Sevruga

The sevruga, or starry sturgeon (Acipenser stellatus), is a species of sturgeon in the family Acipenseridae, one of the oldest surviving fish lineages, dating back over 200 million years. It is native to the Caspian, Black, and Azov Sea basins, with a small population historically present in the Adriatic Sea. Like other sturgeons, it is anadromous, spending most of its life in brackish seas and migrating up large rivers such as the Volga, Danube, and Ural to spawn on gravel beds. The species is easily recognized by its long, thin, upturned snout — proportionally the longest of any sturgeon — and rows of sharp bony plates called scutes running along its body in place of scales. Decades of overexploitation, habitat loss, and river damming have caused severe population declines, and the sevruga is now classified as Critically Endangered.

Sevruga are elongated, spindle-shaped sturgeons with a distinctly long, narrow, upturned snout that makes up nearly 60% of the head length — the best field mark separating it from related Caspian sturgeons.

Key features:

• Five rows of bony scutes: 1 dorsal, 2 lateral, 2 ventral rows, star-shaped and sharply keeled
• Long, thin, blade-like snout that curves upward at the tip
• Grey to olive-brown back, pale silvery-white belly
• Barbels positioned closer to the mouth than the snout tip
• Typical adult length 1-1.5 m, exceptionally to 2.2 m
• Heterocercal (asymmetrical) tail fin typical of sturgeons

It differs from the similarly ranged Russian sturgeon (A. gueldenstaedtii) by its much longer, narrower snout and more numerous, sharper scutes, and from the ship sturgeon (A. nudiventris) by lacking a fully scaled belly.

Sevruga are anadromous, spending the majority of their adult lives foraging in the brackish waters of the Caspian, Black, and Azov Seas before migrating into connected river systems to spawn. Preferred marine habitat includes soft sediment areas of continental shelf zones at moderate depths, where they forage along the bottom. For reproduction, adults travel far upstream into major rivers such as the Volga, Ural, Kura, and Danube, seeking fast-flowing stretches with gravel or rocky substrate for egg deposition. Juveniles remain in fresh water for a period before migrating downstream to brackish nursery grounds. Dam construction across much of its historic river range has cut off access to traditional spawning grounds, restricting the species to a fraction of its former distribution.

Sevruga are solitary, bottom-oriented fish that forage using sensitive barbels and a protrusible, tube-like mouth to detect and suck up invertebrates and small fish buried in soft sediment. They have no teeth as adults and rely entirely on this vacuum-style feeding method. Spawning migrations begin in spring and can extend into summer, with mature adults undertaking long upstream journeys timed to river flow and temperature. Females release large numbers of adhesive eggs over gravel beds, which are fertilized externally; no parental care follows. Sevruga mature slowly, with males typically reaching reproductive age around 7-8 years and females later, contributing to their vulnerability to population decline. As bottom feeders, they play a role in reworking river and seabed sediments.