Cesar Sabogal / AFP - April 29, 2007 09:05 EST

When Colombian naval officials seized two tonnes of shark fins in a boat off the Pacific coast last week, they threw a spotlight on a huge black market serving hungry Asian markets which is blamed for pushing some species toward extinction.

Asian consumers prize the fins for use in making status-symbol soups -- and one pound (450 grams) of fin can fetch 300 dollars. Some shark-fin soups go for as much as 90 dollars a bowl in the countries where the dish is most popular: Malaysia, Indonesia, Japan, Taiwan, Singapore, South Korea and Thailand.

The Colombian-flagged vessel was arrested 18 nautical miles from Malpelo island, a UNESCO natural world heritage site off Colombia's Pacific coastline.

It was crammed with the fins of endangered sharks including hammerheads, silkies, oceanics, white fins, black fins, fox shark and reef shark.

Authorities arrested the crew on board and impounded the boat.

Cartels led by Japanese and Colombians are said to be behind the big business of shark fins in the Colombian Pacific.

"The Asians control the routes and the markets, and they intimidate the local fishermen and distributors who are paid a pittance per kilo," about 30 dollars, said a Colombian official with the Environmental Crimes Investigation Group, who asked not to be identified.

Biologist Sandra Bessudo, who leads the independent Malpelo Foundation, told AFP the illegal fishing situation was so critical that a species believed unique to the waters around sanctuary, the sol-rayo or ragged-tooth shark (Odontaspis ferox), was in danger of dying out.

The foundation says that in 2003 alone, more than 13 tonnes of shark fins were exported to Hong Kong, the equivalent of some 67,000 dead sharks.

And an average of 350 ships -- mostly from Japan, Taiwan, Ecuador and Mexico -- fish for the prize in Colombian waters.

"There just is no doubt that the shark population has declined considerably in Colombian waters in recent years," said Andres Navia, director of the non-governmental group Squalus fighting for protection of those sharks.

"We are calling on authorities to protect those that are still alive; it is an extremely urgent matter."

Sharks are not the only groups under threat, by any stretch, in Colombia. Marlins, large turtles and mollusks also are in danger.

Julia Miranda, director of Colombia's natural parks, said that after illegal drugs, weapons trafficking and kidnapping, the unlawful trade in animal species moved the largest amount of dirty money in the South American country.

Fishing is banned in the Malpelo wildlife sanctuary, an area which sprawls over 8,575 square kilometers (3,311 square miles). The island area is also a sanctuary for birds, and a diving paradise.