French Polynesia and the Cook Islands this month created adjacent shark sanctuaries spanning 2.5 million square miles of ocean, a move that reflects a growing trend to protect sharks worldwide and more than doubles the area now off-limits to any shark fishing.

As many as one-third of all shark species face some threat of extinction, according to the International Union for Conservation of Nature, in part because their fins are coveted for the Asian delicacy shark fin soup.

In the last few months, American Samoa and the Micronesian state of Kosrae have barred shark fishing off their shores, and the European Union and Venezuela have both prohibited the practice of cutting off a shark's fins while discarding the body at sea.

French Polynesia - a group of five major archipelagoes with more than 100 islands, including Tahiti - created the world's largest shark sanctuary of 1.5 million square miles of sea on Dec. 6.

The Cook Islands designated its own, which is equal to the size of Mexico at 756,000 square miles, on Dec. 19.

French Polynesia had established a moratorium on shark fishing and finning in 2006, but it exempted mako sharks to win over local fishing interests. More than 20 shark species, including hammerhead and thresher sharks, swim off its shores, according to the Pew Environment Group's global shark conservation program director, Jill Hepp.

Tekau Frere, a technical adviser to French Polynesia's environment minis–ter, wrote in an e-mail that a permanent ban, which will now include makos, reflects sharks' ecological, economic and cultural significance.

Sharks, she wrote, "have a high value in Pacific Island cultures. . . . They are both respected and feared."

She noted that fishing officials embraced the idea "since they see this protection as a great value in their efforts to get a green or sustainable label for our tuna fisheries. What is more, healthy and well-protected ecosystems attract tourism."

Teina Bishop, who serves as the Cook Islands' minister of marine resources, said in a statement that his nation was proud that so many nations in the region were acting to ensure viable shark populations: "We join our Pacific neighbors to protect this animal, which is very vital to the health of our oceans, and our culture."

"In just a few short years, there has been a fundamental shift in the way that sharks are perceived," Hepp said, adding that concern over the effects of losing sharks "is now far more frightening than their misguided reputation. With shark fishing now legally prohibited, we are hopeful that sharks now have the protections they need to recover in the same way that wolves and bears have returned in national parks on land."

Traditionally, French Polynesians rarely ate shark meat, Frere wrote, which kept the country's annual shark catch modest. "However, with the development of shark finning abroad, the demand for fins skyrocketed in late 1990s early 2000s," she wrote.