The over-exploitation of global fish stocks has reached dramatic levels and Asia, a leading producer and major consumer of seafood, is at the heart of the problem. An international environmental group says pressure by consumers and retailers can play an important part in making fishing regions sustainable. Claudia Blume reports from VOA's Asia News Center in Hong Kong.

The United Nations' Food and Agriculture Organization estimates that three quarters of fish stocks worldwide are fully exploited or depleted. Over-fishing has ruined biodiversity in many parts of the world, and it threatens food security and the livelihoods of many people.

The problem has hit Asia harder than some other regions in the world. The Asia-Pacific region is not only the world's largest supplier of fish, but more sea products are consumed here than anywhere else. Japan is the world's biggest importer of fish in terms of value, for example, and China, in terms of volume.

Shark's fin is an expensive and sought after delicacy in Hong Kong and China. But Shelley Clarke, an Asia-based fisheries specialist, says it is difficult to find reliable data on how many sharks are being caught to produce shark fins.

Speaking at Hong Kong's Foreign Correspondents Club on Wednesday, Clarke said shark catches are often not recorded, for a number of reasons. One is that the sharks' bodies are often thrown back into the sea once the fins are cut off.

Clarke looked at Hong Kong seafood markets and did her own calculations - and what she found was surprising.

"Using markets from Hong Kong, I was able to estimate that shark catches are three to four times higher than we previously thought," she said.

John White is the development director of the Marine Stewardship Council, an international environmental group. The organization has developed a certificate specifying those regions in the world that are fished and managed in a sustainable fashion.

White says if people in Asia want to continue having fish on their plates, fishing practices in the region have to change. And he says retailers and consumers can play an important role in bringing about change.

He says an increasing number of major retailers worldwide - such as Wal-mart in the United States - have committed themselves to selling only fish and seafood carrying Marine Stewardship Council certification.

"You got demand pressure from consumers and retailers saying, 'We want this sort of material,' [and] suppliers saying, 'If we want to get into this market, we have to get certified.' So we have both demand and supply pushing in the same sort of way," said White.

White says that some retailers in Asia have begun selling seafood with the eco-label. But he says no Asian fishing regions have yet been certified, meaning over-fishing in the region remains a serious problem.