Rutilus lacustris (Pallas, 1814)

Rutilus lacustris View in CoL View Figure

Common name. Taran.

Diagnosis. Distinguished from other species of Rutilus in West Asia by: ○ 39–42+2–3 lateral-line scales / ○ body laterally compressed / ○ abdomen posterior to pelvic compressed / ○ usually 10½ branched dorsal rays / ○ usually 9–10½ branched anal rays / ○ iris whitish to yellowish / ○ pectoral, pelvic and anal hyaline, yellowish to dark-grey / ○ lateral line complete / ○ no midlateral stripe / ○ 7–9 scales between dorsal origin and lateral line. Size up to 430 mm SL.

Distribution View Figure . Freshened areas of Caspian basin entering all tributaries. Eastern Black and Azov Seas, entering Don, Kuban, Dniepr, Dniestr, and rarely Danube drainages and lower parts of these rivers. Hari drainage (not native) but possibly native to Morghab ( Turkmenistan). Also, in Aegean basin (Struma and Maritza drainages and Lake Volvi). Widespread in Aral basin and Siberia from Ob east to Lena.

Habitat. Resident populations inhabit many lowland habitats, such as rivers, lakes, reservoirs, and canals. Migratory fish spend most of the year in shallow, brackish coastal waters. At sea, adults are most abundant at depths of 2.5–4.0 m and 2–4 ‰ in summer. Enters freshwaters of estuaries, lagoons, and lower reaches of rivers to spawn.

Biology. Resident and semi-anadromous populations. Usually mature at 2–4 years and live 10–15 years. Comes to coasts in August and enters rivers in September, peaking in October. Stops migrating at end of November and overwinters in main river or estuary. Spawning migration resumes with ice break-up in March (Dniepr). Spawns in April–May. Adults return to estuaries to feed immediately after spawning. Juveniles migrate to estuaries during first summer (August). Resident populations may undertake considerable river migrations, usually spawning in flooded meadows and backwaters. Lacustrine populations usually spawn in inflowing rivers or on lake shores. Spawning usually occurs at temperatures above 10–12°C, usually on submerged vegetation, but all types of substrates will be used if no vegetation is available. Several males typically follow a single female during spawning. Feeds on various plants, detritus, and invertebrates, locally molluscs or plankton dominate diet.

Conservation status. LC.

Remarks. Molecular data suggest that all Caspian populations (and many in Europe) belong to this species. Rutilus lacustris , described from Siberia, has long been considered a synonym of R. rutilus . It had already been accepted in Europe as a valid species under R. heckelii (Black Sea basin) and R. caspicus (Caspian basin). Molecular data support the view that both are conspecific and that populations occurring east to Lena and Lake Baikal all belong to R. lacustris . The situation is more complicated in the Black Sea and the northern Caspian basins, as there appears to be some introgressive hybridisation between R. rutilus and R. lacustris , and many hybrid populations occur in that region.

Further reading. Berg 1949b (biology, systematics); Holčík & Skorepa 1971 (biology); Kottelat 1997 (systematics); Kottelat & Freyhof 2007 (distribution, biology as R. heckeli & R. caspicus ); Larmuseau et al. 2009 (distribution); Geiger et al. 2014 (molecular data); Artaev et al. 2021 (distribution, hybrids with R. rutilus ).