Oxynoemacheilus bergi Common name. Agstafa loach. Diagnosis. Distinguished from other species of Oxynoemacheilus in Caspian basin by: ○ caudal moderately deeply emarginate / ○ caudal–peduncle depth two times in its length. Size up to 71 mm SL. Distribution. Azerbaijan: Agstafa, a tributary of Kura. Habitat. No data. Biology. No data. Conservation status. DD; due to the very poor knowledge of this species. Remarks. This species might be conspecific with O. bergianus. Further reading. Çiçek et al. 2018 (rediscovery); Freyhof et al. 2021b (discussion). Oxynoemacheilus bergi and other names of Caspian loaches. It is challenging to ascertain the number of valid species and their correct names. This often necessitates travel to type localities in remote areas. One such case is explained here. Nemacheilus bergi was described from the Kura drainage in Azerbaijan and was treated as a valid species without examining fish from the type locality or any other justification. In the same study, N. alasanicus from the upper Alazani in the Georgian Kura drainage was treated as a synonym of N. bergi, again without examining any materials or arguments. Early authors clearly distinguished N. bergi from Oxynoemacheilus brandtii. The account of O. bergi does not correspond to O. cyri, another species known from the Kura. Oxynoemacheilus bergi could be a third species of Oxynoemacheilus in the Kura, which has yet to be found (again). The account on O. bergi does not correspond to O. veyselorum, which has only been found in the adjacent Aras. However, it cannot be ruled out that O. bergi might be conspecific with the species identified as O. bergianus, also found in the Aras drainage. Nevertheless, there are no records of O. bergianus from the Kura, and fieldwork in late 2024 aimed to resolve the issue but failed to find it. If O. bergianus were conspecific with O. bergi, it would become a junior synonym of O. bergi. It was also suggested that two other loaches occur in the Alazani, a tributary of the Kura: N. angorae alasanicus and N. brandtii gibbusnazus. Indeed, only O. brandtii, very common in the Kura, has been recently found in the Alazani. Nemacheilus angorae alasanicus might be conspecific with O. bergianus, and both could be conspecific with O. bergi. These species should be re-examined based on materials from their type localities, and considerable efforts should be made to find the mysterious Oxynoemacheilus bergi and O. alasanicus. This is a complex issue, demonstrating that even with the publishing of this book, many questions need to be resolved. Further reading. Berg 1898, Gratzianov 1907 (O. bergi); Elanidze 1983 (Alazani loaches).

Published as part of Freyhof, Jörg, Yoğurtçuoğlu, Baran, Jouladeh-Roudbar, Arash & Kaya, Cüneyt, 2025, Handbook of Freshwater Fishes of West Asia, GmbH, Berlin / Boston :De Gruyter on page 490, DOI: 10.1515/9783111677811, http://zenodo.org/record/17881367