Sturgeons are long-lived fish built on a slow schedule. Female belugas typically reach first spawning somewhere between about fifteen and twenty-five years of age, and after spawning they do not return the following season; intervals of several years between spawning events are normal.
That biology multiplies the effect of harvest. A fishery that removes large mature females removes decades of accumulated growth and the future spawnings that fish would have made, and recruitment cannot rebound within a few seasons. Dams on the Volga and other tributaries compounded the problem by cutting adults off from historic upstream spawning gravels. The species is now assessed as Critically Endangered, and international trade in its caviar is regulated under CITES.
Historic reports of belugas over seven metres and 1,500 kilograms circulate widely but are poorly documented; the largest well-attested fish are smaller, and no modern population contains animals approaching the old records.