Acipenser sturio, Linnaeus, 1758

Freyhof, JÖrg, Yoğurtçuoğlu, Baran, Jouladeh-Roudbar, Arash & Kaya, Cüneyt, 2025, Handbook of Freshwater Fishes of West Asia, De Gruyter : 49

Acipenser sturio

Common name. Atlantic sturgeon

Diagnosis. Distinguished from species of Sterletus in West Asia by: ○ many rhombic or elongated denticles between dorsal and lateral scutes / ○ a series of plates along posterior part of anal base / ○ 2–4 plates along lower edge of caudal peduncle / ○ first dorsal scute fused with head / ○ 24–40 lateral scutes / ○ base of barbels midway between mouth and tip of snout or closer to mouth / ○ barbels not fimbriate / ○ 15–29 gill rakers / ○ lower lip interrupted in middle / ○ diploid. Largest documented size 6000 mm TL and 1000 kg, but today rarely exceeds 2000 mm TL.

Distribution. Only spawning river in West Asia was Rioni ( Georgia). Found along all coasts of Mediterranean and Black Sea. Also, North and White Seas, and European coasts of Atlantic. Occasionally recorded from Iceland. Anadromous, in most large rivers, but not recorded from Danube upstream of delta. Currently confined to Garonne ( France).

Habitat. At sea, coastal and estuarine areas on soft ground. In freshwaters, estuaries, and large rivers.

Biology. Anadromous. Males first spawn at 9–13 years, females at 11–18 years. Females spawn every other year and males every year in March–August when temperatures rise above 20°C, later in northern populations and in populations spawning further upstream. Spawning migrations peak in spring, with a secondary weak peak in late summer and autumn. Individuals migrating in late summer overwinter in rivers and spawn in spring. Spawns in strong-current habitats, in large and deep rivers, on stone to gravel bottoms. Spent individuals return directly to sea. Some juveniles migrate to sea during first summer,but most leave freshwater habitats after 2–4 years and remain at sea until

maturity. At sea, feeds on a variety of molluscs, worms, crustaceans, and small fish. Atlantic populations feed benthically, while Black Sea populations feed in pelagic zone, mainly on anchovies.

Conservation status. CR; survival appears to depend only on stocking. Decline began in 19 th century or possibly earlier due to massive overfishing, damming, river regulation and pollution. Last natural spawning in 1994. Last remaining population (in France) still declining.Population in Rioni ( Georgia) disappeared in late 20 th century. Bycatch and accidental kills are still a major problem in France. Reintroduction programmes are underway in France and Germany.

Further reading. Holčík et al. 1989b (biology); Holčík 2000 (conservation); Elvira 2000 (biology); Bacalbasa-Dobrovici & Holčík 2000 (Black Sea population); Rochard, in Keith & Allardi 2001 (status in France); Ludwig et al. 2002 (genetics).