Sterletus huso (Linnaeus, 1758)

Freyhof, JÖrg, Yoğurtçuoğlu, Baran, Jouladeh-Roudbar, Arash & Kaya, Cüneyt, 2025, Handbook of Freshwater Fishes of West Asia, De Gruyter : 51-52

Sterletus huso

Common name. Beluga

Diagnosis. Distinguished from other species of Acipenser and Sterletus in West Asia by: ● gill membranes joined and free from isthmus / ● mouth very large, crescent-shaped / ● barbels laterally flattened / ○ 9–17 dorsal scutes / ○ 37–53 lateral scutes / ○ 7–14 ventral scutes / ○ 17–36 gill rakers. Largest documented size 8000 mm TL and 3200 kg, but generally below 5000 mm TL and 1000 kg.

Distribution. Caspian, Black, Marmara, Azov, and Adriatic Sea basins.Extirpated and actually reintroduced in Adriatic basin.

above 10°C. Larvae drift on currents; juveniles then move to shallower habitats before migrating to sea during their first summer. Remain at sea until maturity. Feeds on a wide variety of benthic molluscs, crustaceans and small fish.

Conservation status. CR; survival appears to depend only on stocking. Very rare in Black Sea basin. Almost all spawning grounds lost due to dam construction. Heavily overfished. Caspian populations are under massive pressure from overfishing and loss of spawning habitat. Almost all migrating spawners are poached below Volgograd dam.

Further reading. Vlasenko et al. 1989a (biology).

Habitat. At sea,pelagic,following food organisms. Migrates further upstream to spawn than any other sturgeon (in Danube to Germany). Spawns in strong-current habitats in main channel of large and deep rivers on rocky or gravelly bottoms. Juveniles spend first summer in shallow river habitats.

Biology. Anadromous. Males first spawn at 10–16 years, females at 14–20 years. Spawns every 3–4 years in April–June. A complicated pattern of spawning migrations includes a peak in late winter and spring and a peak in late summer and autumn. In spring, individuals migrate from sea prior to spawning. Individuals migrating in autumn remain in river until following spring. Yolk sac larvae pelagic for 7–8 days, drifting with current. Juveniles migrate to sea during their first summer and remain there until maturity. At sea, feeds on a wide variety of fish; seals and birds have also been reported as prey.

Conservation status. CR; survival appears to depend only on stocking. Extirpated from Adriatic (1970s) and Sea of Azov. Last populations in Black Sea basin migrate to Danube and Rioni ( Georgia). All other populations almost extirpated due to overfishing and damming of spawning rivers. Occasional individuals are still recorded from Azov and Black Seas. No natural spawning in Iranian or Turkish waters. Most females recorded are in their first year of maturity.

Further reading. Pirogovskii et al. 1989 (biology).

Sterletus huso sold illegally at a roadside market close to Batumi in Georgia in 2014. Sterletus nudiventris ; aquaculture, Iran; ~ 750 mm TL. © K. Abbasi.