Chondrostoma nasus (Linnaeus, 1758)

Freyhof, JÖrg, Yoğurtçuoğlu, Baran, Jouladeh-Roudbar, Arash & Kaya, Cüneyt, 2025, Handbook of Freshwater Fishes of West Asia, De Gruyter : 338-339

Chondrostoma nasus

Common name. Nase.

Diagnosis. Distinguished from other species of Chondrostoma in Aegean, Marmara, and Black Sea basins by: ○ 8–10½, usually 8½, branched dorsal rays / ○ usually 9, rarely 8 branched pelvic rays / ○ 52–72 (usually 60–63) total lateral line scales / ○ 24–31 gill rakers / ○ (9)10–11½ branched anal rays. Size up to 460 mm SL.

Distribution. Türkiye: Susurluk and Hoşap drainages on Biga peninsula. Danube, Dniestr, South Bug, and Dniepr drainages in Black Sea basin, Neman, Odra, and Vistula in southern Baltic basin and rivers of southern North Seas (westward to Meuse). Invasive or introduced in Rhône, Loire, Hérault, Seine ( France), and Soca ( Italy, Slovenia) drainages.

Habitat. Moderately to rapidly-flowing large to medium-sized rivers with rocky or gravelly bottoms. Spawns in fast-flowing waters on shallow gravel beds, often in small

Further reading. Elvira 1987 (description); Özcan & Balık 2011 (age and growth); İlhan et al. 2011 (growth, reproductive biology; as C. nasus ); Güçlü et al. 2013 (distribution); Güçlü et al. 2018 (morphology); Çiftçi et al. 2020 (phylogeny). tributaries. May show a strong size-dependent longitudinal distribution in smaller rivers, with adults occupying more upper reaches.

Biology. Lives up to 12 years. First spawns at 4–5 years. May migrate tens of kilometers to spawning grounds, often in tributaries, but does not occupy these in summer. Spawns March–May when temperature reaches 12°C. Males form large aggregations, with each male defending a small territory. Females spawn only once a year and, in some populations, for a very short time (3–5 days). Females lay sticky eggs burrowed in gravel. Feeding larvae live on banks below water surface. Early juveniles are benthic and inhabit very shallow shoreline habitats. As they grow, they leave banks for faster-flowing water. Recruitment closely linked to high spring temperatures, absence of spring floods and availability of shallow-water riparian habitats. Juveniles overwinter in backwaters or in celvics along banks. Adults form dense schools in lower reaches of rivers during winter. Larvae and early juveniles with superior and later terminal mouths feed on small invertebrates. Larger juveniles and adults with inferior mouths feed on benthic diatoms, and detritus scraped from hard substrate in habitats with strong currents.

Conservation status. LC.

Remarks. Populations in Adriatic basin from Aoos ( Greece, Albania) north to Drin and Skadar Lake basin constitute a separate valid species: C. ohridanum .

Further reading. Elvira 1987 (systematics); Nelva 1989 (biology); Maier et al. 1995 (biology); Kottelat & Freyhof 2007 (biology, distribution); Çiftçi et al. 2020 (phylogeny Susurluk population).

Chondrostoma regium ; upper Tigris, Türkiye; ~ 140 mm SL.

Chondrostoma regium ; Kor drainage, Iran; 124 mm SL.