In February, fishermen in Sri Lanka set up a fleet to demand further efforts by the government to protect the shrimp-rich northern waters of the island nation from poaching by Indian fishermen.

Sri Lankan fishermen say they’ve lost business, and some have lost their lives in confrontations with foreign crews.

The protesters demanded more action from the government, even as Sri Lanka’s navy has used force to guard its fisheries – destroying Indian fishing gear, charging at the vessels, and in at least one violent episode, firing shots. Five Indian fishermen were reportedly killed last year in encounters with the navy, although Sri Lankan authorities deny they killed or shot at crews, and say they were not the aggressors.

"The intensity is increasing, the level of violence is increasing, deaths are increasing," said N. Manoharan, who has researched the conflict as director of East Asian studies at Bangalore’s Christ University. Warnings and arrests, he said, have failed to keep Indian trawlers from crossing into Sri Lankan waters – in part because their shores are overfished. "They are so desperate for the catch, and they go and lose their lives."

This 600-mile stretch of the Indian Ocean is far from the only place where tensions over fishing run high. Elsewhere in the region, fishermen in India and Pakistan are also entangled in an ongoing boundary dispute between the two nations in the Arabian Sea. According to Indian news reports, Pakistan’s maritime authority has shot at Indian fishing boats at least twice in the past two years.

Around the world, from Sri Lanka to Argentina to the South China Sea, the ocean has become an expanding front in the armed conflict between nations over illegal fishing and overfishing, practices that deplete a vulnerable food source for billions of people worldwide. Jessica Spijkers, a researcher for Australia’s national science agency, found a rise in global fishing conflicts when she studied a four-decade period ending in 2016. Conflicts this century, she said, often involved claims of illegal and overfishing. Her analysis included nonviolent disputes that sometimes precede the outbreak of violence.

An Associated Press (AP) review of conflict databases compiled by nongovernmental organizations (NGOs), government tallies and media reports found in the past five years more than 360 instances of state authorities ramming or shooting at foreign fishing boats, sometimes leading to deaths.

During that same time, another 850 foreign fishing boats were seized by authorities and systematically crushed, blown up or sunk.

The figures cover incidents across six continents but are likely an undercount since no single entity tracks violent conflicts over fishing rights worldwide. The AP analysis did not include routine citations and arrests but focused on where and how violence has escalated in fishing grounds around the world.

Environmental and national security experts say countries that depend on fishing both as a source of food and commerce are at risk of greater conflict in the coming years. Already, industrial fishing boats extract droves of fish from the sea, with distant-water fleets from China and other countries roaming far beyond their domestic waters in search of stocks that have been depleted closer to home.

The search for new sources of fish comes as nations are tasked with feeding growing populations and climate change further endangers ocean life.

"It is getting significantly worse," said Johan Bergenas, a World Wildlife Fund (WWF) expert on oceans who first warned of a rise in global fishing conflicts five years ago.

"We are now seeing armed conflict and tensions and strains as a result of fish stocks and competition over in West Africa, in the West Indian Ocean, in Latin America," he said. "There’s going to be conflicts and armed engagements over these incredibly important fish stocks around the world."

In early February, the 400-foot United States Coast Guard Cutter Stratton docked in Fiji and welcomed three local officials aboard. For one week, the combined crew toured the oceans around Fiji’s islands in search of fishing boats that might be flouting the rules – boarding eight boats and flagging 22 customs and fishing violations.

Fiji’s exclusive economic zone is an area of water 70 times larger than its landmass. Vilisoni Tarabe, a fisheries policy officer at the WWF office in Fiji, said many Pacific island countries suspect fishing boats of catching more tuna or sharks than they report.

"We don’t always have the capacity or resources," he said, to "monitor the activities that go on those fishing vessels."

This sheer size of the ocean is partly what makes fishing enforcement so difficult – what Capt. Stephen Adler, the Stratton’s commanding officer, calls it "the tyranny of distance."

"What we do is we help provide those islands the support and the capabilities to go out and target those kinds of issues that they’re seeing out on their waters," Adler said.

