Out in the northern reaches of the Caspian Sea, where Russia borders Kazakhstan, there's a war going on - and it's all over a fish. An epic struggle is being played out between competing gangs of poachers and the police as they try to protect one of the world's largest and most ancient fishes.

This week, Earth Report visits the last stronghold of the sturgeon and uncovers how it has been brought to the brink of extinction after 250 million years on the planet and what can be done to save it.

No ordinary fish

The sturgeon's black glistening roe, better known as caviar, used to be eaten by ancient Egyptians and has remained a prized and valuable fish. Today, it's sold all over the world for sky-high prices. Just one beluga, brimming with caviar, can fetch up to 30,000 US dollars on the international market.

Fishing to death

90% of the world's sturgeon is now found in the Caspian Sea where commercial fishing began as early as 1800. During the Soviet era, sturgeon fishing and caviar production became truly industrial in scale. By the late 70s over 25,000 tonnes of sturgeon were caught each year.

The sturgeon is a slow-growing fish - reaching maturity after 15 to 20 years - making it extremely sensitive to over fishing.

Until 1991, control of the Caspian was shared between only two countries. Since the break-up of the Soviet Union, the fate of the sea has been in the hands of Russia, Azerbaijan, Kazakhstan, Turkmenistan, and Iran.

Now, decades of over fishing has seen numbers of sturgeon drop to a critical level and blame for this has shifted to the illegal 'freelance fishermen'.

Although each of the five countries bordering the Caspian has internationally agreed quotas on the amount of sturgeon that can be caught, scientists from the Caspian Fishery Research Institute estimate poachers in the former Soviet waters are catching at least 10 times the legal amount of sturgeon. At current levels, the sturgeon may disappear in 4 to 5 years.

Hard currency

With an average monthly wage of 40 US dollars and a kilo of Beluga caviar selling at around 100 US dollars, it's hardly surprising illegal fishing has increased dramatically in recent years.

Enforcing quotas isn't easy. The Volga delta alone is vast - over 20,000 square kilometres - with literally thousands of creeks and channels. And with such big money involved, the standoff between poachers and the police has become violent.

But the net is now tightening around the poachers. Since the Russian Prime Minister, Mr Kasianov, visited last spring there has been a major crackdown on illegal fishing and even the small official catch has been severely restricted.

Now so rare, only 100 sturgeons a year are said to be caught in the Caspian and scientists are calling for a complete ban on sturgeon fishing.

Starting and enforcing a ban will depend on the governments of the Caspian countries agreeing to work together, which takes time - a commodity the sturgeon is running out of.

Saving the sturgeon

Ironically, it may be big business that will save the sturgeon.

The Azerbaijan State Fisheries Corporation is on the verge of being privatised and a bold new venture is waiting in the wings.

The Caspian Fish Company, a huge 80 million dollar fish processing business on the outskirts of Azerbaijan's capital, Baku, aims to process 300 tonnes of fish a day, plus caviar.

Along with fishing and processing rights, the company will play an important role in developing fish stocks by upgrading local run-down hatcheries along the shores of the Caspian. In three years the company aims to increase hatchery production from 20 million to 100 million fry a year.

To combat poaching, the company aims to introduce a system of fishing licences. Fishermen caught without a licence will face prosecution.

In today's economic climate, where poaching is rife, controlled fishing by monopolies may be the only answer. But is this enough?

Even with an immediate moratorium the future of the sturgeon is not secure. For a species that has existed since the time of the dinosaurs the next few years will ultimately decide its fate.