Alburnus derjugini

Common name. Georgian shemaya.

Diagnosis. Distinguished from other species of Alburnus in Marmara, Black Sea, and Aegean basins by: ○ 50–70+2–5 lateral line scales / ○ usually 8½ branched dorsal rays / ○ 12–17½ branched anal rays / ○ ventral keel between posterior pelvic base and anus present and well developed / ○ 18–35, usually 22–31, gill rakers / ○ anal origin ½–2½ scales behind dorsal base, below dorsal ray 7–8 in some individuals / ○ ventral keel exposed for 3–12 scales in front of anus / ○ a faint, dark-brown mid-lateral stripe. Size up to 400 mm SL, resident fish in rivers or streams usually much smaller.

Distribution. Marmara and Black Sea basin. In Turkish Aegean: Bakırçay, Güzelhisar, south to Gediz drainage.

Habitat. A wide range of streams and rivers with moderate fast-flowing water and gravel substrate.

Biology. Seem to be a resident species, no migratory populations known.

Conservation status. LC.

Remarks. Shemayas were divided into 17 species (A. attalus, A. battalgilae, A. carinatus, A. chalcoides, A. danubicus, A. derjugini, A. istanbulensis, A. leobergi, A. mandrensis, A. mento, A. mentoides, A. nicaeensis, A. sarmaticus, A. sava, A. schischkovi, A. vistonicus, A. volviticus) based on morphometric and meristic characters. Some species grow large, others remain very small, some are migratory or non-migratory and many are restricted to small areas. Subsequent molecular studies (COI) did not support this diversity. Molecular differences between fish from the Caspian, Black Sea, and Turkish Aegean basins are very small. In contrast, species inhabiting the Black Sea basin and the northern Aegean mostly share one haplotype, indicating a recent common evolutionary history. As more material from Türkiye became available, the proposed morphological differences could not be confirmed, especially as the number of gill rakers overlaps much more than originally described. Because of the large overlap in morphological characters and no difference in COI DNA sequences, we treat A. attalus, A. battalgilae, A. carinatus, A istanbulensis, and A. nicaeensis as synonyms of A. derjugini. It is recommended to revisit the European species also.

Further reading. Battalgil 1941 (description of Turkish species); Özuluğ & Freyhof 2007 (rediagnosis); Kottelat & Freyhof 2007 (distribution, biology, diversity Europe); Geiger et al. 2014 (phylogeny); Mangit & Yerli 2018 (phylogeny); Bayçelebi et al. 2021a (Aegean populations); Sarıahmetoğlu 2024 (Morphology of Turkish shemayas).