Gobio caucasicus, Kamensky, 1901

Freyhof, JÖrg, Yoğurtçuoğlu, Baran, Jouladeh-Roudbar, Arash & Kaya, Cüneyt, 2025, Handbook of Freshwater Fishes of West Asia, De Gruyter : 254-255

Gobio caucasicus

Common name. Caucasian gudgeon.

Diagnosis. Distinguished from Gobio species in Caucasus by: ● pectoral reaching to or one scale in front of pelvic origin in mature male / ○ chest scaled between pectorals, scales extending forward beyond pectoral base (at least in some individuals of any population) / ○ head width at anterior eye-margin 9–10 % SL / ○ distance between pelvic origin and anal origin 3.3–4.1 times in distance between anus and anal origin / ○ head length 26–28 % SL / ○ head depth at nape 16–17 % SL, at eye 48–62 % HL / ○ head width 15–17 % SL, 58–62 % HL / ○ eye diameter 4–6 % SL, 3.1–3.7 times in head depth, 1.4–1.5 times in interorbital distance (at 50–60 mm SL) / ○ depth of caudal peduncle 33–36 % HL / ○ snout rounded, distinctly concave anterior to nostril. Size up to 100 mm SL.

Distribution. Russia: Caucasian Black Sea basin. In Kuma, Terek, and Sulak drainages in Caspian basin.

Habitat. Lowland and foothill streams and rivers, usually in slow to moderate-flowing waters on sandy or gravelly bottoms. Absent from high altitude streams with fast currents and low water temperatures.

Biology. No data.

Conservation status. LC.

Remarks. The gudgeons of the Caucasian Black Sea basin of Russia are usually identified as G. caucasicus . This species has been described based on syntypes from the European Caspian basin (often identified as G. holurus ) and syntypes from the Rioni in Georgian Black Sea basin (conspecific with G. artvinicus based on molecular data). Molecular data ( COI) show that some populations of “ G. caucasicus ” from the Black Sea basin are closely related to the Caspian G. holurus; others are closely related to G. kubanicus, G. brevicirris and G. krymensis from the European Black Sea basin. Finally, some populations represent a distinct molecular lineage, but the situation needs to be better understood. As different molecular lineages are found in sympatry, introgressive hybridisation is likely to have played a major role. This makes it difficult to classify species based on mtDNA alone. The identity of G. caucasicus still needs to be solved, as no lectotype has been identified. For now, we identify G. holurus as conspecific with G. caucasicus, as two of three syntype localities are within the range of this species.

Further reading. Berg 1949b (description); Kottelat & Freyhof 2007 (diagnosis as G. holurus ); Turan et al. 2016a (characters as G. cf. caucasicus ).

Gobio fahrettini ; Ilgın basin, Türkiye; ~ 90 mm SL.