Caviar like this is going to be in even shorter supply

It follows figures that show beluga sturgeon stocks in the Caspian Sea have fallen by 90% in the past 20 years.

The destruction of spawning sites, pollution and the collapse of the regulated Soviet system have all played a part.

But possibly the single biggest reason has been poaching - something that has increased as Soviet-era restrictions have disappeared.

So the ban which has now come into force on commercial fishing and the export of black caviar will be effective only if the Russian authorities put greater efforts into stopping the poachers.

Rewards for poachers

The rewards for the poachers are high.

Caviar is regarded as a delicacy on the dinner tables of the wealthy; a kilogram can sell for up to $4,000 in Western Europe and the USA.

The temporary bans have been introduced following a meeting in Paris last month of the Convention on International Trade in Endangered Species.

Russia now plans to take about 250 tonnes of sturgeon from the northern Caspian Sea this year - just over half of its planned target of 450 tonnes.

And these fish will be used for breeding, in the hope of going some way to replenishing stocks.

Apart from being good news for the sturgeon themselves, Russia's moratorium on exporting caviar will please Iran.

Caviar production there has been much better managed in recent years, and Iran may well be able to take advantage of the gap in the market caused by the Russian move.