caspius, Leuciscus frisii Lönnberg [E.] 1900:16 [Bihang till Kongl. Svenska vetenskaps-akademiens handlingar. Stockholm v. 26, afd. 4 (no. 8); ref. 17561] Volga River delta, Russia. Holotype (unique): NRM. Described as a "race or subspecies." •Questionably in the synonymy of Rutilus frisii (Nordmann 1840) -- (Kottelat 1997:78 [ref. 22952]). •Synonym of Rutilus frisii (Nordmann 1840), but a valid subspecies as described -- (Bogutskaya 1997:178 [ref. 23566]). •Synonym of Rutilus frisii (Nordmann 1840) -- (Bogutskaya 1998:69 [ref. 23589], Fricke et al. 2007:46 [ref. 29533], Jouladeh-Roudbar et al. 2020:143 [ref. 37983]) Current status: Synonym of Rutilus frisii (Nordmann 1840). Leuciscidae: Leuciscinae. Habitat: freshwater, brackish.