Sterletus stellatus (Pallas, 1771)

Sterletus stellatus View Figure

Common name. Stellate sturgeon

Diagnosis. Distinguished from other species of Acipenser and Sterletus in West Asia by: ● snout very long (59–65 % HL), narrow, dorsoventrally compressed / ○ star-shaped bony denticles between rows of scutes / ○ no plate along posterior part of anal base / ○ 0–1 plate along lower edge of caudal peduncle / ○ 9–16 dorsal scutes / ○ 26–43 lateral scutes / ○ 9–14 ventral scutes / ○ base of barbels closer to mouth than to tip of snout / ○ lower lip interrupted in middle / ○ 24–29 gill rakers / ○ diploid. Size up to 2180 mm TL and 54 kg.

Distribution View Figure . Caspian, Black, Azov, and Aegean basins, ascending rivers to spawn. Introduced in Aral basin.

Habitat. At sea, in coastal and estuarine areas. Feed on bottom, usually on clayey sand, and intensively in middle and upper water layers. Spawns in strong currents in main channel of large and deep rivers, on stone or gravel bottoms. Also, spawns on flooded riverbanks; if gravel bottom is unavailable spawns on sand or sandy clay. Juveniles occupy shallow river habitats during first summer.

Biology. Anadromous. Males first spawn at 6–12 years, females at 8–14 years. Females spawn every 3–4 years and males every 2–3 years in April–September. Spawns only under relatively constant hydrological conditions. Fluctuating hydrological conditions result in high egg mortality. Upstream migration with two peaks in spring and autumn. Migrates at higher temperatures and therefore later than other sturgeons. Males spend no more than 6 weeks at spawning sites, and females only 10–12 days. Spent individuals return directly to sea. Yolk sac larvae pelagic for 2–3 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 crustaceans, molluscs and benthic and pelagic fish.

Conservation status. CR; survival appears to depend on stocking. Extirpated from Aegean Sea. In Black Sea basin, last natural populations still migrate to Danube and Rioni ( Georgia), where it is heavily overfished. Very few spawners remain in rest of Black Sea basin. Large numbers were stocked from Caspian to Azov basins in 1961–1986. Caspian populations under massive pressure from overfishing and loss of spawning grounds. Stocks are rapidly declining. Almost all migrating spawners poached below Volgograd dam.

Further reading. Shubina et al. 1989 (biology); Economidis et al. 2000 ( Aegean Sea).