Last month, Indonesia established the world’s largest sanctuary for manta rays – those enormous, finned fortresses that can reach nearly 30 feet across. For the first time, manta ray hunting and export is banned within the entire 2.3 million square miles of Indonesia’s exclusive economic zone.

The sanctuary is a victory for conservationists and the manta rays, as Indonesia was home to some of the largest ray fisheries in the world.

But the decree may not have been motivated solely by the plight of the rays, whose populations are dwindling in the archipelago. As ever, money talks. A study published last May in PLoS ONE calculated the measure of a manta and concluded the immense rays are worth much more alive than dead. For starters, the study reports that Indonesia earns an estimated $15 million in manta ray tourist revenues annually – compared to the ray fisheries, worth about $500,000. And, it concluded, a living manta ray is worth almost $2 million in tourism revenues over the course of its roughly 25-year lifetime (this estimate was based on the island of Yap, which has one of the best known manta ray tourism spots and a stable population of 100 rays).

Though shaped like B-2 stealth bombers with mouths large enough to swallow a human, manta rays are gentle and social animals. Their tendency to feed near the ocean’s surface and interact with humans makes swimming with them a sought-after experience.

“To spend time in the company of a manta ray is both a humbling and incredibly moving experience,” said photographer Shawn Heinrichs, whose work appears in the gallery above. “They are massive, powerful creatures, yet are incredibly gentle and curious. If approached correctly, they will interact and dance with you for hours on end.”

Unfortunately, those same friendly tendencies make the rays easy targets for hunters, whose chief challenge lies not in spearing them but in wrestling the massive creatures aboard fishing boats. Slow to both mature and reproduce, manta rays don’t replenish their populations as quickly as some other species; in terms of life history strategy, the rays are more like humans than sharks and fishes – it takes them a decade to mature, and they produce one pup every 2-5 years. Because of that, it doesn't take long to hunt a population to depletion.

The fishermen aren’t butchering the rays for their meat. Those thousands of pounds of flesh are essentially worthless – an entire ray sells for $40 in Sri Lanka and $200 in an Indonesian market. Instead, the fishermen are after the mantas’ gills, which are sold to traders who shunt them into Chinese markets. Here, gills can sell for $500 per kilo, and are used in medicinal tonics said to salve anything from chickenpox to cancer. But like rhino horns or vulture parts, the manta gills really have no medicinal virtues – even according to practitioners of traditional Chinese medicine.

Of course, now that the sanctuary legislation is in place, the difficulty lies in enforcing the new regulations. Desperate for money and for resources to feed their families, some fishermen will likely turn to ray poaching. The struggle to survive is a problem that Heinrichs witnessed first-hand during his trips to the islands to document the rays and the many roles they play in the region. “The people of Indonesia are some of the most kind, warm and welcoming people I have ever spent time with,” Heinrichs said. “Even those that hunt mantas are not bad people. Like us, they want to provide for their families food, shelter and educational needs.”

All photographs copyright Shawn Heinrichs for WildAid & Conservation International. More photos and updates here.