus kutum (Kamensky, 1901) The species recorded from Turkey as Rutilus frisii caspius Kuru (2004), later synonymised with R. kutum (Bogutskaya and Iliadou 2006). This record was followed by Fricke et al. (2007). However, the occurrence of the species has never been documented by the observed material. Recently, Kuljanishvili et al. (2020) treated R. kutum as a junior synonym of R. frisii. 17 Sabanejewia caspia (Eichwald, 1838) The species reported in the upper Kura and Aras drainages by Fricke et al. (2007), probably instead of S. aurata which had already been known in the area. This report followed by Çiçek et al. (2015) and Çiçek and Sungur Birecikligil (2016). The species is distributed in the southern Caspian Sea basin (Anzali wetland, Sefid River and Amirkolayeh Wetland) (Sayyadzadeh et al. 2018) 18 Sander lucioperca (Linnaeus, 1758) It was reported that the species spawned in the lower and middle Kura River (Berg 1949). Çiçek and Sungur Birecikligil (2016) erroneously reported it in the upper Aras drainages based on the following literature " Kuru 2004, Fricke et al. 2007Çiçek et al. 2015". However, none of these studies had reported this species in the area. 19 Squalius orientalis Heckel, 1847 The species was erroneously reported in the upper Aras drainages by Çiçek et al. (2015) and Çiçek and Sungur Birecikligil (2016).
The type locality of the species is Abkhazia, Black Sea basin. S. turcicus and S. agdamicus are inhabiting Kura and Aras drainages (Bayçelebi 2019). 20 Stenodus leucichthys Abdurakhmanov, 1950 The species was erroneously reported to be in the upper Aras drainage by Fricke et al. (2007), followed by Çiçek et al. (2015) and Çiçek and Sungur Birecikligil (2016). Poursaeid and Falahatkar (2012) discussed the distribution of the species in the Caspian Sea basin, however, they did not mention the occurrence of the species in the upper Kura and Aras rivers. Distribution in the area. The species was found in Lake Çıldır and streams Gaziler and Yalnızçam. It was also reported from Lake Aktaş and Stream Sarısu (Çiçek and Sungur Birecikligil 2016). Common / local names. Distribution in the area. The species was found in stream Gaziler, B-20 canal and Lake Çıldır.

Cyprinus carpio Linnaeus, 1758
Note. Both native and introduced Cyprinus carpio inhabit Lake Çıldır. The native common carp is very distinct due to its slenderer body and yellow general body color (Fig.  3b). When compared to the introduced one, the native C. caripo is very popular and economically valuable among the local people in the area.
Distribution in the area. The species was found only in stream Gaziler.

IUCN status.
Least concern (LC).  Distribution in the area. The species is recorded in B-20 canal located very close to the border with Armenia. Rhodeus amarus was recorded from Lake Urmia and Caspian Sea basins in Iran (Derzhavin 1934;Holčík and Oláh 1992;Kiabi et al. 1999;Abbasi et al. 1999;Abdoli, 2000;Ghasemi et al. 2015;Coad 2018). Probably it also occurs in Aras River in Armenia (Pipoyan, 1996 Distribution in the area. The species has been known to occur in Çoruh River and has not been recorded in any another place, including Kura and Aras river drainages, despite intensive field work. However, it has recently been declared that G. artvinicus translocated to the Caspian Sea basin and occurs in Armenia, Azerbaijan and Georgia (Kuljanishvili et al. 2020). In the present study also, some specimens belonging to genus Gobio were observed and they are superficially similar to G. artvinicus.
Distribution in the area. The species was recorded only from Lake Aktaş. It was also recorded in Lake Çıldır (Çiçek and Sungur Birecikligil 2016).

IUCN status.
Least concern (LC). Distribution in the area. Kura and Aras River drainages in northeastern Turkey.

Remarks.
The type locality of the species is the Caucasus. The Kura population was identified as R. macropterus. However, we observed some morphological differences between Kura and Aras populations obtained in this study.
The Aras population has a slenderer body and caudal peduncle than R. macropterus from Kura (Fig. 4d, 4e). Therefore, we encourage detailed morphologic and molecular research including the Kura, Aras and Urmia populations to clarify the taxonomic position of the Aras population.

IUCN status.
Least concern (LC).    Note. The occurrence of the species in the region has been reported by earlier studies based on estimates (Fricke et al. 2007;Çiçek et al. 2015). A. hohenackeri was documented with the materials observed for the first time in the B-20 canal, Turkey. We observed two syntopic shemeya from the B-20 canal. Alburnus hohenackeri is easily distinguished from A. flippii by having a stout and deep body as well as large scales (Fig. 6b, c).

