Environmentalists in Australia are calling for a 50% reduction in the amount of tuna caught by commercial fleets in the South Pacific. They say that large-scale fishing by Asian, American and European trawlers will devastate stocks of bigeye and yellowfin tuna, which are prized ingredients in sushi and sashimi dishes. Global campaign group Greenpeace is calling for urgent action ahead next month's Tuna Commission meeting in Guam. From Sydney, Phil Mercer reports.

Environmentalists say tuna stocks in the South Pacific are on the verge of collapse from overfishing. They say the multi-billion-dollar industry is operating far above sustainable levels.

The annual catch of albacore, bigeye, skipjack and yellowfin tuna in the region is about 2 million tons. Campaigners want to see that figure cut in half.

Analysts estimate that there are 8,000 vessels involved in the region's tuna trade. They range from as far away as Japan, Korea, Russia and the United States.

The depletion of fish stocks worldwide has consequences for the marine ecosystem.

But Lagi Toribau of Greenpeace says large-scale commercial fishing is also endangering the economies of small island states that rely on tuna.

"We can comfortably say that for a lot of these fishing nations it's all about money and it's all about sustaining a global appetite for tuna, whereas on the other side," Toribau said, "there are the Pacific island countries who are trying to survive and trying to sustain a livelihood for them."

These concerns will be aired at the annual Western and Central Pacific Fisheries Commission that takes place in Guam next week.

The organization was set up in 2004 to look at ways to conserve and manage the region's tuna populations. It brings together the international fishing industry and governments from across the South Pacific, as well as representatives from China and the Philippines.

The Commission has been investigating the use of satellite-based systems to monitor the activities of trawlers.

Environmental groups are also urging action to reduce the effects of tuna fishing on wildlife.

Long-line fishing is a controversial technique that campaigners claim kills thousands of seabirds, turtles and sharks.