26. Neogobius bathybius (Kessler, 1877) (Fig. 21), Deepwater Goby

Gobius bathybius, Kessler, 1877: 17, pl. 1 (fig. 3); type locality: Svinoi Island, south of Baku, Caspian Sea, Azerbaijan, depth 756 feet ; types: type material of Gobius bathybius appears to be missing from the collection of St Petersburg State University .

Etymology: Greek, bathus = deep, refers to capture of the holotype in deep waters.

Distribution and habitat: Present in all three areas of the Caspian Sea (Fig. 22A). No records appear to exist from the east coast of the Middle Caspian Sea. A relatively deep water species found under pleio-mesohaline conditions and known from depths to 75 m and may occur deeper (Pinchuk et al. 2004b). Does not enter rivers (Pinchuk et al. 2004b).

Remarks: Formerly in the genus Chasar Vasil’eva, 1996. Neilson & Stepien (2009) included Gobius bathybius in the genus Ponticola because they then lacked access to specimens of bathybius . Molecular data by Zarei et al. (2021) and by Tajbakhsh et al. (2022) have provided support for its reclassification in the genus Neogobius . DNA sequence data analysis by Tajbakhsk et al. (2022) indicated that there is a single population of N. bathybius across the Southern Caspian Sea.

Material examined: ZM-CBSU S063, 3, off Babolsar, & ZM-CBSU S064, 1, off Neka, Mazandaran Province, Iran ; ZM-CBSU A256 - A297, 36, off Kiashahr, Gilan Province, Iran .

IUCN: LC (Bogutskaya 2020l).