On Sunday marine ecologist Pelayo Salinas was on his way back from a 12-day research mission on a Galápagos National Park patrol ship when at 6 a.m. the captain spotted a vessel on the radar. Access to these waters is restricted, so they radioed the vessel to find out what it was up to.

No response. Salinas, who works with the Charles Darwin Foundation, and a Ecuadorian Navy officer who was also on board tried again. Still no response. They warned the vessel that the law requires them to respond. Silence.

Then Salinas and three others jumped in a 13-foot inflatable boat that had been donated to the park and took chase. They’d identified the vessel as Chinese and strongly suspected it was involved in illegal fishing.

This part of Galápagos National Park—a marine sanctuary where absolutely no fishing is allowed—has the greatest abundance of sharks known in the world. It’s this that has made these waters a target of fishermen looking to supply Asian markets with shark fin and shark meat. Worldwide, shark populations are declining, with more than a quarter of sharks and related species considered to be threatened with extinction.

Their little boat, a Zodiac, wasn’t designed for hot pursuit, however, and they weren’t able to catch up. They abandoned the chase and reported the Chinese boat to park headquarters. At the park's control center, park authorities and the Ecuadorian navy identified the vessel in their electronic surveillance system and sprung into action, says Walter Bustos, the director of Galápagos National Park.

Soon a navy helicopter and coast guard boat were dispatched, along with Galápagos National Park rangers. They caught up with the ship, a China-flagged vessel called Fu Yuan Yu Leng 999. What they found stunned them.

“There were thousands, if not tens of thousands, of sharks,” Salinas says. “This is going to be historic. The biggest seizure of sharks in the history of the Galápagos, for sure.”

The crew of 20 have been arrested, and the Ecuadorian authorities are planning a full accounting of the ship’s inventory. It’s illegal to cross the marine sanctuary’s waters without a permit, and it’s also illegal to catch, trade, or transport sharks there. Authorities do not yet know where the fish were caught, according to a statement from Ecuador’s Ministry of Environment.

The vessel is a “mothership,” or reefer, which collects fish from smaller fishing boats, allowing them to stay out at sea longer. It’s more than 300 feet long with six cargo bays, several of which were completely full, he says. The ship’s log says there are about 300 tons of fish on board, according to the statement. Salinas himself hasn’t been on board yet, but in photos of the holds he identified endangered scalloped hammerheads and silky sharks, as well as tuna.

In a call with National Geographic, Bustos praised those who helped bring the vessel in. “The special effort of the army of Ecuador and the park rangers—they are the real heroes of this story.”

CAUGHT BY PURE CHANCE

“Sadly, this is day-to-day business on the ocean,” Salinas says. “There are thousands of these ships roaming the waters.”

The incident highlights the ongoing problem of illegal, unreported, and unregulated fishing that occurs even in the world’s most protected waters.

It was pure chance that the vessel was caught, Salinas says. For some reason (likely by accident, he suspects), it had its AIS—an automatic tracking system used by all ships—turned on. Ships engaging in illegal activity, for obvious reasons, turn them off. That likely lapse helped law enforcement track the vessel down.

Despite its high-profile status in the tourism and scientific worlds, Galapagos National Park doesn’t have all the resources it needs to protect the ecosystem.

“Resources are limited,” Salinas says. “The bad guys are every day making more money. Patrolling is expensive, especially for a county that is in economic crisis.” He points to the Zodiac as an example. If they’d had a proper boat intended for law enforcement, they could have caught up with the vessel when they first spotted it. (Salinas has started a crowdfunding page to raise money for two speed boats for the park.)

The arrested crew could face up to three years in prison, and conservationists are hoping this case will be aggressively pursued. China is Ecuador’s largest creditor, providing some 60 percent of the government’s funding, and critics have accused Ecuador of being lenient with China when it comes to protection of timber and other natural resources in the Amazon rain forest.

“Ecuador showed leadership in its vision” by establishing the marine protected area, says Enric Sala, a National Geographic Explorer-in-Residence who led a Pristine Seas expedition to the Galápagos. “Now it needs to show its commitment by enforcing the law."

At a press conference today, Ecuador’s Minister of the Environment, Tarsicio Granizo, said the government is committed to doing so. “Our policy is zero tolerance for the transport and trafficking of protected wildlife,” he said.

Galápagos National Park and the Charles Darwin Foundation receive funding from the Lindblad Expeditions-National Geographic Fund and the National Geographic Society.