By Christopher Pala

A bold move by eight Pacific island nations to preserve the world's last large stocks of tuna is expected to face strong resistance this week at a meeting of the Western and Central Pacific Fisheries Commission (WCPFC) near Honolulu, Hawaii.

By leveraging agreements with foreign fishermen in their own territorial waters, the islands have banned fleets that fish with purse-seine nets--mechanized nets that can capture entire schools of tuna in a single haul--from operating in a region of international waters roughly the size of India. The area, known as the Eastern High Seas (see map), will still be fished by hook-and-line, which is considered biologically more sustainable. The islands will also cut the time that purse-seiners can spend fishing in their territorial waters by nearly a third. The restrictions, agreed to by the eight nations in April, are scheduled to take effect on 1 January 2011.

Marine biologists say the development is a major step forward for efforts to halt the global decline of bigeye, yellowfin, skipjack and other tropical tuna species. In October this year, Britain turned the entire Exclusive Economic Zone around the Chagos Islands, in the center of the Indian Ocean, into a no-take zone, making it the first area rich in tuna that has been closed to fishing. At 3.2 million square kilometers, the Eastern High Seas is six times larger.

"These are the most far-reaching ocean-conservation measures ever," says Daniel Pauly, a leading fisheries scientist at the University of British Columbia in Vancouver. "For the first time since man has been fishing out the open oceans, we're going to see a reversal of the decline of pelagic species in two big areas."

At the meeting this week, the world's major fishing nations, including the United States, are expected to challenge the measures. By treaty, the United States is technically exempt from the restrictions, but two years ago it chose to side with the island nations in the closing of two smaller pockets of international waters to foreign fleets.

This time, conference sources predict a less sympathetic attitude. "We're not totally settled in our positions," says Charles Karnella of the National Oceanic and Atmospheric Administration, who heads the U.S. delegation. "We're renegotiating our treaty and how the closure is dealt with will be part of our talks."

Ships from the United States operate under the South Pacific Tuna Treaty, in which the U.S. government pays most of their license fees and provides $18 million in foreign aid to 14 island nations. In exchange, the U.S. fishing fleet, now set at 40 ships, has unlimited access to the region.

Should the United States decide not to abide by the new closures, U.S. purse-seiners could find themselves fishing there virtually alone, contributing to the depletion of bigeye tuna at a time when fisheries scientists are calling for a 30 percent reduction in bigeye catch to avoid the collapse of stocks, which have fallen from 1.2 million tonnes to 500,000 tonnes since 1952 (see "Bigeye at risk").

Marine havens

Sari Tolvanen, a Greenpeace International oceans campaigner attending the meeting, points out that the closure area is bordered on both sides by no-take areas created when former President George W. Bush named the islands of Wake, Johnston, Jarvis, Howland, Baker and Palmyra Atoll as a Marine National Monument in January 2009.

"It would be shameful if the Obama administration did not follow the Bush administration's example and opted out of the conservation measures taken by the Pacific island nations," she says.

The decision to end purse-seining in the Eastern High Seas was taken by the Parties to the Nauru Agreement (PNA), eight Pacific island nations in whose waters 80 percent of the region's tuna is fished. They comprise the Federated States of Micronesia, Kiribati, the Marshall Islands, Nauru, Palau, Papua New Guinea, the Solomon Islands and Tuvalu.

Although no nation can legally restrict fishing in the high seas, the PNA countries have jointly amended the standard contracts they sign with foreign fleets with a stipulation that the fleets refrain from fishing in some international waters, in order to remain eligible for licenses within waters directly controlled by the islands.

The regulations are made enforceable by the use of radio transponders, which reveal the positions of the licensed ships at all times. The first such measures, which began in 2008, closed smaller pockets of international waters that were being used as refuges for vessels fishing illegally. The extension of the ban to the Eastern High Seas is seen as potentially far more important because this region is large enough to have an impact on species preservation.

Officials from the PNA say that once they have succeeded in ending purse-seining in the Eastern High Seas, they will ban longliners--a different type of fishing vessel that catches about the same tonnage as a purse-seiner--from the area, effectively turning it into the world's largest marine reserve.

An important factor that will determine the effectiveness of the ban is the extent to which fish stay within the protected area. John Hampton, head of the fisheries program at the Secretariat of the Pacific Community (SPC), co-authored a study conducted farther to the west. This found that half the skipjack tuna there spend their entire lives within a radius of 675-750 kilometers (J. Sibert & J. Hampton Mar. Pol. 27, 87-95; 2003). A new SPC study under way in the Central Pacific focuses on bigeye tuna, with 15,000 tuna tagged so far, he says. It will provide information on tuna movement and mixing with adjacent areas, rates of mortality and other important population parameters.

"With good tagging data, we'll have a better understanding of the way the tuna move, and that will help us predict the effects of the closures on the population levels," he says.

Pauly predicts that because the individual tuna that do not travel long distances will survive in greater numbers, their offspring will have a genetic advantage over those that do range more widely, enhancing the conservation value of the refuges. "It's going to make the islands and the seamounts much more important, more attractive to these fishes," Pauly says.

Because this is the first time that anyone has tried to end fishing in a large body of international waters, it could establish a precedent, observers say. Until now, the world's seas have been fair game to the international industrial fishing fleets, with the commissions that theoretically have the power to restrict them strongly influenced by the fleets themselves.

"The closures would raise legal issues if they weren't justified as conservation measures," says Satya Nandan, chairman of the WCPFC. "Our stocks are relatively healthy and we want to keep them that way."