Rutilus frisii

Freyhof, JÖrg, Yoğurtçuoğlu, Baran, Jouladeh-Roudbar, Arash & Kaya, Cüneyt, 2025, Handbook of Freshwater Fishes of West Asia, De Gruyter : 392-394

Rutilus frisii

Common name. Vyrezub.

Diagnosis. Distinguished from other species of Rutilus in West Asia by: ● body almost cylindrical / ● 53–64+3 lateral-line scales / ● abdomen posterior to pelvic rounded / ○ mouth subterminal / ○ iris and fins grey or slightly yellowish / ○ usually 9½ branched dorsal rays / ○ 9–10½ branched anal rays / ○ no midlateral stripe / ○ lateral line complete. Size up to 680 mm and 8 kg.

Distribution. Black and Azov Sea basins, rare in Danube (mostly restricted to few subalpine lakes), absent from Kuban; landlocked populations in reservoirs on Don; Caspian basin, common from Terek to Atrak drainages, very rare in northern Caspian basin (in Volga formerly as far as Perm and in Ural). Landlocked population in Anatolian Lake İznik.

Habitat. Coastal lakes connected to rivers, and lowland reaches of large rivers close to coast at sea. In estuaries, found in deep layers down to 20 m. Tolerates salinities up to 7–12 ‰. Inland populations inhabit large lakes or reservoirs. Semianadromous populations often enter in small rivers or streams with strong currents on gravel beds to spawn.

Biology. Riverine, lacustrine or semi-anadromous. Lives up to 12 years. Spawns first time at 4–5 years, with 430–500 mm SL. Enters rivers in second half of October (Black Sea, rarely in Caspian Sea). When rivers are ice-covered, spawning migration stops and resumes when ice breaks up or even under ice in February–April. Populations spawning in small streams enter in February–April. Spawns in April– May, somewhat earlier in southern drainages (February in Terek), when temperature reaches 8°C, peaking at 13–15°C.

Rutilus frisii ; Tajan, Iran; ~ 300 mm SL.

Eggs adhere to rocks and gravel, rarely to submerged vegetation. Adults return to estuary immediately after spawning to feed. Eggs hatch in 10–16 days at 12–19°C. Juveniles migrate to estuaries during first summer (August). Inland populations migrate from lakes, reservoirs, or middle reaches of rivers to tributaries or headwaters in spring. Larvae and early juveniles feed on zooplankton, algae, and insect larvae. Adults feed mainly on molluscs and Rhithropanopeus crabs, supplemented by other benthic invertebrates. Stops feeding during migration, spawning and overwintering.

Conservation status. LC: Lake İznik population declined in the late 20 th century and may now be extirpated. Migratory populations very rare in Black Sea basin. In Caspian, populations declined since 1980s and may continue to decline. Dams and large-scale overfishing have made natural spawning almost impossible in Caspian, and populations are maintained largely by massive stocking of 120–140 million juveniles annually in Iranian waters.

Rutilus lacustris ; Aras drainage, Armenia; ~ 250 mm SL. © B. Lewin.

Further reading. Berg 1949b (biology, morphology); Kazancheyev 1981 (Caspian; biology); Magomedov 1981 (biology); Movchan & Smirnov 1981 (Black Sea; biology); Belyaeva et al. 1989 (biology); Kotlík et al. 2008 (phylogeography).

Rutilus lacustris ; Kura, Azerbaijan; ~ 200 mm SL.