Habitat and Ecology
At sea, at depths of up to 25 m. In rivers, in deep stretches with gravel or stone bottom. Spawns in fast-flowing water at sites with hard bottom, 1-2 m deep.
Semi-anadromous and riverine populations. Spawns for the first time at about 500-700 mm SL, 5-7 years, females later than males. Spawns in April-August, with peak at 23-27°C. Some individuals start spawning migration in late summer-autumn and spawn following spring after overwintering in river. Some enter rivers in early spring and spawn same year. Female lays 100,000-1,250,000 bright yellow eggs; in 2-3 portions during a single season. Eggs are semipelagic and hatch while drifting downstream after at least 2 days at 25°C. Larvae settle into places with slow current for 2-12 months, then drift downstream to sea (or reservoir if river is dammed). In freshened parts of sea, feeds mainly on benthic crustaceans. Does not feed while migrating upstream. At spawning sites, starts to feed again, mainly on insects, eggs and juveniles of other fishes, rarely on algae, seeds and other plant material.
Life History and Behavior
IUCN Red List Assessment
Red List Category
Red List Criteria
In the western Caspian Sea the landlocked population (in the Kura river) is thought be stable, and the anadromous population has declined, due to the lack of spawning sites and poaching, but it is still frequent in the southern Caspian tributaries in Azerbaidjan and Iran.
Overall, there is a continuing to decline due to expanding hydropower development and strong ecological impacts on Caspian and Aral Sea basins. It is suspected that the total population has declined by at least 30% in the past 30 years.
Relevance to Humans and Ecosystems
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