The U.S. partnership with Fiji is one of 11 between the U.S. and Pacific Island countries, with a possible 12th on the horizon – each meant to stave off the economic collapse and regional instability that could follow if waters are fished to depletion. In a 2020 report, the service for the first time listed illegal, unreported and unregulated fishing ahead of piracy as the leading security issue at sea – even a possible threat to world order.

"It’s incredibly important to make sure that these regions stay stable," said U.S. Coast Guard Lt. Cmdr. Kristen Caldwell leads the service's fisheries law enforcement in the Pacific. "Every single one of these countries that we’re concerned about is in our backyard."

The joint patrols are fueled, too, by U.S. concerns about China, which maintains the largest fishing fleet in the world and has invested heavily in port access in coastal nations from Latin America to West Africa.

Hundreds of Chinese fishing vessels have swarmed the high seas near South America, with the Argentine navy twice firing shots at Chinese boats in 2018 and 2019. Last summer, the AP discovered that two dozen Chinese vessels fishing near the Galapagos Islands had a history of labor abuse accusations, past convictions for illegal fishing or showed signs of possibly violating maritime law.

Meanwhile, China and its neighbors in the South China Sea are at a long-running standoff over access to islands and fishing grounds. The conflict has flared between coast guards and foreign fishing crews in the Paracel Islands near Vietnam, the Natuna Islands near Indonesia, and the Spratly Islands west of the Philippines.

"It’s a tinderbox," said Sally Yozell, a senior fellow at the Stimson Center, a national security think tank based in Washington.

The AP reviewed data from the Center for Strategic and International Studies, which tracked armed standoffs in the South China Sea from 2010 through 2020. More than three-quarters of the 17 events since 2017 involved violence between a law enforcement vessel and a foreign fishing crew.

The conflicts show that fishing and national security concerns are increasingly intertwined.

China maintains a fleet of maritime militia fishing boats, for instance, that can store weapons and water cannons alongside their catch, according to research by CSIS and the Center for Advanced Defense Studies. A separate fleet of fishing boats lingers near the disputed Spratly Islands, serving as an implicit extension of Chinese law enforcement.

Neither fleet does much fishing, said Gregory Poling, director of the Asia Maritime Transparency Initiative at CSIS. Mainly, he said, the boats stay put, anchored – achieving a larger political goal.

"Nobody’s crazy enough to try to board a Chinese boat surrounded by a hundred other Chinese boats, all of whom are bigger than you."

Even Chinese boats that do fish commercially are often escorted by armed coast guard vessels, Poling said.

The U.S. Coast Guard has accused China’s maritime militia of "aggressive behavior" meant to intimidate foreign fishermen at home and on the high seas.

For many countries, violent confrontations at sea are a last-ditch effort to keep foreign fleets from fishing illegally.

Countries like Indonesia, Malaysia and Australia try to deter illegal fishing by making a spectacle of their enforcement, lining confiscated boats with explosives, and setting them aflame.

Indonesia sank more than 370 foreign fishing boats in the past five years, according to the Ministry of Marine Affairs and Fisheries.

Andreas Aditya Salim, the co-founder of the Indonesia Ocean Justice Initiative and a former member of the fishing ministry, said seeing his country destroying foreign fishing boats felt "heroic." As a nation comprising more than 17,000 islands, Indonesia has far more marine territory than land.

"This is important for my country. We have to defend it," he said. The explosions send a message that "illegal fishing stops here."

But elsewhere in the Indian Ocean, it is Indonesian boats that are being destroyed. Last fall, Australia’s Border Force destroyed three Indonesian fishing boats and posted pictures on Facebook of a vessel on fire.

Authorities destroyed at least 15 foreign fishing boats between July and October last year, part of a task force operation to combat rising incursions.

"Our message to foreign fishers that choose to fish outside the rules is simple," the Border Force said in a statement last year. "We will intercept you, you will lose your catch, your equipment and possibly even your vessel."

The U.S. Coast Guard has taken a much quieter approach to dispose of Mexican fishing boats captured in U.S. waters. At the South Padre Island station in Texas, 440 boats were cut apart over the past five years, the Coast Guard said – their engines crushed.

