Squalius orientalis, Heckel, 1847

Freyhof, JÖrg, Yoğurtçuoğlu, Baran, Jouladeh-Roudbar, Arash & Kaya, Cüneyt, 2025, Handbook of Freshwater Fishes of West Asia, De Gruyter : 415

Squalius orientalis

Common name. Georgian chub.

Diagnosis. Distinguished from other species of Squalius in Black Sea basin by: ○ 9½, rarely 8½ branched anal rays / ○ anal orange to red / ○ conspicuous vertical black bar behind opercle / ○ 41–46+1–2 lateral-line scales / ○ 10–12 gill rakers / ○ caudal peduncle depth 11–12 % SL / ○ posteriormost point at tip of 3 rd anal branched ray. Size up to 600 mm SL.

Distribution. Eastern Black Sea basin from Doğankent east to Çoruh and north to Ashe drainage and other small rivers south of Caucasus.

Habitat. Usually in small rivers and large streams with riffles and pools, even in very small mountain streams. On banks of slow-flowing lowland rivers and lakes, making spawning migrations to inflowing streams. Spawns in fast-flowing water over gravel banks.

Biology. Lives up to 16 years, females longer than males. Males first spawn at 2–3 years, females at 4–6 years. Juveniles gregarious, adults more solitary. Feeds on a wide variety of aquatic and terrestrial animal and plant material. Often forms hybrids with Alburnus .

Conservation status. LC.

Remarks. Molecular data suggest that this species is very closely related to S. turcicus from Aras, and both may be conspecific. However, S. turcicus usually has dark grey fins, whereas S. orientalis has orange fins, and S. turcicus lacks the prominent vertical black bar behind the opercle. We recognise S. cephalus and S. orientalis as two species based on molecular characters alone, as their morphology has yet to be studied. Molecular data suggest that S. orientalis might have a much wider distribution in the northern Black Sea

basin, including all rivers east of Danube and tributaries of Baltic Sea west to Odra and eastern tributaries of Elbe ( Czech Republic and Germany). Within this population group, S. wjatkensis from the Azov and northern Caspian Sea basins (Volga) and S. latifrons may be considered additional valid species in future. Squalius latifrons is an available name for chubs closely related to S. orientalis from southern Finland, Sweden (north to around Stockholm), the Baltic basin, and tributaries of the northern and western Black Sea. Fish from Bulgarian coastal rivers in Black Sea basin also belong to this molecular group, and we suspect that they are identical to those identified as S. cephalus in northwestern Anatolia. Squalius cephalus is restricted to France, Great Britain, the Danube drainage, and the North Sea basin tributaries east of Elbe.

Further reading. Bayçelebi 2019 (description); Dedeoğlu et al. 2020 (biology); Coad 2021a (biology, morphology).

Squalius pursakensis ; Porsuk subdrainage in Sakarya drainage, Türkiye; ~ 160 mm SL.