On a tracking expedition through the Bismarck Sea, scientists followed individual gray reef sharks as they navigated between shallow reefs and deep-sea canyons, their movements revealing something remarkable: an underwater architecture that channels nutrients and species in patterns as orderly as a highway system. Those shark routes became the blueprint for Papua New Guinea's bold announcement on May 13—the creation of a 214,000 square kilometer no-take marine sanctuary in the Western Manus, an area nearly the size of the United Kingdom and the largest of its kind in Melanesia.
What makes this sanctuary unusual isn't just its size. The Western Manus Marine Protected Area covers 6.7 percent of PNG's industrial fishing grounds and 10 percent of its industrial tuna fishing area—precisely positioned to harness what scientists call "spillover." When a no-take zone reaches sufficient density of marine life, fish and larvae move outward into adjacent waters where fishing is permitted. Research across large-scale marine protected areas in the Pacific and Indian Oceans shows that tuna catch rates increase by an average of 12 to 18 percent near protected boundaries. The sanctuary is engineered to generate exactly that effect, making the surrounding fishery more productive, not less.
The decision rests on foundations laid by a three-month National Geographic Pristine Seas expedition in 2024, conducted in partnership with PNG's Conservation and Environment Protection Authority and the Wildlife Conservation Society. Surveyors logged more than 700 reef fish taxa and over 300 species of hard corals. Coral reefs in the Western Islands ranked among the healthiest recorded in the Pacific, with schools of wahoo, rainbow runners and jacks moving through clear waters. But shark numbers were low—a well-established warning sign of overfishing. Deep-sea surveys documented something unexpected: species never before recorded in PNG, including the yokozuna slickhead, a large fish found at extreme depths, reinforcing the case for protection before extraction pressures intensify.
The sanctuary's boundaries were drawn to protect far more than sharks alone. Scientists traced the movement patterns of spinner and bottlenose dolphins, short-finned pilot whales, deep-diving Cuvier's beaked whales, scalloped hammerhead and silky sharks, and killer whales that return annually. Seabirds—black noddies, white terns, red-footed boobies, and Siberian sand-plovers—forage up to 200 nautical miles from their nesting sites across the same waters. All follow the same "marine highway," the underwater mountain ranges, ridges and canyons that concentrate nutrients and the species that depend on them.
The announcement arrived on the fourth day of the first-ever Melanesian Ocean Summit in Port Moresby, where more than 500 delegates from PNG, Fiji, Solomon Islands, New Caledonia, and Vanuatu gathered. These five nations have emerged as regional leaders in the global 30×30 campaign, which aims to protect 30 percent of the world's oceans by 2030. The Western Manus sanctuary would account for approximately nine percent of PNG's exclusive economic zone and anchor the Melanesian Ocean Corridor of Reserves, a network of national and joint-boundary protected areas spanning the region.
PNG's government will now begin the formal legal designation process. Lindsay Young, vice president of research at Pristine Seas, captured the vision: this isn't just a beautiful place, but a highly connected system where shallow reefs, deep-sea habitats and open ocean waters are linked, supporting species that move across them. The sanctuary arrives at a critical moment to protect those connections and ensure the long-term health of the ocean and the communities that depend on it.