Scardinius erythrophthalmus (Linnaeus, 1758)

Freyhof, JÖrg, Yoğurtçuoğlu, Baran, Jouladeh-Roudbar, Arash & Kaya, Cüneyt, 2025, Handbook of Freshwater Fishes of West Asia, De Gruyter : 398-399

Scardinius erythrophthalmus

Common name. Rudd.

Diagnosis. Distinguished from S. elmaliensis in West Asia by: ● 8−13 gill rakers / ● 9−13½, usually 10−12½, branched anal rays. Size up to 350 mm SL.

Distribution. In West Asia, in deltaic lakes and lower reaches of Inguri, Rioni, and Çoruh (Georgia), Marmara and Black Sea basins east to Sakarya. Also in lower Yeşilırmak and Kızılırmak ( Türkiye). Absent between Kızılırmak and Coruh, as well as between Sakarya and Kızılırmak. In Caspian basin, lower reaches of Kura and Aras and lakes in Lenkoran region ( Azerbaijan), Anzali and Boojagh wetlands, and Sefid drainage ( Iran). Most European rivers north of Pyrenees and Alps, eastward to Ural and Eya drainages, Aral and White Sea basins; Black Sea basin in Europe. Naturally absent from Iberian Peninsula, Adriatic basin, Italy, Greece south of Pinios drainage, Great Britain north of 54°N, Ireland, and Scandinavia north of 62°N. Introduced in northern Italy, Spain, and Corsica.

Habitat. Nutrient-rich, well-vegetated lowland rivers, backwaters, oxbows, ponds, and lakes. Spawns on roots or submerged vegetation.

Biology. Lives up to 17 years. First spawns at 3–4 years. Fractional spawner. Spawns April–July when water temperature is 12–22°C. Males congregate at spawning sites and drive mature females, often with much splashing,

Conservation status. VU; declining within its small range. Most populations appear to inhabit reservoirs. Extirpated from Lake Karataş.

Remarks. Molecular data place S. elmaliensis as a sister clade to S. erythrophthalmus .

Further reading. Bogutskaya 1997b (description); Geiger et al. 2014 (molecular data); Karataş et al. 2016 (molecular data, distribution).

into dense vegetation to spawn. Eggs are very sticky. Feeds mainly on plankton, terrestrial insects, and plant material. Able to adapt to adverse environmental conditions by slow growth and small size at maturity (stunted populations), e.g., in Anzali Lagoon, with a maximum total length of 146 mm, living up to 5 years and spawning at age 1+.

Conservation status. LC.

Further reading. Elanidze 1983 (distribution, biology, Georgia); Kottelat & Freyhof 2007 (distribution, biology); Uğurlu et al. 2008 (distribution in Türkiye); Patimar et al. 2010a (Anzali Lagoon).

Squalius species diversity of Squalius is still incompletely understood Chubs are medium-sized to large fishes that inhabit lakes, and future studies of nuclear DNA may change the species slow-flowing large rivers, and hill streams. In this genus, 38 diversity recognised here. In Anatolia, Eastern Greece, and species are recognised, 16 of which are found in West Asia. Bulgaria, one very widespread molecular group is distrib- They are particularly abundant in medium-sized streams uted, having the mtDNA of S. orpheus . However, nuclear and small rivers with gravel substrate and may constitute DNA data strongly suggest that Greek and Anatolian pop- a significant portion of the fish biomass in such habitats. ulations are two species: S. orpheus and S. cappadocicus . Squalius is characterised by scaled midventral keel in front Indeed, selected populations are quite different from each of the anus, a complete lateral line, a slightly subterminal other and there are plenty of intermediate populations, mouth, the dorsal origin behind the pelvic base, two rows making separating species impossible for now. An addiof pharyngeal teeth, the absence of a prominent grey or tional complex situation is found in the Persian Gulf basin, brown lateral stripe (a very indistinct stripe is present in a where S. lepidus , S. berak , and S. verepi often share the same few species), 7–10½ branched anal rays and 7–9½ branched mtDNA sequences. They seem also to have often hybridised dorsal rays. In Anatolia, mtDNA studies have only partially and such hybrids have locally stabilised, and populations corroborated the morphological species hypothesis in are being morphologically intermediate between S. berak /S. recent years. This is due to several factors, including intro- verepi and S. lepidus , challenging their identification. In gressive hybridisation and the possibility that some species other populations, the external appearance of the fish is may have arisen through genetic drift in small founder pop- identical to that of one species, yet the mitochondrial DNA ulations invading new habitats. Genetic drift is a potential (mtDNA) belongs to the different species. Genomic studies evolutionary pathway of S. carinus , which has a very small will shed some light on Squalius ’ evolutionary past, hoperange adjacent to its closely related sister species. Addition- fully soon. Further reading. Durand et al. 2000 (molecular ally, some species have been identified as synonyms due diversity); Özuluğ & Freyhof 2011 (morphological diversity to underestimating their morphological variability. The in Western Anatolia).

Keys to species of Squalius in West Asia

Contributing author: Esra Bayçelebi ( Rize) contributed to the chapter on the genus Squalius .

Black and Marmara Sea basins

1a - Vertical black bar behind opercle conspicuous; anal rays and membranes orange or red in life in adults larger than 150 mm SL. ……………… S. orientalis

1b - Vertical black bar behind opercle in-conspicuous; anal membranes whitish, yellowish, very pale-orange-grey or blackish, rays usually blackish in life in adults larger than 150 mm SL. ………………2

2a - 47–49 total lateral-line scales; head length 24–26 % SL. ……………… S. cii

2b - 40–46 total lateral-line scales; head length 25–29 % SL. ………………3

3a - Dorsal origin situated behind of pelvic base; posteriormost point of anal at tip of 7 th or 8 th branched ray. ……………… S. pursakensis

3b - Dorsal origin situated above pelvic base; posteriormost point of anal at tip of 3 rd –5 th branched ray ……………… S. cappadocicus

Central Anatolian endorheic basins, Aegean and Mediterranean basins east to Bay of Antalya

1a - 14–15 circumpeduncular scales; scale pockets on flank with a dark-grey, crescent-shaped mark. ………………2