Matthew Rivera has been spearfishing for tuna in Palau's clear blue waters most of his forty or so years. It's a big part of life here in this tiny Southern Pacific archipelago 600 miles east of the Philippines. "Because us here in Palau, we can't eat meat everyday," Rivera says. "We can't eat chicken. We have to eat fish. It's what we grew up with as little kids."

Palauans are lucky. This part of the Pacific is home to the world's last healthy tuna populations. In recent years the global demand for tuna has exploded, and populations elsewhere have crashed. In fact a major study released this month estimated that the population of one key species, Pacific bluefin, has dropped by 96 percent in recent decades. And a single Pacific bluefin fetched a record price of nearly one-point-eight million dollars this month in Tokyo.

The combination of collapsing stocks and skyrocketing prices are prompting tuna boats to flood into the waters around Palau and its neighbors. Some of the fishing is legal, but not all of it. And as a marine policeman here, Rivera works to protect Palau's nearly quarter-million square miles of ocean from illegal fishing.

But there's a problem: the country has only one patrol boat. And when it comes to enforcement, Palau's President, Thomas Remengesau Jr. says that's "the big hole in the bucket" in his country's efforts.

"Every time our one patrol boat goes to the southwest islands, it's almost a given thing that they're going to catch some poachers out there'" Remengesau says. "Every single time."

That's one reason Palau recently banded together with seven of its South Pacific neighbors to try to protect their tuna populations better. They even worked with regional authorities to largely ban big tuna operations from the international waters between their countries.

It's an unprecedented arrangement. But enforcement is still a constant battle. So Palau has called on outsiders for help, including organizations like Greenpeace, which now helps patrol the waters around the country.

On one recent excursion over international waters about 500 miles offshore, a Greenpeace helicopter carrying a Palauan Marine Officer and Greenpeace activists spotted three tuna boats. The passengers suspected two of them were moving tuna onto the third, for transfer to market.

It's a process called transshipment, which can obscure the tuna's origins, making it impossible to track where the fish was caught. Conservationists call it tuna laundering.

As the chopper flew in closer, a bucket of fish could be seen swinging from one of the boats onto the deck of its neighbor, leading one of the Greenpeace crew to exclaim, "Caught in the act!"

The receiving vessel was a Cambodian-flagged refrigerator ship named the Heng Xing 1. When the activists and the Palauan official boarded the ship a few hours later and descended a frosty ladder into its dark, icy belly, they found the hold jammed with tons of frozen skipjack and yellowfin tuna.

The captain of the vessel admitted that he didn't have a license on board, although he claimed that the company that operated the ship back in Cambodia did.

It's impossible to know whether the fish in the Heng Xing 1's belly were caught legally, but the transfer of the fish to the ship was illegal. Although moving fish at sea is a common practice, authorities here in Palau require that boats offload only in port so they can track the tuna.

And as a Cambodian-flagged vessel, the Heng Xing had no right to work here at all.

But since it was operating in international waters the Palauan officer riding with Greenpeace couldn't bust the ship. All he could do was report the incident to the regional fisheries authority.

A few days later, the monitors came across another of the boats that took part in the illegal transshipment. Palauan Marine Officer Earl Benhart says it seems pretty clear the boat was up to no good. He says the Philippines-registered boat was transiting Palau with no vessel name, no call sign and no log book.

But again, Officer Benhart could only report the ship. The crew was frustrated, but not surprised. Jurisdictions on the ocean are notoriously complicated, so even boats that are caught red-handed go free because the boarding nation lacks the authority to enforce international law.

Greenpeace activist Farah Obaidullah says the incidents show the need for an INTERPOL for the oceans. "Countries should be able to enforce international law on boats that are not necessarily registered to their country, Obaidullah says. "Because otherwise, this is what happens."

Short of that, host countries like Palau will have to depend on the willingness of bigger fishing countries like the Philippines, Taiwan and the United States to make their boats play by the rules.

After the incident with the undocumented Philippine tuna boat, its home country launched an investigation into its activities.

And the Philippines' top fisheries official Asis Perez says his country doesn't sanction illegal fishing anywhere.

Perez says there's no debate that there's a problem. "We may not be able to prevent," he says. "But we will never ever tolerate an illegal action by our citizens in whatever countries they are."

Perez says the Philippines is trying to step up enforcement and plans to add more boats to monitor their high seas fishing fleet.

But self-policing has generally failed to prevent overfishing, on the high seas or elsewhere. And with tuna prices on the rise and stocks crashing elsewhere, the pressure on Palau and her neighbors is only likely to increase.

President Remengesau says the effects are already noticeable.

"We're living the depletion of stocks of fish," Remengesau says. "We used to fish very close to shore, now we have to go miles away. And this is only the window of what will eventually be affecting everybody."

This report was produced in collaboration with the nonprofit Food & Environment Reporting Network, an investigative reporting nonprofit focusing on food, agriculture and environmental health.