"It does not look good, when I look at the diagrams there is a decrease (in catches) every year," he told Reuters.

The Secretariat of the Convention on International Trade on Endangered Species (CITES) earlier this month approved tighter export quotas on the precious roe of all but one species of Iranian sturgeon.

Environmentalists estimate sturgeon stocks around the Caspian states of Iran, Azerbaijan, Russia, Turkmenistan and Kazakhstan have slumped about 90 percent since the late 1970s.

"The main problem is the overfishing since the break-up of the Soviet Union," Keivany said.

Lawlessness in former Soviet states has ushered Mafia-style gangsters into the lucrative hunt for the Caspian's "black gold," green groups say.

Aficionados will pay more than $2,000 for a kilogram of "buttery" caviar from the prized Beluga sturgeon.

Iran's Beluga export quota for 2003 was sliced nearly 28 percent. Environmentalists have severely criticized Iran for continuing the condemned practice of open-sea fishing.

Falling exports have spurred Iran's caviar prices in the global market. The Abrar-e Eqtesadi financial newspaper reported this week prices reached nearly $587 a kilogram in the five months since March 21, a $40 year-on-year increase.

"Pollution is also a problem, especially with the discovery of oil that has made the situation worse," Keivany added.

Sturgeon, long-snouted denizens of the deep, can live more than 50 years with the Beluga sometimes reaching 100. Nowadays scientists say life expectancy is 20 to 30 years.

Reza Marandi, university lecturer in Tehran and expert in oil pollution, said a desire to make money from the Caspian's resources was trampling on environmental concerns.

"Caviar production is now very low - oil spills have affected the sturgeon. People are just thinking economics," he said.

ROOM FOR OPTIMISM

However, CITES Deputy Secretary-General Jim Armstrong, told Reuters he believed co-operation between Caspian states on managing stocks and stopping poaching was now paying dividends.

In fact, CITES has figures that suggest the decline of sturgeon populations had been halted and has approved an inching up of export quotas for the Caspian Sea as a whole.

"There is now huge co-operation," he said.

Keivany said it was hard to see a solution.

"In an ideal world people would stop fishing sturgeon for a while but this is impossible: so many people depend on them for their livelihood, some countries do," Keivany said.

Caspian states have embarked on an ambitious network of hatcheries which release young sturgeon to replenish stocks.

CITES has commended new systems that improve the survival chances of the young sturgeon but Keivany said the hatcheries had yet to make a major impact.