Over-fishing has seen the population of sturgeon drop by 90 per cent and pushed prices up nearly sevenfold to €10,000 (£8,350) per kilogram – or £835 for enough to make a sandwich.
The Caspian Sea is home to 80 per cent of the sturgeon bearing the three most sought after varieties of caviar – Beluga, Osetra and Sevruga. Small quantities are also found in the Black Sea.