IUCN status.
Least concern (LC). Distribution in the area. The species is widespread in Kura and Aras river drainages.

IUCN status.
Least concern (LC).  (ICZN 1999), it is clearly indicated that: "A species-group name, if a noun in the genitive case (see Article 11.9.1.3) formed directly from a modern personal name, is to be formed by adding to the stem of that name -i if the personal name is that of a man, -orum if of men or of man (men) and woman (women) together, -ae if of a woman, and -arum if of women; the stem of such a name is determined by the action of the original author when forming the genitive." Therefore, the name of the species is treated here as Oxynoemacheilus veyselorum.

IUCN status.
Least concern (LC).  Dorofeyeva (1967) and the figure and description of Kottelat & Freyhof (2007). Therefore, we consider that species closely related to S. ciscaucasicus, and we encourage further research to clarify the trout taxonomy in the area.
Distribution in the area. The species native for the Caspian Sea basin (Pinchuk et al. 2003). The species was recorded from B-20 canal. It is the first record for the Turkish Aras River.

IUCN status.
Least concern (LC). not included endemic fish species of Turkey by Çiçek et al. (2018). However, the species has never been reported from Armenia or adjacent countries. Even though these species are restricted to the Turkish part of Kura River, the population density detected was high. Probably, this was due to the limited human population in nearby rural areas, hence the negative effect of anthropogenic pollutants. In addition, hydro power plants could not be installed in the area since the geographical structure of the region is a flat plateau. Both species are already assessed as "Least concern" by IUCN.

Discussion
Alburnus hohenackeri, Blicca bjoerkna, Gobio artvinicus, Neogobius fluviatilis and Rhodeus amarus were recorded for the first time in the upper reaches of Aras River in Turkey by the observed samples. Turan et al. (2012Turan et al. ( , 2014aTuran et al. ( , 2014bTuran et al. ( , 2017Turan et al. ( , 2020 showed that there is a high diversity within Salmonids in Anatolia. The presence of five trout species in Turkish Mediterranean tributaries and four species in Euphrates River drainages encouraged us to compare the trout population of Kura-Aras River systems in detail. Also based on a limited number of specimens, our study evidenced that Kura populations belong to Salmo caspius, but populations from Aras drainage need further study. We are considering the occurrence of S. ciscaucasicus and an unnamed trout species in upper Aras drainages. Therefore, we encourage a detailed study on trout taxonomy in the upper Aras drainages. Introduced salmonid, Coregenus albula, was recorded in Lake Aktaş, which is a transboundary lake shared between Turkey and Georgia (Yerli 2019). During our single survey in July 2017 in the Lake Aktaş, we were not able to find this species. Perhaps this species was introduced to the lake after the present survey.
There are two species categorized under the red list of IUCN; both were assessed as Vulnerable. The first is native populations of Cyprinus carpio, which were observed only in Lake Çıldır in the area. The population density of the species is declining due to overfishing and destruction of breeding and feeding areas (Zengin et al. 2012). Besides, invasive Pseudorasbora parva and Carassius gibelio, and introduced Cyprinus carpio inhabit Lake Çıldır and compete with the native C. carpio populations for food and habitat. The second species is Luciobarbus capito, which was found only in stream Gaziler in the present study. However, Çiçek and Sungur Birecikligil (2016) recorded the species in five sampling sites. We observed only 4 samples in stream Gaziler despite our intense efforts. This suggests that L. capito population is drastically declining due to damming in the 1950's and 1960's in the Caspian Sea. L. capito decline is continuing, especially for mature individuals (Freyhof and Kottelat 2008). Because of its big size, overfishing is also a major threat for L. capito.
There are nine species not evaluated against IUCN criteria. Among these: Capoeta kaput, C. saniae and Oxynoemacheilus veyselorum, were described after 2017; therefore they have not yet been assessed by IUCN. C. kaput was found only from B-20 canal in this study, and from two localities by (Levin et al. 2019). C. saniae was described from two localities by Eagderi et al. (2017), which were covered by the present study and resulted in the capture of only a few specimens. O. veyselorum was described from a single locality by Çiçek (2018), however, in this study, it was recorded from eight additional sampling sites, with multiple individuals. The situation with respect to C. kaput and C. saniae, in particular, would appear to be critical. Therefore, we encourage researchers to study the conservation status of these species.