The Canadian Coast Guard and the Fisheries Control Agency for the European Union both told the AP they had not rammed or shot at a foreign fishing boat in that timeframe. Still, Europe has not been immune to conflict, with press reports describing Romanian authorities firing at a Turkish boat suspected of illegal fishing, and Italian law enforcement chasing and shooting at a Tunisian fishing boat.

Feuds at sea were common before the United Nations established a broader international agreement on maritime boundaries in 1982. The Americas were no exception.

In the late sixties, a U.S. tuna boat was hit by machine-gun fire for fishing in Peru’s claimed economic waters. The U.S. and Canada also argued for years over the right to fish around Georges Bank, a rich scallop ground between Nova Scotia and Maine, until the dispute was settled in the international court in 1984.

Some experts say climate change could be the next driver of armed conflicts between nations overfishing.

Bergenas, who is working to predict the next areas of fishing conflict, has his eyes trained on the Arctic and the tropical Pacific.

Polar ice melting could free up valuable fisheries for Russia, China and the United States, he said, and he expects Pacific tuna stocks to migrate eastward, leaving poverty and bitter competition in their wake.

Where lines of demarcation between nations remain unclear or international relations are fraught, fishing serves as an easy spark for conflict. Last year, Eritrean military forces opened fire at Yemeni fishermen near the Hanish Islands, reviving a conflict over the contested area that started decades ago. And off the coast of the Gaza Strip, Palestinian fishermen have been in constant conflict with Israeli security forces.

The AP, drawing on data from the nonprofit Armed Conflict Location and Event Data Project, found more than 300 incidents of Israeli authorities firing shots, damaging vessels or shooting water cannons at Gaza fishermen in the past five years.

The tight control Israel keeps over Gaza’s borders has meant Palestinians are restricted to fishing in a narrow ribbon of the Mediterranean Sea, and in wartime, Israel has cut off access to the fishing zone altogether. The Israeli Defense Forces did not respond to AP’s requests for comment but have previously said the restrictions are a security measure to prevent the militant group Hamas from launching attacks in Israel.

Nizar Ayyash, head of Gaza’s fishermen union, told the AP three fishermen have died from attacks in the past five years. The best fishing is for sea bass, he said, but stocks are mostly located outside the permitted area.

Most shootings happen within 100-200 meters of fishing boundaries to the north and south, Ayyash said, though organizations like Gisha and the Palestinian Center for Human Rights have documented attacks well within areas where Gaza’s fishermen were allowed to work.

"Fishing has become a far more dangerous occupation and also one that fewer Gaza residents can make a living off of because of the problems in accessing Gaza’s sea space," said Miriam Marmur, Gisha’s public advocacy director.

The violence between Sri Lanka and India persists despite the countries’ otherwise friendly relations. Many Indian and Sri Lankan fishermen share the same Tamil ethnicity and language, even if their countries sit opposite a narrow band of the ocean.

Yet Sri Lankan authorities say Indian trawlers pose a real threat to the country’s fishing sector. Sri Lanka has banned bottom trawling, a practice environmentalists say strips the sea of fish and damages seaweed and coral reefs.

Bottom trawling "is bad enough," said V. Vivekanandan, former head of the South Indian Federation of Fisherman Societies. Subsequent innovations are even worse, he said, allowing the nets to catch "every fish available in the sea."

Decades of civil war in Sri Lanka meant that Indian crews could reap the benefits of fishing in the waters around the island without repercussion, but the war’s end in 2009 and the return of Sri Lankan fishermen to the sea pushed fishing conflicts back into the limelight.

Deadly brawls have erupted between the competing boats even when national authorities aren’t present. Herman Kumara, head of Sri Lanka’s National Fisheries Solidarity Movement, said seven Sri Lankan fishermen died amid violence with Indian crews in 2019. Another two died this year.

Kumara wants to see even stronger enforcement and hopes for a dialogue with Indian fishermen.

"It has already turned violent," he said. Without intervention, he added, "this situation might explode."