Extreme poverty is driving Russians in the Pacific region to poach salmon to unsustainable levels, a UK group says.
Red gold: The illegal caviar trade sustains many thousands
Television Trust for the Environment says the Kamchatka peninsula is home to a massive population of wild salmon.
But foreign demand for caviar made from salmon roe is insatiable, TVE says, and poverty leaves the people of Kamchatka few other ways of earning a living.
It says the rapid demise of wild salmon in the area will determine the fate of the species across the globe.
The extent of salmon poaching in Kamchatka is featured in Death Roe, a film in the Earth Report series made by TVE and shown on BBC News 24, BBC One and BBC World.
Click here to watch the Earth Report film Death Roe.
Kamchatka was a closed military region during the Soviet years, subsidised by Moscow. But that stopped in 1989, and desperate poverty ensued.
The film says many people in Petropavlovsk, the peninsula's capital, depend directly or indirectly on the caviar trade, although it is officially restricted.
Fish are caught and left to rot
One poacher, Inga Arsenuk, is a black market caviar buyer who used to make the equivalent of $50 a month as a schoolteacher.
He tells the crew: "Now I make maybe $1,000 a month, or a little bit less... Poachers don't pay taxes, they don't pay social security contributions.
"They just take the caviar and leave the fish to rot. The environment suffers more and more."
On the open market in Petropavlovsk salmon caviar fetches $15 a kilo, but in Moscow it sells for five times as much.
Japanese experts visit Kamchatka to make sure they get the caviar in the way they prefer, still in the egg sac lining the salmon's womb.
Oleg Pustovit is a biologist from Moscow State University working in Kamchatka for the US-based Wild Salmon Center. He believes a disaster with global consequences is imminent, with poaching only part of the problem
Caught too young
He tells TVE: "Kamchatka is the last remaining preserve for salmon in the world. This is the only place all kinds of wild salmon live.
"Soon oil will be extracted on the ocean shelf. A gas pipeline is being built. People have a growing impact on nature. If we accept things as they are, if we don't fight it, we face ecological crisis."
Caviar smuggling is reckoned to generate $1bn a year in Kamchatka, and conservationists say it cannot continue at the present rate.
Local sales earn little: Foreign buyers are best
Apart from the highly organised poaching gangs there are individuals involved, each doing little damage but together steadily depleting the rivers of fish before they can reproduce.
TVE foresees another problem: the government-owned gas company is building a pipeline across the peninsula, opening a service road connecting the wilderness rivers for the poachers.
Evgeny Svyazhin of the United Nations Development Programme tells TVE: "It is useless to constantly chase poachers trying to fight with them in this way.
"I think we have to do something to create economic incentives for people who live in these areas in order to change the situation."
Dr Jack Stanford, a University of Montana conservation ecologist, says: "It's time to put a stake in the ground and help the Kamchatkans preserve this resource so that we can come here and see how this wide array of fishes uses these very unique complex river systems.
"We can take that knowledge back to North America and use it to begin to restore our rivers in a more robust way. If we lose Kamchatka, we've lost it all."